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1
Özer, Ömer. « Investigation of Strength, Flexibility and Balance Parameters with Performance Dimension in Basketball Players ». Journal of Education and Learning 8, no 5 (20 septembre 2019) : 225. http://dx.doi.org/10.5539/jel.v8n5p225.
Texte intégralRésumé :
The aim of this study is to investigate the relationship between strength, flexibility and balance parameters of male basketball players with performance dimension. Sixteen elite basketball players participated in the study voluntarily. Leg and back strength, flexibility and static and dynamic balance parameters of the participants were examined. Pearson Product Moment Correlation Coefficient method was used to determine the relationship between performance values obtained from strength, flexibility and balance parameters. As a result of the analysis of the data obtained; between LS and BS (r = 0.676 p < 0.01), SBRL and SBB (r = 0.787 p < 0.01), SBLL and SBB and SBRL (r = 0.688 p < 0.01, r = 0.791 p < 0.01), DBB and SBB and SBRL (r = 0.775 p < 0.01, r = 0.752 p < 0.01), DBRL and SBB, SBRL, SBLL and DBB (r = 0.800 p < 0.01, r = 0.694 p < 0.01, r = 0.707 p < 0.01, r = 0.874 p < 0.01), DBLL and SBB and SBRL (r = 0.765 p < 0.01, r = 0.652 p < 0.01) are high related. Whiler there was a moderate relationship between DBB and SBLL(r = 0.610 p < 0.05), DBRL and SBRL, DBB and DBRL (r = 0.588 p < 0.05, r = 0.589 p < 0.05, r = 0.566 p < 0.05), there were no relationship between FLX and LS and BS(r = 0.430 p > 0.05, r = 0.155 p > 0.05), SDİ SBB and LS, BS and FLX (r = 0.341 p > 0.05, r = 0.388 p > 0.05, r = 0.274 p > Z0.05), SDSA SBRL and LS, BS and FLX (r = 0.103 p > 0.05, r = 0.347 p > 0.05, r = 0.167 p > 0.05), SBLL and LS, BS ve FLX (r = -0.027 p > 0.05, r = 0.237 p > 0.05, r = 0.022 p > 0.05), DBB and LS, BS ve FLX (r = 0.211 p > 0.05, r = 0.306 p > 0.05, r = 0.268 p > 0.05), DBRL and LS, BS and FLX (r = 0.268 p > 0.05, r = 0.433 p > 0.05, r = 0.281 p > 0.05), DBLL and LS, BS and FLX (r = 0.136 p > 0.05, r = 0.137 p > 0.05, r = 0.164 p > 0.05). As a result, it is thought that the basketball players’ performance will be increased by paying attention to the content of training programs due to the sudden direction change actions of basketball, which are related to strength, flexibility and balance parameters of male basketball players.
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Yu, Jiabao, Jiawei Chen, Ying Chen, Zhiguo Zhou et Junwei Duan. « Double Broad Reinforcement Learning Based on Hindsight Experience Replay for Collision Avoidance of Unmanned Surface Vehicles ». Journal of Marine Science and Engineering 10, no 12 (18 décembre 2022) : 2026. http://dx.doi.org/10.3390/jmse10122026.
Texte intégralRésumé :
Although broad reinforcement learning (BRL) provides a more intelligent autonomous decision-making method for the collision avoidance problem of unmanned surface vehicles (USVs), the algorithm still has the problem of over-estimation and has difficulty converging quickly due to the sparse reward problem in a large area of sea. To overcome the dilemma, we propose a double broad reinforcement learning based on hindsight experience replay (DBRL-HER) for the collision avoidance system of USVs to improve the efficiency and accuracy of decision-making. The algorithm decouples the two steps of target action selection and target Q value calculation to form the double broad reinforcement learning method and then adopts hindsight experience replay to allow the agent to learn from the experience of failure in order to greatly improve the sample utilization efficiency. Through training in a grid environment, the collision avoidance success rate of the proposed algorithm was found to be 31.9 percentage points higher than that in the deep Q network (DQN) and 24.4 percentage points higher than that in BRL. A Unity 3D simulation platform with high fidelity was also designed to simulate the movement of USVs. An experiment on the platform fully verified the effectiveness of the proposed algorithm.
3
Yang, Yibin, Lingxia Zhang et Yu Zhao. « Light Output Enhancement of GaN-Based Light-Emitting Diodes Based on AlN/GaN Distributed Bragg Reflectors Grown on Si (111) Substrates ». Crystals 10, no 9 (1 septembre 2020) : 772. http://dx.doi.org/10.3390/cryst10090772.
Texte intégralRésumé :
Due to the absorption of opaque Si substrates, the luminous efficiency of GaN-based light-emitting diodes (LEDs) on Si substrates is not high. So, in this work, we insert AlN/GaN distributed Bragg reflectors (DBRs) to improve the light output of GaN-based LEDs on Si (111) substrates grown via metal organic chemical vapor deposition (MOCVD). In order to obtain the highest reflectivity of the AlN/GaN DBR stop band, the growth parameters of AlN/GaN DBRs are optimized, including the growth temperature, the V/III ratio and the growth pressure. As a consequence, the interfaces of the optimal 9-pair AlN/GaN DBRs become abrupt, and the reflectivity of the DBR stop band is as high as 85.2%, near to the calculated value (92.5%). Finally, crack-free GaN-based LEDs with 5-pair AlN/GaN DBRs are grown on Si (111) substrates. The light output of the DBR-based LED is evidently enhanced by 41.8% at the injection current of 350 mA, compared with the conventional DBR-based LED without DBRs. These results pave the way for the luminous efficiency improvement of future green and red GaN-based LEDs grown on Si substrates.
4
Zhang, Cheng, Rami ElAfandy et Jung Han. « Distributed Bragg Reflectors for GaN-Based Vertical-Cavity Surface-Emitting Lasers ». Applied Sciences 9, no 8 (17 avril 2019) : 1593. http://dx.doi.org/10.3390/app9081593.
Texte intégralRésumé :
A distributed Bragg reflector (DBR) is a key building block in the formation of semiconductor microcavities and vertical cavity surface emitting lasers (VCSELs). The success in epitaxial GaAs DBR mirrors paved the way for the ubiquitous deployment of III-V VCSELs in communication and mobile applications. However, a similar development of GaN-based blue VCSELs has been hindered by challenges in preparing DBRs that are mass producible. In this article, we provide a review of the history and current status of forming DBRs for GaN VCSELs. In general, the preparation of DBRs requires an optimization of epitaxy/fabrication processes, together with trading off parameters in optical, electrical, and thermal properties. The effort of epitaxial DBRs commenced in the 1990s and has evolved from using AlGaN, AlN, to using lattice-matched AlInN with GaN for DBRs. In parallel, dielectric DBRs have been studied since 2000 and have gone through a few design variations including epitaxial lateral overgrowth (ELO) and vertical external cavity surface emitting lasers (VECSEL). A recent trend is the use of selective etching to incorporate airgap or nanoporous GaN as low-index media in an epitaxial GaN DBR structure. The nanoporous GaN DBR represents an offshoot from the traditional epitaxial approach and may provide the needed flexibility in forming manufacturable GaN VCSELs. The trade-offs and limitations of each approach are also presented.
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Al-Dulaijan, Yousif A., et Abdulrahman A. Balhaddad. « Prospects on Tuning Bioactive and Antimicrobial Denture Base Resin Materials : A Narrative Review ». Polymers 15, no 1 (23 décembre 2022) : 54. http://dx.doi.org/10.3390/polym15010054.
Texte intégralRésumé :
Denture base resin (DBR) materials are used in dentistry in constructing removable dentures and implant-supported prostheses. A plethora of evidence has demonstrated that DBR materials are associated with a high risk of denture stomatitis, a clinical complication where the soft oral tissues underneath the resin-based material are inflamed. The prevalence of denture stomatitis among denture wearers is high worldwide. Plaque accumulation and the infiltration of oral microbes into DBRs are among the main risk factors for denture stomatitis. The attachment of fungal species, mainly Candida albicans, to DBRs can irritate the underneath soft tissues, leading to the onset of the disease. As a result, several attempts were achieved to functionalize antimicrobial compounds and particles into DBRs to prevent microbial attachment. This review article explored the advanced approaches in designing bioactive and antimicrobial DBR materials. It was reported that using monomer mixtures, quaternary ammonium compounds (QACs), and organic and inorganic particles can suppress the growth of denture stomatitis-related pathogens. This paper also highlighted the importance of characterizing bioactive DBRs to be mechanically and physically sustainable. Future directions may implement a clinical translational model to attempt these materials inside the oral cavity.
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Breiland, W. G., A. A. Allerman, J. F. Klem et K. E. Waldrip. « Distributed Bragg Reflectors for Vertical-Cavity Surface-Emitting Lasers ». MRS Bulletin 27, no 7 (juillet 2002) : 520–24. http://dx.doi.org/10.1557/mrs2002.170.
Texte intégralRésumé :
AbstractDistributed Bragg reflectors (DBRs) not only serve as high-reflectance mirrors to define the laser cavity of a vertical-cavity surface-emitting laser (VCSEL), but they also must conduct electricity, confine currents, and provide a single-crystal template for the gain region of the laser. Basic optical and electrical properties of DBRs are presented in this article. Three examples of DBR structures used in VCSEL applications from the ultraviolet to the infrared are given to illustrate the complexity and range of materials science issues that are encountered in DBR growth. Fabrication issues are also discussed.
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Abubaker, Shawbo A. « A Comparison of Top Distributed Bragg Reflector for 1300 nm Vertical Cavity Semiconductor Optical Amplifiers Based on III–V Compound ». ARO-THE SCIENTIFIC JOURNAL OF KOYA UNIVERSITY 9, no 2 (28 octobre 2021) : 26–29. http://dx.doi.org/10.14500/aro.10846.
Texte intégralRésumé :
In this work, the design of GaAs/AlGaAs distributed Bragg reflector (DBR) has been implemented for 1300 nm vertical cavity semiconductor optical amplifiers (VCSOAs) for optical fiber communication applications. The top DBR period and Al concentration are varied, the peak reflectivity of the DBR is increasing from 50% to 97.5% for 13 periods with increasing Al concentration, whereas the reflectivity bandwidth is increased to almost 190 nm. The relation between wavelength and incidence angle variation on DBR reflectivity is increasing with the incident angle (0°, 20°, 30°, and 50°), the resonant wavelength and bandwidth of the measured reflectance spectra shifts to shorter wavelength and wider bandwidth, respectively. In addition, a comparison between the linear, the graded, and the parabolic DBRs has been achieved with transfer matrix method using MATLAB software to show the influence of layer in DBRs and its effect on lasing wavelength. It is shown that using grading DBR mirror is much more beneficial compared to abrupt DBR, whereas it has lower reflectivity of almost 10% due to VCSOAs device which needs less number of top layers until prevent reaching lasing threshold.
8
Lu, Xingdong, Jing Li, Kang Su, Chang Ge, Zhicong Li, Teng Zhan, Guohong Wang et Jinmin Li. « Performance-Enhanced 365 nm UV LEDs with Electrochemically Etched Nanoporous AlGaN Distributed Bragg Reflectors ». Nanomaterials 9, no 6 (6 juin 2019) : 862. http://dx.doi.org/10.3390/nano9060862.
Texte intégralRésumé :
A 365-nm UV LED was fabricated based on embedded nanoporous AlGaN distributed Bragg reflectors (DBR) by electrochemical etching. The porous DBR had a reflectance of 93.5% at the central wavelength of 365 nm; this is the highest value of porous AlGaN DBRs below 370 nm which has been reported so far. An innovative two-step etching method with a SiO2 sidewall protection layer (SPL) was proposed to protect the n-AlGaN layer and active region of UV LED from being etched by the electrolyte. The DBR-LED with SPL showed 54.3% improvement of maximal external quantum efficiency (EQE) and 65.7% enhancement of optical power at 100 mA without any degeneration in electrical properties, compared with the un-etched standard LED sample. This work has paved the way for the application of electrically-pumped UV LEDs and VCSELs based on nanoporous AlGaN DBRs.
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Wang, Qi, Hai Na Mo, Zi Qiao Lou, Ke Meng Yang, Yue Sun, Yuan Jun He et De Yuan Chen. « Effects of One-Dimensional Photonic Crystal on Thin Film Silicon Solar Cells ». Advanced Materials Research 827 (octobre 2013) : 49–53. http://dx.doi.org/10.4028/www.scientific.net/amr.827.49.
Texte intégralRésumé :
We have designed lateral contact thin film silicon-based solar cells with and without one-dimensional photonic crystals as back surface field layer. The photonic crystal comprises a distributed Bragg reflector (DBR) for trapping the light. Simulations demonstrate that energy conversion efficiency and short circuit current ISCfor c-Si solar cells with the photonic crystal structure are increased to 21.11% and 27.0 mA, respectively, from 18.33% and 22.8mA of the one without photonic crystal. In addition, the effects of DBRs consisting of different materials are investigated in our simulations. When the refractive index difference between sub-layers of the DBR is larger, the forbidden band width is broader, the reflectance of the DBR is higher, and more photons are reflected and trapped into the active region, then the absorption efficiency and the energy conversion efficiency of the solar cell are both increased. The bigger the refractive index difference of the DBRs sub-layers is, the broader the forbidden band width is. In addition, a-Si solar cells with and without DBR are also discussed.
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Hamaguchi, Tatsushi, Hiroshi Nakajima et Noriyuki Fuutagawa. « GaN-based Vertical-Cavity Surface-Emitting Lasers Incorporating Dielectric Distributed Bragg Reflectors ». Applied Sciences 9, no 4 (20 février 2019) : 733. http://dx.doi.org/10.3390/app9040733.
Texte intégralRésumé :
This paper reviews past research and the current state-of-the-art concerning gallium nitride-based vertical-cavity surface-emitting lasers (GaN-VCSELs) incorporating distributed Bragg reflectors (DBRs). This paper reviews structures developed during the early stages of research into these devices, covering both major categories of GaN-based VCSELs: hybrid-DBR and all-dielectric-DBR. Although both types exhibited satisfactory performance during continuous-wave (CW) operation in conjunction with current injection as early as 2008, GaN-VCSELs have not yet been mass produced for several reasons. These include the difficulty in controlling the thicknesses of nitride semiconductor layers in hybrid-DBR type devices and issues related to the cavity dimensions in all-dielectric-DBR units. Two novel all-dielectric GaN-based VCSEL concepts based on different structures are examined herein. In one, the device incorporates dielectric DBRs at both ends of the cavity, with one DBR embedded in n-type GaN grown using the epitaxial lateral overgrowth technique. The other concept incorporates a curved mirror fabricated on (000-1) GaN. Both designs are intended to mitigate challenges regarding industrial-scale processing that are related to the difficulty in controlling the cavity length, which have thus far prevented practical applications of all-dielectric GaN-based VCSELs.
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Białek, Ewelina, Maksymilian Włodarski et Małgorzata Norek. « Fabrication of Porous Anodic Alumina (PAA) by High-Temperature Pulse-Anodization : Tuning the Optical Characteristics of PAA-Based DBR in the NIR-MIR Region ». Materials 13, no 24 (9 décembre 2020) : 5622. http://dx.doi.org/10.3390/ma13245622.
Texte intégralRésumé :
In this work, the influence of various electrochemical parameters on the production of porous anodic alumina (PAA)-based DBRs (distributed Bragg reflector) during high-temperature-pulse-anodization was studied. It was observed that lowering the temperature from 30 to 27 °C brings about radical changes in the optical performance of the DBRs. The multilayered PAA fabricated at 27 °C did not show optical characteristics typical for DBR. The DBR performance was further tuned at 30 °C. The current recovery (iamax) after application of subsequent UH pulses started to stabilize upon decreasing high (UH) and low (UL) voltage pulses, which was reflected in a smaller difference between initial and final thickness of alternating dH and dL segments (formed under UH and UL, respectively) and a better DBR performance. Shortening UH pulse duration resulted in a progressive shift of photonic stopbands (PSBs) towards the blue part of the spectrum while keeping intensive and symmetric PSBs in the NIR-MIR range. Despite the obvious improvement of the DBR performance by modulation of electrochemical parameters, the problem regarding full control over the homogeneous formation of dH+dL pairs remains. Solving this problem will certainly lead to the production of affordable and efficient PAA-based photonic crystals with tunable photonic properties in the NIR-MIR region.
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Lee, Hyung-Joo, Jin-Young Park, Lee-Ku Kwac et Jongsu Lee. « Improvement of Near-Infrared Light-Emitting Diodes’ Optical Efficiency Using a Broadband Distributed Bragg Reflector with an AlAs Buffer ». Nanomaterials 14, no 4 (12 février 2024) : 349. http://dx.doi.org/10.3390/nano14040349.
Texte intégralRésumé :
This study developed an advanced 850 nm centered distributed Bragg reflector (DBR) (broadband DBR) composed of nanomaterial-based multiple structures to improve the optical efficiency of an 850 nm near-infrared light-emitting diode (NIR-LED). A combined 850 nm centered broadband DBR was fabricated by growing an 800 nm centered ten-pair DBR on a 900 nm centered ten-pair DBR (denoted as a combined DBR). The combined DBR exhibited a slightly wider peak band than conventional DBRs. Furthermore, the peak band width of the combined DBR significantly increased upon using a reflective AlAs buffer layer that reduced the overlapped reflection. The output power (20.5 mW) of NIR-LED chips using the combined DBR with an AlAs buffer layer exceeded that of a conventional 850 nm centered DBR (14.5 mW) by more than 40%. Results indicated that combining the optical conditions of wavelengths and the AlAs buffer layer effectively strengthened the broadband effect of the DBR and increased the optical efficiency of the 850 nm NIR-LED.
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Sun, Yuechang, Lang Shi, Peng Du, Xiaoyu Zhao et Shengjun Zhou. « Rational Distributed Bragg Reflector Design for Improving Performance of Flip-Chip Micro-LEDs ». Electronics 11, no 19 (23 septembre 2022) : 3030. http://dx.doi.org/10.3390/electronics11193030.
Texte intégralRésumé :
The distributed Bragg reflector (DBR) has been widely used in flip-chip micro light-emitting diodes (micro-LEDs) because of its high reflectivity. However, the conventional double-stack DBR has a strong angular dependence and a narrow reflective bandwidth. Here, we propose a wide reflected angle Ti3O5/SiO2 DBR (WRA-DBR) for AlGaInP-based red and GaN-based green/blue flip-chip micro-LEDs (RGB flip-chip micro-LEDs) to overcome the drawbacks of the double-stack DBR. The WRA-DBR consisting of six sub-DBRs has high reflectivity within the visible light wavelength region at an incident angle of light ranging from 0° to 60°. Furthermore, the influence of the WRA-DBR and double-stack DBR on performances of RGB flip-chip micro-LEDs is numerically investigated based on the finite-difference time-domain method. Owing to higher reflectivity and less angular dependence of the WRA-DBR, the RGB flip-chip micro-LEDs with the WRA-DBR have a stronger electric field intensity in the top side in comparison with RGB flip-chip micro-LEDs with the double-stack DBR, which indicates that more photons can be extracted from micro-LEDs with the WRA-DBR.
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Verma, Nivea, et Manesh Lahori. « Effect of Chitosan on the Mechanical Properties and Color Stability of Two Commercially Available Heat Cure Denture Base Resins : An In vitro Study ». Journal of Interdisciplinary Dentistry 13, no 3 (2023) : 143–52. http://dx.doi.org/10.4103/jid.jid_31_23.
Texte intégralRésumé :
ABSTRACT Background: Chitosan is one of the new and promising biomaterials being used in dentistry. However, there are fewer studies available in the literature to estimate the mechanical properties of chitosan with heat polymerized denture base resin (DBR). This study aimed to evaluate the effect of incorporation of chitosan nanoparticles on flexural strength, fracture toughness, and color stability of two different types of heat cure DBR. Aim: The aim of the study is to evaluate the mechanical properties and color stability of two DBRs reinforced with different concentrations of chitosan. Materials and Methods: A total of 240 samples were made of DPI (n = 120) and Trevalon (n = 120) DBR. The samples of each type were divided into four groups depending on the concentration of chitosan-C 0, C 5, C 12.5, and C 20. Flexural strength and fracture toughness were estimated with a universal testing machine. Spectrophotometer was used to evaluate the color stability. Statistical Analysis: Results were compared with one-way analysis of variance, post hoc Tukey honest significant difference test, and Student’s t-test. Results: The results of the study showed that chitosan-reinforced DBR displayed enhanced mechanical properties. The test group with 5% chitosan nanoparticles had optimum mechanical properties among different test groups for both the DBR. The values for flexural strength and fracture toughness decreased with an increase in the percentage of chitosan. The addition of chitosan to DPI and Trevalon DBRs showed visible color change. Conclusion: The study concluded the Trevalon DBR with 5% chitosan showed the highest flexural strength and fracture toughness values. The addition of chitosan nanoparticles had no significant negative effects on heat-cure acrylic resin’s color change property. CLINICAL RELEVANCE TO INTERDISCIPLINARY DENTISTRY Gives knowledge about the mechanical properties as well as the physical properties of denture base resin which is beneficial for the dentists.
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Huang, Chia-Yen, Kuo-Bin Hong, Zhen-Ting Huang, Wen-Hsuan Hsieh, Wei-Hao Huang et Tien-Chang Lu. « Challenges and Advancement of Blue III-Nitride Vertical-Cavity Surface-Emitting Lasers ». Micromachines 12, no 6 (9 juin 2021) : 676. http://dx.doi.org/10.3390/mi12060676.
Texte intégralRésumé :
Since the first demonstration of (Al, In, Ga)N-based blue vertical-cavity surface-emitting lasers (VCSELs) in 2008, the maximum output power (Pmax) and threshold current density (Jth) has been improved significantly after a decade of technology advancements. This article reviewed the key challenges for the realization of VCSELs with III-nitride materials, such as inherent polarization effects, difficulties in distributed Bragg’s reflectors (DBR) fabrication for a resonant cavity, and the anti-guiding effect due to the deposited dielectrics current aperture. The significant tensile strain between AlN and GaN hampered the intuitive cavity design with two epitaxial DBRs from arsenide-based VCSELs. Therefore, many alternative cavity structures and processing technologies were developed; for example, lattice-matched AlInN/GaN DBR, nano-porous DBR, or double dielectric DBRs via various overgrowth or film transfer processing strategies. The anti-guiding effect was overcome by integrating a fully planar or slightly convex DBR as one of the reflectors. Special designs to limit the emission polarization in a circular aperture were also summarized. Growing VCSELs on low-symmetry non-polar and semipolar planes discriminates the optical gain along different crystal orientations. A deliberately designed high-contrast grating could differentiate the reflectivity between the transverse-electric field and transverse-magnetic field, which restricts the lasing mode to be the one with the higher reflectivity. In the future, the III-nitride based VCSEL shall keep advancing in total power, applicable spectral region, and ultra-low threshold pumping density with the novel device structure design and processing technologies.
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Shao, Weijia, et Tingting Liu. « Planar narrowband Tamm plasmon-based hot-electron photodetectors with double distributed Bragg reflectors ». Nano Express 2, no 4 (22 novembre 2021) : 040009. http://dx.doi.org/10.1088/2632-959x/ac396b.
Texte intégralRésumé :
Abstract Hot-electron photodetectors (HE PDs) are attracting a great deal of attention from plasmonic community. Many efficient HE PDs with various plasmonic nanostructures have been demonstrated, but their preparations usually rely on complicated and costly fabrication techniques. Planar HE PDs are viewed as potential candidates of cost-effective and large-area applications, but they likely fail in the simultaneous achievement of outstanding optical absorption and hot-electron collection. To reconcile the contradiction between optical and electrical requirements, herein, we propose a planar HE PD based on optical Tamm plasmons (TPs) consisted of an ultrathin gold film (10 nm) sandwiched between two distributed Bragg reflectors (DBRs). Simulated results show that strong optical absorption (>0.95) in the ultrathin Au film is realized. Electrical calculations show that the predicted peak photo-responsivity of proposed HE PD with double DBRs is over two times larger than that of conventional single-DBR HE PD. Moreover, the planar dual-DBR HE PDs exhibit a narrowband photodetection functionality and sustained performance under oblique incidences. The optical nature associated with TP resonance is elaborated.
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Zhao, Shu-Yu, Bin-Bin Xu, Zhen-Yu Zhao et Xue-Qin Lü. « Influence of top mirror on performance of GaN-based resonant cavity light-emitting diode ». Acta Physica Sinica 71, no 4 (2022) : 047801. http://dx.doi.org/10.7498/aps.71.20211720.
Texte intégralRésumé :
In this paper, two kinds of distributed Bragg reflectors (DBRs) with high-reflective-film structure and filter structure are designed and evaporated on the top of GaN-based resonant cavity light emitting diode (RCLED), respectively. Firstly, the reflectivity spectra of the two kinds of DBRs are simulated. Then, the differences in performance including optical longitudinal modes, spectral linewidth, and output light intensity between the two kinds of RCLED devices with different top mirrors, are compared and analyzed. Finally, the influence of the top mirror reflection characteristics on the output spectrum of the RCLED is studied in detail. The results show that the top mirror is an important part of RCLED, and its reflection characteristics determine the optical performance of the device. For the conventional DBR with high-reflective-film structure, its reflectivity spectrum has a wide high-reflection band. Accordingly, the spectral linewidth of the RCLED can be effectively narrowed by using the conventional DBR as the top mirror. However, the spectrum still consists of multi-longitudinal modes. For the DBR with filter structure, its reflectivity spectrum has a narrow high-transmittance band at the central wavelength. Depending on the modulation effect of the high-transmittance band to the output light, single longitudinal mode light emission is realized for the RCLED with the specially designed DBR as the top mirror, which shows a broad application prospect in optical communication and optical fiber sensing. Moreover, the spectral characteristics of the RCLED can be further optimized to meet its application requirements in much more fields, by designing the top mirror structure and changing its reflectivity spectrum characteristics.
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Shih, Ching-Wen, Imad Limame, Sebastian Krüger, Chirag C. Palekar, Aris Koulas-Simos, Daniel Brunner et Stephan Reitzenstein. « Low-threshold lasing of optically pumped micropillar lasers with Al0.2Ga0.8As/Al0.9Ga0.1As distributed Bragg reflectors ». Applied Physics Letters 122, no 15 (10 avril 2023) : 151111. http://dx.doi.org/10.1063/5.0143236.
Texte intégralRésumé :
We report on the design, realization, and characterization of optically pumped micropillar lasers with low-absorbing Al0.2Ga0.8As/Al0.9Ga0.1As dielectric Bragg reflectors (DBRs) instead of commonly used GaAs/AlGaAs DBRs. A layer of (In, Ga)As quantum dots is embedded in the GaAs [Formula: see text]-cavity of as an active medium. We experimentally study the lasing characteristics of the fabricated micropillars by means of low-temperature photoluminescence with varying pump laser wavelength between 532 and 899 nm. The incorporation of 20% Al content in the DBRs opens an optical pumping window from 700 to 820 nm, where the excitation laser light can effectively reach the GaAs cavity above its bandgap while remaining transparent to the DBRs. This results in a substantially improved pump efficiency, a low lasing threshold, and a high thermal stability. Pump laser wavelengths outside of the engineered spectral window lead to low pump efficiency due to strong absorption by the top DBR or inefficient excitation of pump-level excitons. The superiority of the absorption-free modified DBRs is demonstrated by simply switching the pump laser wavelength from 671 to 708 nm, which crosses the DBRs absorption edge and drastically reduces the lasing threshold by more than an order of magnitude from (363.5 [Formula: see text] 18.5) to (12.8 [Formula: see text] 0.3) [Formula: see text]W.
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Aghaeipour, Mahtab, et Håkan Pettersson. « Enhanced broadband absorption in nanowire arrays with integrated Bragg reflectors ». Nanophotonics 7, no 5 (24 mai 2018) : 819–25. http://dx.doi.org/10.1515/nanoph-2017-0101.
Texte intégralRésumé :
AbstractA near-unity unselective absorption spectrum is desirable for high-performance photovoltaics. Nanowire (NW) arrays are promising candidates for efficient solar cells due to nanophotonic absorption resonances in the solar spectrum. The absorption spectra, however, display undesired dips between the resonance peaks. To achieve improved unselective broadband absorption, we propose to enclose distributed Bragg reflectors (DBRs) in the bottom and top parts of indium phosphide (InP) NWs, respectively. We theoretically show that by enclosing only two periods of In0.56Ga0.44As/InP DBRs, an unselective 78% absorption efficiency (72% for NWs without DBRs) is obtained at normal incidence in the spectral range from 300 nm to 920 nm. Under oblique light incidence, the absorption efficiency is enhanced up to about 85% at an incidence angle of 50°. By increasing the number of DBR periods from two to five, the absorption efficiency is further enhanced up to 95% at normal incidence. In this work, we calculated optical spectra for InP NWs, but the results are expected to be valid for other direct band gap III–V semiconductor materials. We believe that our proposed idea of integrating DBRs in NWs offers great potential for high-performance photovoltaic applications.
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Białek, Ewelina, Maksymilian Włodarski et Małgorzata Norek. « Influence of Anodization Temperature on Geometrical and Optical Properties of Porous Anodic Alumina(PAA)-Based Photonic Structures ». Materials 13, no 14 (16 juillet 2020) : 3185. http://dx.doi.org/10.3390/ma13143185.
Texte intégralRésumé :
In this work, the influence of a wide range anodizing temperature (5–30 °C) on the growth and optical properties of PAA-based distributed Bragg reflector (DBR) was studied. It was demonstrated that above 10 °C both structural and photonic properties of the DBRs strongly deteriorates: the photonic stop bands (PSBs) decay, broaden, and split, which is accompanied by the red shift of the PSBs. However, at 30 °C, new bands in transmission spectra appear including one strong and symmetric peak in the mid-infrared (MIR) spectral region. The PSB in the MIR region is further improved by a small modification of the pulse sequence which smoothen and sharpen the interfaces between consecutive low and high refractive index layers. This is a first report on PAA-based DBR with a good quality PSB in MIR. Moreover, it was shown that in designing good quality DBRs a steady current recovery after subsequent application of high potential (UH) pulses is more important than large contrast between low and high potential pulses (UH-UL contrast). Smaller UH-UL contrast helps to better control the current evolution during pulse anodization. Furthermore, the lower PSB intensity owing to the smaller UH-UL contrast can be partially compensated by the higher anodizing temperature.
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Tzanakakis, Emmanouil-George, Panagiotis Pandoleon, Aspasia Sarafianou et Eleana Kontonasaki. « Adhesion of Conventional, 3D-Printed and Milled Artificial Teeth to Resin Substrates for Complete Dentures : A Narrative Review ». Polymers 15, no 11 (28 mai 2023) : 2488. http://dx.doi.org/10.3390/polym15112488.
Texte intégralRésumé :
Background: One type of failure in complete or partial dentures is the detachment of resin teeth from denture base resin (DBR). This common complication is also observed in the new generation of digitally fabricated dentures. The purpose of this review was to provide an update on the adhesion of artificial teeth to denture resin substrates fabricated by conventional and digital methods. Methods: A search strategy was applied to retrieve relevant studies in PubMed and Scopus. Results: Chemical (monomers, ethyl acetone, conditioning liquids, adhesive agents, etc.) and mechanical (grinding, laser, sandblasting, etc.) treatments are commonly used by technicians to improve denture teeth retention with controversial benefits. Better performance in conventional dentures is realized for certain combinations of DBR materials and denture teeth after mechanical or chemical treatment. Conclusions: The incompatibility of certain materials and lack of copolymerization are the main reasons for failure. Due to the emerging field of new techniques for denture fabrication, different materials have been developed, and further research is needed to elaborate the best combination of teeth and DBRs. Lower bond strength and suboptimal failure modes have been related to 3D-printed combinations of teeth and DBRs, while milled and conventional combinations seem to be a safer choice until further improvements in printing technologies are developed.
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Frimpong-Manso, Ellen Serwaa, et Liancheng Wang. « High Reflectivity AlN/Al1−xInxN Distributed Bragg Reflectors across the UV Regions by Sputtering ». Crystals 12, no 2 (24 janvier 2022) : 162. http://dx.doi.org/10.3390/cryst12020162.
Texte intégralRésumé :
To improve the performance of III-nitride compound semiconductor-based optoelectronic devices, highly reflective distributed Bragg reflectors (DBRs) are a requirement. In this report, AlN and Al1−xInxN layers were first sputtered and characterized concerning their optical, structural and morphological properties. Ellipsometry measurements were used to determine the optical constants (refractive index, n and coefficient of extinction, k, in dependence of the wavelengths of the layers. The indium content of the Al1−xInxN film was investigated by X-ray photoelectron spectroscopy analysis. Subsequently, AlN/Al1−xInxN DBRs with high reflectivity spectra operating in the UV A, B and C were designed and fabricated on Si (111) and SiO2 substrates by radio frequency (RF) magnetron sputtering. The DBRs consist of an eight-pair AlN/Al0.84In0.16N at 235 nm, 290 nm and 365 nm with reflectances of 86.5%, 97.7% and 97.5% with FWHM of 45 nm, 70 nm and 96 nm, respectively. Atomic force microscopy analysis yielded a Root Mean Square (RMS) of 2.95 nm, implying that the DBR samples can achieve reasonable smoothness over a wide area. Furthermore, the impact of an annealing phase, which is frequently required during device growth, was investigated. Our findings indicate that AlN and Al1−xInxN are suitable materials for the fabrication of deep UV DBRs.
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Ra, Yong-Ho, Roksana Tonny Rashid, Xianhe Liu, Sharif Md Sadaf, Kishwar Mashooq et Zetian Mi. « An electrically pumped surface-emitting semiconductor green laser ». Science Advances 6, no 1 (janvier 2020) : eaav7523. http://dx.doi.org/10.1126/sciadv.aav7523.
Texte intégralRésumé :
Surface-emitting semiconductor lasers have been widely used in data communications, sensing, and recently in Face ID and augmented reality glasses. Here, we report the first achievement of an all-epitaxial, distributed Bragg reflector (DBR)–free electrically injected surface-emitting green laser by exploiting the photonic band edge modes formed in dislocation-free gallium nitride nanocrystal arrays, instead of using conventional DBRs. The device operates at ~523 nm and exhibits a threshold current of ~400 A/cm2, which is over one order of magnitude lower compared to previously reported blue laser diodes. Our studies open a new paradigm for developing low-threshold surface-emitting laser diodes from the ultraviolet to the deep visible (~200 to 600 nm), wherein the device performance is no longer limited by the lack of high-quality DBRs, large lattice mismatch, and substrate availability.
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Lin, Chiao-Chih, Pei-Wen Chan, Peter Chen, Zong Yu Wu, Hsu-Cheng Hsu, Wei-Chih Lai et Yu-Hsun Chou. « Controlled Cavity Length and Wide-Spectrum Lasing in FAMACsPb(BrI)3 Ternary Perovskite Vertical-Cavity Surface-Emitting Lasers with an All-Dielectric Dielectric Bragg Reflector ». Crystals 13, no 10 (19 octobre 2023) : 1517. http://dx.doi.org/10.3390/cryst13101517.
Texte intégralRésumé :
In this study, we utilized a dielectric Bragg reflector (DBR) as a mirror and positioned a wide-spectrum FAMACsPb(BrI)3 halide perovskite film between two DBRs to construct a vertical-cavity surface-emitting laser (VCSEL) structure. The top and bottom DBRs were connected using optical adhesive, allowing us to control the cavity length by applying external force. Through this approach, we achieved operation at the desired wavelength. Due to the exceptional optical gain provided by FAMACsPb(BrI)3, we successfully observed multimode and lasing phenomena at room temperature under continuous-wave (CW) laser excitation. The outcomes of this study provide valuable insights for the application of novel VCSEL structures and highlight the potential of using FAMACsPb(BrI)3 halide perovskites in optical gain. This work holds significant implications for the fields of optical communication and laser technology.
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Mahmoud Ahmed, Naser, M. Roslan Hashim et Hassan Zainuriah. « Effects of Layer Thickness and Incident Angle Variations on DBR Reflectivity ». Materials Science Forum 517 (juin 2006) : 29–32. http://dx.doi.org/10.4028/www.scientific.net/msf.517.29.
Texte intégralRésumé :
In this paper we discussed the relation between depth errors that happened in films growth and incidence angle variation on DBR reflectivity. We assume that there is 10% depth error in high and low index materials, and there are four plus one situations to be considered. Four are combinations of Hi +/- 10% error and Lo +/- 10% error, and no error. Our simulation results show that the depth error makes the reflective band shift and it almost doesn’t reduce reflectivity. The thickness error of +/- 10% in (Al0.4Ga0.6N/GaN) DBR structure (15 pairs) at 420nm was 42nm. A theoretical analysis using Transfer Matrix Mode with MATLAB software on the influence of layer thickness and incidence angle variation in vertical-cavity surface-emitting lasers with distributed Bragg reflectors (DBRs) on lasing wavelength is presented. It is shown that changing the thickness of the layers in the DBR mirror by only 10% is sufficient to produce shifts in the peak reflectance wavelength up to ± 20 nm (for a blue laser at 420nm). This could limit the precision of a desired wavelength, which is its reproducibility.
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Seneza, Cleophace, Christoph Berger, Prabha Sana, Harmut Witte, Jürgen Bläsing, Anja Dempewolf, Armin Dadgar, Jürgen Christen et André Strittmatter. « Highly reflective and conductive AlInN/GaN distributed Bragg reflectors realized by Ge-doping ». Japanese Journal of Applied Physics 61, no 1 (22 décembre 2021) : 015501. http://dx.doi.org/10.35848/1347-4065/ac3d43.
Texte intégralRésumé :
Abstract We report on the realization of highly conductive and highly reflective n-type AlInN/GaN distributed Bragg reflectors (DBR) for use in vertical cavity surface emitters in a metalorganic vapor phase epitaxy process. While Ge-doping enables low-resistive n-type GaN/AlInN/GaN heterostructures, very high Ge doping levels compromise maximum optical reflectivities of DBRs. Simulations of the Bragg mirror’s reflectivities together with structural analysis by X-ray diffraction reveal an increased absorption within the doped AlInN layers and interface roughening as major causes for the observed reduction of the optical reflectivity. By adjusting the Ge doping level in the AlInN layers, this structural degradation was minimized and highly conductive, 45-fold AlInN/GaN DBR structures with a maximum reflectivity of 99% and vertical specific resistance of 5 × 10–4 Ω cm2 were realized.
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Holt, Amanda L., Alison M. Sweeney, Sönke Johnsen et Daniel E. Morse. « A highly distributed Bragg stack with unique geometry provides effective camouflage for Loliginid squid eyes ». Journal of The Royal Society Interface 8, no 63 (16 février 2011) : 1386–99. http://dx.doi.org/10.1098/rsif.2010.0702.
Texte intégralRésumé :
Cephalopods possess a sophisticated array of mechanisms to achieve camouflage in dynamic underwater environments. While active mechanisms such as chromatophore patterning and body posturing are well known, passive mechanisms such as manipulating light with highly evolved reflectors may also play an important role. To explore the contribution of passive mechanisms to cephalopod camouflage, we investigated the optical and biochemical properties of the silver layer covering the eye of the California fishery squid, Loligo opalescens . We discovered a novel nested-spindle geometry whose correlated structure effectively emulates a randomly distributed Bragg reflector (DBR), with a range of spatial frequencies resulting in broadband visible reflectance, making it a nearly ideal passive camouflage material for the depth at which these animals live. We used the transfer-matrix method of optical modelling to investigate specular reflection from the spindle structures, demonstrating that a DBR with widely distributed thickness variations of high refractive index elements is sufficient to yield broadband reflectance over visible wavelengths, and that unlike DBRs with one or a few spatial frequencies, this broadband reflectance occurs from a wide range of viewing angles. The spindle shape of the cells may facilitate self-assembly of a random DBR to achieve smooth spatial distributions in refractive indices. This design lends itself to technological imitation to achieve a DBR with wide range of smoothly varying layer thicknesses in a facile, inexpensive manner.
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Wolffenbuttel, Reinoud, Declan Winship, David Bilby, Jaco Visser, Yutao Qin et Yogesh Gianchandani. « SiNx/SiO2-Based Fabry–Perot Interferometer on Sapphire for Near-UV Optical Gas Sensing of Formaldehyde in Air ». Sensors 24, no 11 (3 juin 2024) : 3597. http://dx.doi.org/10.3390/s24113597.
Texte intégralRésumé :
Fabry–Perot interferometers (FPIs), comprising foundry-compatible dielectric thin films on sapphire wafer substrates, were investigated for possible use in chemical sensing. Specifically, structures comprising two vertically stacked distributed Bragg reflectors (DBRs), with the lower DBR between a sapphire substrate and a silicon-oxide (SiO2) resonator layer and the other DBR on top of this resonator layer, were investigated for operation in the near-ultraviolet (near-UV) range. The DBRs are composed of a stack of nitride-rich silicon-nitride (SiNx) layers for the higher index and SiO2 layers for the lower index. An exemplary application would be formaldehyde detection at sub-ppm concentrations in air, using UV absorption spectroscopy in the 300–360 nm band, while providing spectral selectivity against the main interfering gases, notably NO2 and O3. Although SiNx thin films are conventionally used only for visible and near-infrared optical wavelengths (above 450 nm) because of high absorbance at lower wavelengths, this work shows that nitride-rich SiNx is suitable for near-UV wavelengths. The interplay between spectral absorbance, transmittance and reflectance in a FPI is presented in a comparative study between one FPI design using stoichiometric material (Si3N4) and two designs based on N-rich compositions, SiN1.39 and SiN1.49. Spectral measurements confirm that if the design accounts for phase penetration depth, sufficient performance can be achieved with the SiN1.49-based FPI design for gas absorption spectroscopy in near-UV, with peak transmission at 330 nm of 64%, a free spectral range (FSR) of 20 nm and a full-width half-magnitude spectral resolution (FWHM) of 2 nm.
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Gryga, Michal, Dalibor Ciprian et Petr Hlubina. « Distributed Bragg Reflectors Employed in Sensors and Filters Based on Cavity-Mode Spectral-Domain Resonances ». Sensors 22, no 10 (10 mai 2022) : 3627. http://dx.doi.org/10.3390/s22103627.
Texte intégralRésumé :
Spectral-domain resonances for cavities formed by two distributed Bragg reflectors (DBRs) were analyzed theoretically and experimentally. We model the reflectance and transmittance spectra of the cavity at the normal incidence of light when DBRs are represented by a one-dimensional photonic crystal (1DPhC) comprising six bilayers of TiO2/SiO2 with a termination layer of TiO2. Using a new approach based on the reference reflectance, we model the reflectance ratio as a function of both the cavity thickness and its refractive index (RI) and show that narrow dips within the 1DPhC band gap can easily be resolved. We revealed that the sensitivity and figure of merit (FOM) are as high as 610 nm/RIU and 938 RIU−1, respectively. The transmittance spectra include narrow peaks within the 1DPhC band gap and their amplitude and spacing depend on the cavity’s thickness. We experimentally demonstrated the sensitivity to variations of relative humidity (RH) of moist air and FOM as high as 0.156 nm/%RH and 0.047 %RH−1, respectively. In addition, we show that, due to the transmittance spectra, the DBRs with air cavity can be employed as spectral filters, and this is demonstrated for two LED sources for which their spectra are filtered at wavelengths 680 nm and 780 nm, respectively, to widths as narrow as 2.3 nm. The DBR-based resonators, thus, represent an effective alternative to both sensors and optical filters, with advantages including the normal incidence of light and narrow-spectral-width resonances.
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Gebhardt, Markus, Jeffrey M. DeVries, Jana Jungjohann, Gino Casale, Andreas Gegenfurtner et Jörg-Tobias Kuhn. « Measurement Invariance of a Direct Behavior Rating Multi Item Scale across Occasions ». Social Sciences 8, no 2 (4 février 2019) : 46. http://dx.doi.org/10.3390/socsci8020046.
Texte intégralRésumé :
Direct Behavior Rating (DBR) as a behavioral progress monitoring tool can be designed as longitudinal assessment with only short intervals between measurement points. The reliability of these instruments has been mostly evaluated in observational studies with small samples based on generalizability theory. However, for a standardized use in the pedagogical field, a larger and broader sample is required in order to assess measurement invariance between different participant groups and over time. Therefore, we constructed a DBR, the Questionnaire for Monitoring Behavior in Schools (QMBS) with multiple items to measure the occurrence of specific externalizing and internalizing student classroom behaviors on a Likert scale (1 = never to 7 = always). In a pilot study, two trained raters observed 16 primary education students and rated the student behavior over all items with a satisfactory reliability. In the main study, 108 regular primary school students, 97 regular secondary students, and 14 students in a clinical setting were rated daily over one week (five measurement points). Item response theory (IRT) analyses confirmed the technical adequacy of the instrument and latent growth models demonstrated the instrument’s stability over time. Further development of the instrument and study designs to implement DBRs is discussed.
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Yu, Tai-Cheng, Wei-Ta Huang, Hsiang-Chen Wang, An-Ping Chiu, Chih-Hsiang Kou, Kuo-Bin Hong, Shu-Wei Chang, Chi-Wai Chow et Hao-Chung Kuo. « Design and Simulation of InGaN-Based Red Vertical-Cavity Surface-Emitting Lasers ». Micromachines 15, no 1 (30 décembre 2023) : 87. http://dx.doi.org/10.3390/mi15010087.
Texte intégralRésumé :
We propose a highly polarized vertical-cavity surface-emitting laser (VCSEL) consisting of staggered InGaN multiple quantum wells (MQWs), with the resonance cavity and polarization enabled by a bottom nanoporous (NP) n-GaN distributed Bragg reflectors (DBRs), and top TiO2 high-index contrast gratings (HCGs). Optoelectronic simulations of the 612 nm VCSEL were systematically and numerically investigated. First, we investigated the influences of the NP DBR and HCG geometries on the optical reflectivity. Our results indicate that when there are more than 17 pairs of NP GaN DBRs with 60% air voids, the reflectance can be higher than 99.7%. Furthermore, the zeroth-order reflectivity decreases rapidly when the HCG’s period exceeds 518 nm. The optimal ratios of width-to-period (52.86 ± 1.5%) and height-to-period (35.35 ± 0.14%) were identified. The staggered MQW design also resulted in a relatively small blue shift of 5.44 nm in the emission wavelength under a high driving current. Lastly, we investigated the cavity mode wavelength and optical threshold gain of the VCSEL with a finite size of HCG. A large threshold gain difference of approximately 67.4–74% between the 0th and 1st order transverse modes can be obtained. The simulation results in this work provide a guideline for designing red VCSELs with high brightness and efficiency.
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Ramdany, Ramdany, et Yuni Setiawati. « ANALISIS PENATAUSAHAAN ASET TETAP BARANG MILIK NEGARA (BMN) ». JURNAL AKUNTANSI 10, no 2 (2 décembre 2021) : 310–23. http://dx.doi.org/10.37932/ja.v10i2.345.
Texte intégralRésumé :
Penelitian ini bertujuan untuk mengetahui kesesuaian pelaksanaan penatausahaan Barang Milik Negara (BMN) pada satuan kerja Sekretariat Jenderal Kementerian Perdagangan dengan Peraturan Menteri Keuangan nomor 181/PMK.06/2016 tentang Penatausahaan BMN dan efektifitas aplikasi Sistem Informasi Manajemen Akuntansi Barang Milik Negara (SIMAK BMN). Pendekatan penelitian ini adalah kualitatif deskriptif dengan metode pengumpulan data berupa wawancara, observasi, dan studi pustaka. Hasil penelitian menunjukkan bahwa secara keseluruhan pelaksanaan penatausahaan BMN berupa aset tetap dan efektivitas SIMAK BMN pada satuan kerja Sekretariat Jenderal Kementerian Perdagangan cukup optimal namun perlu ada perbaikan seperti masih ditemukan asset yang belum tercatat dalam Daftar Barang di Ruangan (DBR) dan Daftar Barang di Luar Ruangan (DBL), permasalahan pemutakhiran data asset, penyimpanan dokumen BMN, tindak lanjut inventarisasi asset yang tidak ditemukan, dan masalah sumber daya manusia. Diharapkan kebijakan mengenai penataan BMN selanjutnya memperbaiki temuan penelitian diatas sehingga dapat meningkatkan kualitas informasi laporan keuangan dan akuntabilitas penyelenggaraan entitas public
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J.F. Gurbanova, A.F. Amirova, K.A. Heydarova, A.E. Huseynova et E.Sh. Salimova. « Dölün əsas ultrasəs əlamətləri intrauterin böyümənin məhdudlaşdırılması ». Actual Questions of Modern Gynecology and Perinatology 9, no 3 (27 octobre 2022) : 9–17. http://dx.doi.org/10.28942/mgpam.v9i3.77.
Texte intégralRésumé :
Dölün bətndaxili inkişaf ləngiməsi (DBİL) yayılmış və mürəkkəb mamalıq problemidir. Qeyd edilmişdir ki, DBİL hamilə qadınların təqribən 10-15%-də, yeni doğulmuşların 5-10%-də rast gələrək, perinatal xəstələnmə və ölümün əsas faktorudur [1, 2]. Çox vaxt DBİL ümumi patogenetik inkişaf mexanizmlərinin olması ilə hamiləliyin kəsilməsi ilə əlaqələndirilir [1]. DBİL neonatal və postneonatal dövrlərdə döl ölümün mühüm risk faktorudur. DBİL olan uşaqların ölümü normal inkişaf edən yeni doğulmuş uşaqların ölümündən 3-10 dəfə yüksəkdir [1]. DBİLnin olması ölü doğum riskini 8 dəfə artırır. Ölü doğulan körpələrin təxminən 20%-də DBİL var [3, 4].
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Xu, Xiaoqin, Xin Yang, Xue Liu, Yanghui Bi, Pengzhou Kong, Yanqiang Wang, Xiaolong Cheng et Yanfeng Xi. « The Role of DBR1 as a Candidate Prognosis Biomarker in Esophageal Squamous Cell Carcinoma ». Technology in Cancer Research & ; Treatment 21 (janvier 2022) : 153303382210831. http://dx.doi.org/10.1177/15330338221083105.
Texte intégralRésumé :
Aims: Esophageal squamous cell carcinoma (ESCC) is one of the most prevalent malignancies with unfavorable clinical outcomes and limited therapeutic methods. As a key enzyme in RNA metabolism, debranching RNA Lariats 1 (DBR1) is involved in intron turnover and biogenesis of noncoding RNA. Although cancer cells often show disorder of nucleic acid metabolism, it is unclear whether DBR1 has any effect on the carcinogenesis and progression of ESCC. Methods: Here we detected DBR1 expression in 112 ESCC samples by immunohistochemistry and analyzed its correlation with clinical parameters and survival. Results: DBR1 is mainly located in the nucleus of ESCC tissue. And DBR1 was associated with several malignant clinical features in patients, including tumor location ( χ2 = 9.687, P = .021), pathologic T stage ( χ2 = 5.771, P = .016), lymph node metastasis ( χ2 = 8.215, P = .004) and N classification ( χ2 = 10.066, P = .018). Moreover, Kaplan-Meier analysis showed that ESCC patients harboring lower DBR1 expression had a worse prognosis in comparison with those with higher DBR1 expression ( P = .005). Univariate and multivariate Cox proportional hazards regression analyses indicated that decreased DBR1 might act as an independent predictor of poor prognosis for ESCC patients. Conclusion: Abnormal RNA metabolism might play a critical role in promoting the progression of ESCC, and DBR1 may be a promising potential biomarker for predicting the prognosis of ESCC patients.
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Ihara, H., Y. Aoki, T. Aoki et M. Yoshida. « Light has a greater effect on direct bilirubin measured by the bilirubin oxidase method than by the diazo method ». Clinical Chemistry 36, no 6 (1 juin 1990) : 895–97. http://dx.doi.org/10.1093/clinchem/36.6.895.
Texte intégralRésumé :
Abstract We compared the effect of light on direct-reacting bilirubin (DBIL) measurement by the bilirubin oxidase (EC 1.3.3.5; BOX) method and by the Jendrassik-Gróf diazo method. DBIL concentrations determined by the BOX method in the sera of hyperbilirubinemic infants treated with phototherapy yielded falsely higher values than those by the direct diazo method. A similar tendency was noted when DBIL concentrations in infants' sera irradiated with light in vitro were determined by both methods, although by HPLC none of these sera had detectable DBIL (i.e., conjugated plus delta bilirubin). In general, DBIL concentrations after photoirradiation remained unchanged when measured by the diazo method, but significantly increased when the BOX method was used. Indeed, photoirradiation gave rise to material that acted like a photobilirubin product, which was oxidized at pH 3.7 and therefore was measured as DBIL. Such false increases in DBIL values generated by the BOX method may have clinical diagnostic implications in monitoring jaundiced neonates and in differentiating between physiological jaundice and incipient pathological jaundice.
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Przewoźny, Tomasz, et Jerzy Kuczkowski. « Hearing loss in patients with extracranial complications of chronic otitis media ». Otolaryngologia Polska 71, no 3 (30 juin 2017) : 36–42. http://dx.doi.org/10.5604/01.3001.0010.0130.
Texte intégralRésumé :
Objective: A pure tone audiomety analysis of patients with extracranial complications of chronic suppurative otitis media (ECCSOM). Material and methods: We retrospectively analyzed audiometric data performed before treatment from 63 patients with ECCSOM (56 single, 7 multiple complications) including groups of frequencies. Results: The greatest levels of hearing loss were noted for 6 and 8 kHz (79.0 and 75.7 dBHL) and for the frequency groups high tone average (76.1 dBHL). As regards the severity of hearing impairment in pure tone average the prevalence of complications was as follows: labyrinthitis (77.8±33.6 dBHL), facial palsy (57.1±14.3 dBHL), perilymphatic fistula (53.9±19.9 dBHL) and mastoiditis (42.2±9.5 dBHL) (p=0.023). Conclusions: Hearing loss in ECCSOM is dominated by mixed, high-tone, moderate type of hearing loss, most profound in labyrinthitis. In 11% of patients the complication causes total deafness.
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Al-Qudah, M., et P. J. D. Dawes. « Malleus–stapes assembly : experience with two prostheses ». Journal of Laryngology & ; Otology 120, no 9 (2 juin 2006) : 736–39. http://dx.doi.org/10.1017/s002221510600168x.
Texte intégralRésumé :
Tympanoplasty is often a necessary part of middle-ear surgery, the most common defect being that between an intact, mobile stapes and the malleus handle. The most readily available tissue is the patient's incus, reshaped to bridge the space between an intact stapes and the malleus. When the incus cannot be used, the hydroxyapatite Wehrs incus prosthesis® can be used as an alternative.Twenty-six patients had an autograft incus ossiculoplasty and 20 patients underwent modified Wehrs incus prosthesis ossiculoplasty. The average post-operative air–bone gaps (ABGs) were 16.2 dB hearing loss (dBHL) and 17.2 dBHL, respectively. Air–bone gap closure to within 15 dBHL was achieved for 48 per cent of incus autografts and for 57 per cent of Wehrs prostheses, and to within 20 dBHL for 77 per cent and 62 per cent, respectively. Over four years follow up, the reconstruction was stable for each group, the ABGs being 17.7 dBHL and 17.1 dBHL, respectively.
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Doumas, B. T., B. Perry, B. Jendrzejczak et L. Davis. « Measurement of direct bilirubin by use of bilirubin oxidase. » Clinical Chemistry 33, no 8 (1 août 1987) : 1349–53. http://dx.doi.org/10.1093/clinchem/33.8.1349.
Texte intégralRésumé :
Abstract We developed an enzymatic method for measuring direct-reacting bilirubin (DBIL) in serum. At pH 4.5, bilirubin oxidase (BOX) oxidizes mono-conjugated bilirubin, di-conjugated bilirubin, and most of the delta-bilirubin to biliverdin. The resulting decrease in absorbance at 460 nm is linearly related to the concentration of DBIL in serum. Mean DBIL values in the 51 patients' sera examined by the BOX method and a diazo procedure (Clin Chem 1982;28:2305) were 45.4 and 42.8 mg/L, respectively. For the same samples, mean values for DBIL and conjugated bilirubin by the Kodak "Ektachem" methods were 50.2 and 24.8 mg/L, respectively. Hemoglobin, up to 1.5 g/L, does not interfere. Unconjugated bilirubin reacts negligibly. Day-to-day CVs were 2.2% and 2.4% at DBIL concentrations of 37 and 74 mg/L, respectively.
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Chuang, Ricky Wenkuei, Yu-Hsin Huang et Tsung-Han Tsai. « Germanium-Tin (GeSn) Metal-Semiconductor-Metal (MSM) Near-Infrared Photodetectors ». Micromachines 13, no 10 (14 octobre 2022) : 1733. http://dx.doi.org/10.3390/mi13101733.
Texte intégralRésumé :
Narrow-bandgap germanium–tin (GeSn) is employed to fabricate metal–semiconductor–metal (MSM) near-infrared photodetectors with low-dark currents and high responsivity. To reduce the dark current, the SiO2 layer is inserted in between the metal and semiconductor to increase the barrier height, albeit at the expense of photocurrent reduction. To couple more incident light into the absorption layer to enhance the responsivity, the distributed Bragg reflectors (DBRs) are deposited at the bottom of the GeSn substrate while placing the anti-reflection layer on the surface of the absorption layer. With the interdigital electrode spacing and width, both set at 5 µm and with 1 V bias applied, it is found the responsivities of the generic MSM control sample detector, the MSM with DBR, and the MSM with AR layer are 0.644 A/W, 0.716 A/W, and 1.30 A/W, respectively. The corresponding specific detectivities are 8.77 × 1010, 1.11 × 1011, and 1.77 × 1011 cm·Hz1/2/W, respectively. The measurement data show that these designs effectively enhance the photocurrent and responsivity. At 1 V bias voltage, normalized responsivity evinces that the photodetection range has been extended from 1550 nm to over 2000 nm, covering the entire telecommunication band. Incorporating GeSn as a sensing layer offers one of the new alternative avenues for IR photodetection.
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Białek, Ewelina, Grzegorz Szwachta, Miron Kaliszewski et Małgorzata Norek. « Charge Density-Versus Time-Controlled Pulse Anodization in the Production of PAA-Based DBRs for MIR Spectral Region ». Energies 14, no 16 (20 août 2021) : 5149. http://dx.doi.org/10.3390/en14165149.
Texte intégralRésumé :
A robust and reliable method for fabricating porous anodic alumina (PAA)-based distributed Bragg reflectors (DBRs), operating in mid-infrared (MIR) spectral region, is presented. The method relies on application of high (UH) and low (UL) voltage pulse sequence repeated in cycles. PAA-based DBR consists of alternating high-(dH) and low-porosity (dL) layers translated directly into periodically varied refractive index. Two anodization modes were used: time- and charge density-controlled mode. The former generated dH + dL pairs with non-uniform thickness (∆d) and effective refractive index (∆neff). It is supposed, that owing to a compensation effect between the ∆d and ∆neff, the photonic stopbands (PSBs) were symmetrical and intensive (transmittance close to zero). Under the charge density-controlled mode dH + dL pairs of uniform thickness were formed. However, the remaining ∆neff provided an asymmetrical broadening of PSBs. Furthermore, it is demonstrated that the spectral position of the PSBs can be precisely tuned in the 3500–5500 nm range by changing duration of voltage pulses, the amount of charge passing under subsequent UH and UL pulses, and by pore broadening after the electrochemical synthesis. The material can be considered to be used as one-dimensional transparent photonic crystal heat mirrors for solar thermal applications.
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Deng, Xiaoheng, Shunmeng Yin, Xinjun Pei, Lixin Lin, Xuechen Chen et Jinsong Gui. « E-DBRL : efficient double broad reinforcement learning for adaptive traffic signal control ». Applied Intelligence, 29 juin 2024. http://dx.doi.org/10.1007/s10489-024-05637-1.
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Shi, Lang, Yuechang Sun, Yongjin Cui, Peng Du, Jiaming Zhuang et Shengjun Zhou. « Strategically constructed high-reflectivity multiple-stack distributed Bragg reflectors for efficient GaN-based flip-chip mini-LEDs ». Journal of Physics D : Applied Physics, 27 mars 2023. http://dx.doi.org/10.1088/1361-6463/acc7b3.
Texte intégralRésumé :
Abstract Full-angle distributed Bragg reflectors (DBRs) consisting of numerous sub-DBRs with discrete central wavelengths have been developed to enhance performance of GaN-based flip-chip mini light-emitting diodes (FC mini-LEDs). However, relatively low reflectivity of full-angle DBRs at large angle incidence restricts further enhancement in performance of FC mini-LEDs. Here, we introduce a reflectivity optimization strategy for constructing high-reflectivity multiple-stack DBRs by rationally engineering the number of sub-DBRs and adjusting central wavelength distribution of sub-DBRs. Based on the reflectivity optimization strategy, we devise a Ti3O5/SiO2 quintuple-stack DBR which is composed of five sub-DBRs. Our quintuple-stack DBR maintains a high reflectivity (>97.5%) over a wide range of incident angles of light. Notably, compared with the full-angle DBR, our quintuple-stack DBR exhibits higher reflectivity at large angle incidence and thinner multilayer thickness. Furthermore, we demonstrate two types of GaN-based blue FC mini-LEDs with indium-tin oxide (ITO)/quintuple-stack DBR and ITO/full-angle DBR p-type ohmic contacts. Benefiting from superior reflection performance, blue FC mini-LED with ITO/quintuple-stack DBR achieves an enhancement of ~5.8% in light output power at 10 mA, in comparison with blue FC mini-LED with ITO/full-angle DBR. Our work signifies an advancement towards high-reflectivity DBRs, which enables higher-performance FC mini-LEDs.
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Wang, Xingwen, Lan Wu, Li Xiang, Ranran Gao, Qinggang Yin, Mengyue Wang, Zhaoyu Liu et al. « Promoter Variations in DBR2-Like Affect Artemisinin Production in Different chemotypes of Artemisia annua ». Horticulture Research, 16 août 2023. http://dx.doi.org/10.1093/hr/uhad164.
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Abstract Artemisia annua is the only known plant source of the potent antimalarial artemisinin, which occurs as the low- and high-artemisinin producing (LAP and HAP) chemotypes. Nevertheless, the different mechanisms of artemisinin producing between these two chemotypes were still not fully understood. Here, we performed a comprehensive analysis of genome resequencing, metabolome, and transcriptome data to systematically compared the difference in the LAP chemotype JL and HAP chemotype HAN. Metabolites analysis revealed that 72.18% of sesquiterpenes was highly accumulated in HAN compared to JL. Integrated omics analysis found a DBR2-Like (DBR2L) gene may be involved in artemisinin biosynthesis. DBR2L was highly homologous with DBR2, belonged to ORR3 family, and had the DBR2 activity of catalyzing artemisinic aldehyde to dihydroartemisinic aldehyde. Genome resequencing and promoter cloning revealed that complicated variations existed in DBR2L promoters among different varieties of A. annua, and were clustered into three variation types. The promoter activity of diverse variant types showed obvious differences. Furthermore, the core region (-625 to 0) of the DBR2L promoter was identified and candidate transcription factors involved in DBR2L regulation were screened. Thus, the result indicates that DBR2L is another key enzyme involved in artemisinin biosynthesis. The promoter variation in DBR2L affects its expression level, thereby may result in the different yield of artemisinin in varieties of A. annua. It provides a novel insight into the mechanism of artemisinin-producing difference in LAP and HAP chemotypes of A. annua, and will assist in a high yield of artemisinin in A. annua.
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Sun, Yuechang, Lang Shi, Yongjin Cui, Bin Tang, Qianxi Zhou, Jiaming Zhuang et Shengjun Zhou. « Effect of distributed Bragg reflectors on optoelectronic characteristics of GaN-based flip-chip light-emitting diodes ». Semiconductor Science and Technology, 20 mai 2024. http://dx.doi.org/10.1088/1361-6641/ad4dd8.
Texte intégralRésumé :
Abstract Distributed Bragg reflectors have been widely utilized in GaN-based flip-chip light-emitting diodes (FCLEDs) owing to their excellent reflection performance. Recently, wide reflected angle DBR (WRA-DBR) has been suggested to enhance the optical characteristics of GaN-based FCLEDs by incorporating multiple sub-DBRs with varying central wavelengths. However, the reflectivity of WRA-DBR decreases at large incident angle from 425 nm to 550 nm, which restricts further optical performance improvement of FCLEDs. Here, we demonstrate a quintuple-stack DBR comprised of five sub-DBRs. The quintuple-stack DBR possesses a high reflectivity (>97.5%) for incident angles below 50° within the blue and green light wavelength ranges. Compared to WRA-DBR, quintuple-stack DBR exhibits a higher reflectivity in wavelength range of 425 nm to 550 nm and thinner multilayer thicknesses. Furthermore, stronger electric field intensities exist in the top facet and sidewalls of FCLED with quintuple-stack DBR, revealing that quintuple-stack DBR is beneficial for enhancing the light extraction efficiency. As a result, the light output power of FCLED with quintuple-stack DBR is ~3% higher than that of FCLED with WRA-DBR at 750 mA.
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Wilson, Debra Paige, et Ray R. LaPierre. « Corrugated nanowires as distributed Bragg reflectors ». Nano Express, 26 août 2022. http://dx.doi.org/10.1088/2632-959x/ac8d1f.
Texte intégralRésumé :
Abstract Distributed Bragg reflectors (DBRs), comprised of periodic refractive index changes, are widely used in optoelectronic devices as resonators, filters and sensors. The heterostructures required for DBRs can be difficult to implement in nanostructures due to poor compositional control on the nanoscale. In the present paper, simulation results are presented of the reflectance spectra from DBR structures that are implemented using periodic perturbations of a nanowire (NW) diameter, rather than heterostructures. The corrugated NW structure can produce a DBR stopband with reflectance near unity. The Bragg wavelength and stopband can be tuned by adjusting the pitch of the nanowire arrays, the corrugation depth, and the period of the corrugation. The proposed DBR structure presents a new paradigm for a wide range of nanoscale device applications.
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Zekri, Jamal, Azhar Nawaz, Haleem Rasool, Imran Ahmad, Hossam Abdel Rahman, Reyad Dada, Ehab Mosaad Abdelghany et al. « Impact of granulocyte-colony stimulating factor on docetaxel-induced febrile neutropenia in patients with breast cancer ». Journal of Oncology Pharmacy Practice, 3 août 2021, 107815522110309. http://dx.doi.org/10.1177/10781552211030974.
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Background Febrile neutropenia (FN) is a life-threatening complication of Docetaxel-based chemotherapy regimens (DBRs). Prophylactic granulocyte-colony stimulating factor (G-CSF) can reduce the risk of FN. This study investigated the effect of G-CSF on FN in patients receiving DBRs for breast cancer. Methods Patients treated between 2015 and 2017 were identified from the hospital’s pharmacy database and their medical records were examined retrospectively. Data from patients’ first four cycles of DBR were collected. FN rate, FN associated length of hospital stay (FN-LOS), and chemotherapy dose modification/delay due to FN were compared between patients who did (G-CSF group) or did not (non-GCSF group) receive prophylactic G-CSF. Results Of the 276 included patients, 83.3% received a DBR as adjuvant or neoadjuvant therapy, and 50% received docetaxel as combination therapy. Prophylactic G-CSF was administered with the first cycle of a DBR in 69.9% of patients who were significantly less likely to experience FN compared to the non-G-CSF group (6.2% vs. 15.7%; odds ratio: 0.36 [95% CI: 0.16–0.82]; p = 0.020). Collectively and after the 4 DBR treatment cycles, FN rate (4.8 vs. 8.5; odds ratio: 0.54 [95% CI: 0.30–0.97]; p = 0.043) and the mean FN-LOS (3.55 vs. 5.28 days; t = –2.22; p = 0.037) were reduced in the G-CSF group. There was no difference in DBR dose delay/reduction between both groups in cycles 2–4. Conclusion In patients receiving DBRs for breast cancer, prophylactic G-CSF significantly reduced both the rate of FN and duration of hospitalization for FN.
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Baghdasaryan, H. V., T. M. Knyazyan, T. H. Baghdasaryan, B. Witzigmann et F. Roemer. « Absorption loss influence on optical characteristics of multilayer distributed Bragg reflector : wavelength-scale analysis by the method of single expression ». Opto-Electronics Review 18, no 4 (1 janvier 2010). http://dx.doi.org/10.2478/s11772-010-0049-0.
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AbstractElectrodynamical model of a classical distributed Bragg reflector (DBR) consisting of alternating quarter-wave layers of high and low permittivity is considered at the plane wave normal incidence. Reflective characteristics of DBR possessing absorption loss in constituting layers are analysed via correct wavelength-scale boundary problem solution by the method of single expression (MSE). Analysis of optical field and power flow density distributions within the lossy DBR structures explained the peculiarities of their reflective characteristics. Optimal configurations of lossless and lossy DBRs are revealed. Specific DBR structures possessing full transparency at definite number of layers are also analysed.
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Zhang, Chichang, et Aris Christou. « Design and Fabrication of a VCSEL With Graded Bragg Mirror Interfaces for Operation at 850nm ». MRS Proceedings 744 (2002). http://dx.doi.org/10.1557/proc-744-m5.44.
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ABSTRACTBased on the AlxGa1-xAs/GaAs system and with graded Distributed Bragg mirrors (DBRs), a VCSEL for operation at 850–860nm is reported. The graded transition bands inside the DBRs were designed in order to achieve the tradeoff between the number of DBR layers and the low threshold current of the laser. The structure optimized had 39 pairs in the n-DBR stack and a low threshold current of 1.6mA was achieved. The device was fabricated with MBE growth, oxide confinement and RIE for MESA definition. The experimental results and physical characterization of the device are also reported to fully understand the VCSEL performance. The threshold current and other parameters predicted by the simulation are in good agreement with experimental results.
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Yamada, Hisashi, Naoto Kumagai et Toshikazu Yamada. « Metal–Organic Chemical Vapor Deposition of n‐AlGaN Grown on Strain‐Relaxed Distributed Bragg Reflector Buffer Layers ». physica status solidi (b), 22 avril 2024. http://dx.doi.org/10.1002/pssb.202300558.
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The strain relaxation, surface morphology, and reflectivity of AlGaN‐distributed Bragg reflectors (DBRs) grown via metal–organic chemical vapor deposition on AlN/Al2O3 templates are investigated. Strain relaxation begins in a 10‐period Al0.50Ga0.50N (27 nm)/Al0.75Ga0.25N (29 nm) DBR, and the degree of strain relaxation (DSR) increases with the number of DBR periods. The 30‐period DBR exhibits a peak reflectivity of 0.82 at 279 nm, with a stopband of 12 nm. The DSR of n‐Al0.62Ga0.38N on the 30‐period DBR increases from 70% to 100% as the n‐Al0.62Ga0.38N thickness increases from 0.4 to 2.5 μm. Although the surface of a DBR comprises numerous spiral hillocks, n‐Al0.62Ga0.38N grown on an AlGaN DBR exhibits a step‐flow growth. A DSR of 100% with threading screw dislocations of 2.0 × 108 cm−2 and threading edge dislocations of 1.2 × 109 cm−2 is obtained for a 2.5 μm‐thick n‐Al0.62Ga0.38N on a 30‐period AlGaN DBR.
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Kobayashi, Kenta, Taichi Nishikawa, Ruka Watanabe, Tetsuya Takeuchi, Satoshi Kamiyama, Motoaki Iwaya et Toshihiro Kamei. « In Situ Center Wavelength Control of AlInN/GaN Distributed Bragg Reflectors with In Situ Reflectivity Spectra Measurements ». physica status solidi (b), 25 mars 2024. http://dx.doi.org/10.1002/pssb.202400010.
Texte intégralRésumé :
An in situ control of a center wavelength in a 40‐pair AlInN/GaN distributed Bragg reflector (DBR) for GaN‐based vertical‐cavity surface‐emitting lasers (VCSELs) with an in situ reflectivity spectra measurement is proposed and developed. A procedure of the in situ control consists of the following three steps: 1) to grow an initial 5‐pair DBR; 2) to obtain the center wavelength value just after the initial DBR growth by the in situ reflectivity spectra measurement; and 3) to adjust growth times as a result of the obtained center wavelength value and continue the remaining 35‐pair DBR. It is experimentally demonstrated that the in situ control of the center wavelength in the 40‐pair DBRs with the ±2% thickness deviations in the initial 5‐pair DBR results in reductions of the deviation down to ±0.3%. The in situ DBR center wavelength control is a key technique for highly reproducible GaN‐based VCSELs.