Articles de revues : « Zero mode Laser »

1

Yan, Qin, Jian Lu et Xiao Wu Ni. « Measurement of the Transient Velocity of Nanoparticles in Flowing Nanofluids by Using the Method of Dynamic Laser Speckles ». Applied Mechanics and Materials 226-228 (novembre 2012) : 1852–57. http://dx.doi.org/10.4028/www.scientific.net/amm.226-228.1852.

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Experimental equipments are designed for the zero-crossing method of dynamic laser speckles to investigate the moving nature of nanoparticles in flowing nanofluids. After the experiments the velocity of nanoparticles in flowing nanofluids is determined according to its relationship with the zero-crossing rate of speckle intensity fluctuation. The results show that the zero-crossing rate is very sensitive to the velocity of nanoparticles when the velocity of nanofluids ranges from 17.6 mm/s to 60.2 mm/s. A TEM10 mode–like laser beam is designed and taken as an incident light to detect the moving direction of nanoparticles in flowing nanofluids. The moving direction of nanoparticles is parallel to the horizontal axis of the TEM10 mode-like laser beam when the zero-crossing rate reaches maximum. Experimental results show that the moving direction of nanoparticles can also be detected by using the zero-crossing method.

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Kolbas, Yu Yu, et M. A. Ivanov. « Improved Algorithm for Mathematical Correction of the Zero Drift of the Zeeman Laser Gyro with Switching Longitudinal Mode of Generation ». Herald of the Bauman Moscow State Technical University. Series Instrument Engineering, n^o 2 (125) (avril 2019) : 91–103. http://dx.doi.org/10.18698/0236-3933-2019-2-91-103.

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The paper addresses time and temperature zero drifts in Zeeman laser gyroscope (RLG) operating in the mode of periodic adjustment of RLG to the longitudinal mode of generation with the opposite circular polarization of the light wave. In such a gyroscope, the zero drift can be divided into magnetic and non-magnetic components having different nature and making a significantly different contribution to the final error. Algorithmic methods are proposed for mathematical compensation of RLG zero drift, both with and without using initial calibration. It is shown that the simultaneous use of reproducible dependencies of the magnetic and non-magnetic zero drifts due to RLG temperature changes allows solving the problem of RLG zero drift correction in the optimal way. The correction factors are calculated from the temperature of a Zeeman laser gyro at the moment of activation. At the same time, using the difference between the temperatures of the gyroscope and gyro case, where it is installed, it is possible to determine the temperature of the Zeeman laser gyroscope at the moment of switching on, thereby eliminating the problem of calculating the correction factors when the gyroscope is turned off and then on again. Experimental results for several Zeeman laser gyroscopes with typical values of zero drifts are presented

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Zakharyash, V. F., V. M. Klement’ev et E. A. Titov. « Forced mode locking in a semiconductor laser ». Journal of Physics : Conference Series 2067, n^o 1 (1 novembre 2021) : 012005. http://dx.doi.org/10.1088/1742-6596/2067/1/012005.

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Abstract A brief description of the theory of mode locking of a semiconductor laser when the modulating generator frequency is close to the intermode frequency is given. It is shown that during mode locking there is phase locking, due to which the dispersion of summed intensity in the interpulse interval tends to zero.

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Bourcier, Roy J. « Near-Zero Shift Attachment for Optoelectronic Components ». International Symposium on Microelectronics 2011, n^o 1 (1 janvier 2011) : 001058–66. http://dx.doi.org/10.4071/isom-2011-tha5-paper3.

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High performance laser-based optoelectronic devices commonly feature the use of free-space optical coupling between the laser diode and optical elements such as filters, secondary harmonic generators and optical fibers. A critical challenge in the assembly of such components is maintaining the required optical alignment precision during attachment of the optical subcomponents to a common platform. In the case of devices based on single mode waveguides, the post-attach shift must often be held to less than a few hundred nanometers to achieve the desired optical coupling efficiency. Historically, these tight tolerances have required the use of costly post-work operations such as laser hammering or re-bend to achieve performance objectives. Over the course of designing several such optoelectronic components, we have used and developed a variety of design concepts and assembly processes which have allowed us to achieve these demanding tolerances, often without the use of post-work. UV-curable structural adhesives and Nd:YAG laser spot welding have been used, individually and in combination, to perform the required sub-micron optomechanical attachments. Several approaches which have been successfully used will be described and their relative merits will be compared. In addition, key design and process elements which can impact post-attach shift will be discussed.

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Clorennec, Dominique, Claire Prada, Daniel Royer et Todd W. Murray. « Laser impulse generation and interferometer detection of zero group velocity Lamb mode resonance ». Applied Physics Letters 89, n^o 2 (10 juillet 2006) : 024101. http://dx.doi.org/10.1063/1.2220010.

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Lee, Seung Seok, et Sang Whoe Dho. « Suppressing Technique of the Antisymmetric Mode by the Superposition of Lamb Waves Generated by Two Laser Beams in a Thin Plate ». Key Engineering Materials 321-323 (octobre 2006) : 103–7. http://dx.doi.org/10.4028/www.scientific.net/kem.321-323.103.

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We present a suppressing technique of the antisymmetric mode by superposition of Lamb waves generated by two laser beams in a thin plate. Two Lamb waves of the same frequency propagating from the opposite direction simultaneously arrive at the point of measurement and are superposed to compose one Lamb wave. The amplitude of the superposed Lamb wave depends on the distance between two laser beams. The suppressing of antisymmetric Lamb wave mode is accomplished by selecting the distance between two beams which simultaneously satisfies the condition of the anti-node(maximum) for the symmetric mode and the minimum for the antisymmetric mode. By this method, the antisymmetric Lamb wave mode is suppressed to the degree of 1.4% of the amplitude measured at zero distance between two beams.

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Cattarusa, Douglas Alan, Xiao Min Jin, Xing Xing Fu, Xiang Ning Kang, Bei Zhang et Guo Yi Zhang. « Optical-Mode Study of Galium Nitrate Based Laser Diodes ». Advanced Materials Research 571 (septembre 2012) : 476–81. http://dx.doi.org/10.4028/www.scientific.net/amr.571.476.

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This paper focuses on the optical mode analysis of laser diodes to improve light emission. Under the mode analysis, we compare the optical confinement factor (OCF) percentage of the emitting light from the LDs. There are two structures which we analyze: a basic GaN waveguide structure and an InGaN waveguide structure. The second structure has additional InGaN waveguides and is analyzed under two additional design variations: the concentration of Indium and the thickness of the top waveguide layer. The results of this study indicate introducing InGaN waveguide layers correlates with lower order modes (zero and first order) and increase the OCF values. The top InGaN waveguide layer, which has a higher concentration of Indium, appears to increase the OCF. However, the increased thickness of the InGaN layer causes the lower modes’ OFC to decrease. Over all, in the best case, InGaN LD has an OCF of 1.8896%, which is about a 312% improvement compared to that of GaN LD ( OCF=0.4535%).

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Hoare, R., R. Mardling et GJ Troup. « Intensity Correlation Functions for 'Thermalised' TEMn0 Laser Beams ». Australian Journal of Physics 39, n^o 4 (1986) : 505. http://dx.doi.org/10.1071/ph860505.

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A well-stabilised, single mode laser beam will give zero intensity correlation. However, a laser beam may be 'thermalised' by shining it on a rotating ground glass disc, and then intensity correlation experiments will give nonzero results. We present here calculations of the intensity correlation functions of the TEMlO, TEM20, TEM30 and TEM40 Gaussian-Hermite beams. We were led to perform these calculations by the results of intensity correlation measurements on a laser with 'butted-on' mirrors nearing the end of its useful life.

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Debnath, Pulak Chandra, et Dong-Il Yeom. « Ultrafast Fiber Lasers with Low-Dimensional Saturable Absorbers : Status and Prospects ». Sensors 21, n^o 11 (25 mai 2021) : 3676. http://dx.doi.org/10.3390/s21113676.

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Wide-spectral saturable absorption (SA) in low-dimensional (LD) nanomaterials such as zero-, one-, and two-dimensional materials has been proven experimentally with outstanding results, including low saturation intensity, deep modulation depth, and fast carrier recovery time. LD nanomaterials can therefore be used as SAs for mode-locking or Q-switching to generate ultrafast fiber laser pulses with a high repetition rate and short duration in the visible, near-infrared, and mid-infrared wavelength regions. Here, we review the recent development of emerging LD nanomaterials as SAs for ultrafast mode-locked fiber laser applications in different dispersion regimes such as anomalous and normal dispersion regimes of the laser cavity operating in the near-infrared region, especially at ~1550 nm. The preparation methods, nonlinear optical properties of LD SAs, and various integration schemes for incorporating LD SAs into fiber laser systems are introduced. In addition to these, externally (electrically or optically) controlled pulsed fiber laser behavior and other characteristics of various LD SAs are summarized. Finally, the perspectives and challenges facing LD SA-based mode-locked ultrafast fiber lasers are highlighted.

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Harb, MS, et FG Yuan. « Barely visible impact damage imaging using non-contact air-coupled transducer/laser Doppler vibrometer system ». Structural Health Monitoring 16, n^o 6 (28 novembre 2016) : 663–73. http://dx.doi.org/10.1177/1475921716678921.

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The aim of this study is to investigate the capability of the zero-lag cross-correlation imaging condition of an A0 Lamb wave mode in imaging a barely visible impact damage in a carbon fiber–reinforced polymer composite using a fully non-contact-guided wave-based non-destructive inspection system. A 16-ply (45/0/-45/90)2s carbon fiber–reinforced polymer laminate was impacted at three different locations with different impact energies using a drop ball at three drop heights causing three barely visible impact damages with different sizes. The A0 Lamb wave mode is generated inside the laminate using a circular air-coupled transducer and detected along the damaged region using a laser Doppler vibrometer. The measured wavefield is then decomposed into a forward and backward propagating wavefields by applying a frequency–wavenumber filtering post-processing technique. The decomposed wavefields are then cross-correlated in the frequency domain using zero-lag cross-correlation imaging condition producing a detailed cumulative damage image. The images obtained in frequency domain highlight the three damaged areas with higher zero-lag cross-correlation values compared to other parts of the inspected areas. The experimental investigation has shown a good correlation between the zero-lag cross-correlation imaging condition and C-scan images, which demonstrate a strong capability of guided wave zero-lag cross-correlation imaging condition technique in approximating the location and size of relatively small barely visible impact damages in thin composite structures.

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Sun, Xiaoli, Daniel R. Cremons, Erwan Mazarico, Guangning Yang, James B. Abshire, David E. Smith, Maria T. Zuber et al. « Small All-Range Lidar for Asteroid and Comet Core Missions ». Sensors 21, n^o 9 (28 avril 2021) : 3081. http://dx.doi.org/10.3390/s21093081.

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We report the development of a new type of space lidar specifically designed for missions to small planetary bodies for both topographic mapping and support of sample collection or landing. The instrument is designed to have a wide dynamic range with several operation modes for different mission phases. The laser transmitter consists of a fiber laser that is intensity modulated with a return-to-zero pseudo-noise (RZPN) code. The receiver detects the coded pulse-train by correlating the detected signal with the RZPN kernel. Unlike regular pseudo noise (PN) lidars, the RZPN kernel is set to zero outside laser firing windows, which removes most of the background noise over the receiver integration time. This technique enables the use of low peak-power but high pulse-rate lasers, such as fiber lasers, for long-distance ranging without aliasing. The laser power and the internal gain of the detector can both be adjusted to give a wide measurement dynamic range. The laser modulation code pattern can also be reconfigured in orbit to optimize measurements to different measurement environments. The receiver uses a multi-pixel linear mode photon-counting HgCdTe avalanche photodiode (APD) array with near quantum limited sensitivity at near to mid infrared wavelengths where many fiber lasers and diode lasers operate. The instrument is modular and versatile and can be built mostly with components developed by the optical communication industry.

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Cao, Yulong, Lei Gao, Yujia Li, Hongqing Ran, Lingdi Kong, Qiang Wu, Ligang Huang, Wei Huang et Tao Zhu. « Polarization-dependent pulse dynamics of mode-locked fiber laser with near-zero net dispersion ». Applied Physics Express 12, n^o 11 (10 octobre 2019) : 112001. http://dx.doi.org/10.7567/1882-0786/ab492d.

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Prada, Claire, Dominique Clorennec, Daniel Royer, Oluwaseyi Balogun et Todd W. Murray. « Laser generation and detection of zero‐group velocity Lamb mode resonance in thin plates ». Journal of the Acoustical Society of America 119, n^o 5 (mai 2006) : 3285. http://dx.doi.org/10.1121/1.4786194.

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de Sousa, Fabio Barros, Simone Cristina da Costa Tavares, Jorge Everaldo de Oliveira, Jackson Moreira Oliveira, Elizabeth Rego Sabino, Lelis Araujo de Oliveira, Alan dos Reis Silva et al. « OPTIMIZATION AND PERFORMANCE ANALYSIS OF DISPERSION COMPENSATION IN RZ AND NRZ SYSTEMS WITH TRANSMISSION RATES OF 10 GBPS AND 40 GBPS ». Brazilian Journal of Development 7, n^o 12 (1 décembre 2021) : 120075–88. http://dx.doi.org/10.34117/bjdv7n12-665.

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Neste trabalho, investigamos um método de compensação de dispersão para as taxas de transmissão de 10 Gbps e 40 Gbps com formatos de modulação retorno ao zero (return to zero - RZ) e não retorno ao zero (non-return to zero - NRZ) usando fibra monomodo (single mode-fiber - SMF) e fibra compensadora de dispersão (dispersion compensating fiber - DCF). A influência da dispersão do compensador DCF com o aumento da potência do laser CW foi estudada, afim de se avaliar o desempenho dos sistemas de comunicação por fibra óptica aqui propostos. Os resultados da simulação foram validados através do formato do pulso, do espectro óptico e do diagrama de olho para a análise do fator Q e da taxa de erro de bit (bit error rate – BER).

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Song, Y. J., M. L. Hu, C. L. Gu, L. Chai, C. Y. Wang et A. M. Zheltikov. « Mode-locked Yb-doped large-mode-area photonic crystal fiber laser operating in the vicinity of zero cavity dispersion ». Laser Physics Letters 7, n^o 3 (mars 2010) : 230–35. http://dx.doi.org/10.1002/lapl.200910135.

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Arkhipov, M. V., A. A. Shimko, R. M. Arkhipov, I. Babushkin, A. A. Kalinichev, A. Demircan, U. Morgner et N. N. Rosanov. « Mode-locking based on zero-area pulse formation in a laser with a coherent absorber ». Laser Physics Letters 15, n^o 7 (5 juin 2018) : 075003. http://dx.doi.org/10.1088/1612-202x/aac1a0.

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Guo, Quanxin, Jie Pan, Dengwang Li, Yiming Shen, Xile Han, Jinjuan Gao, Baoyuan Man, Huanian Zhang et Shouzhen Jiang. « Versatile Mode-Locked Operations in an Er-Doped Fiber Laser with a Film-Type Indium Tin Oxide Saturable Absorber ». Nanomaterials 9, n^o 5 (5 mai 2019) : 701. http://dx.doi.org/10.3390/nano9050701.

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We demonstrate the generation of versatile mode-locked operations in an Er-doped fiber laser with an indium tin oxide (ITO) saturable absorber (SA). As an epsilon-near-zero material, ITO has been only used to fashion a mode-locked fiber laser as an ITO nanoparticle-polyvinyl alcohol SA. However, this type of SA cannot work at high power or ensure that the SA materials can be transmitted by the light. Thus, we covered the end face of a fiber with a uniform ITO film using the radio frequency magnetron sputtering technology to fabricate a novel ITO SA. Using this new type of SA, single-wavelength pulses, dual-wavelength pulses, and triple-wavelength multi-pulses were achieved easily. The pulse durations of these mode-locked operations were 1.67, 6.91, and 1 ns, respectively. At the dual-wavelength mode-locked state, the fiber laser could achieve an output power of 2.91 mW and a pulse energy of 1.48 nJ. This study reveals that such a proposed film-type ITO SA has excellent nonlinear absorption properties, which can promote the application of ITO film for ultrafast photonics.

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Yang, Chun Yan, Yun Hao, Bozhe Wang, Hai Yuan et Liu Hui Li. « Effect of Laser Processing Parameters on Microhole Quality of Aluminium Nitride Ceramics ». Key Engineering Materials 871 (janvier 2021) : 277–83. http://dx.doi.org/10.4028/www.scientific.net/kem.871.277.

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A picosecond laser in spin-cutting mode was used to drill 500μm diameter microholes on 150μm thick aluminium nitride ceramic. The effects of laser processing parameters such as the laser power, scanning speed, and defocus amount on the microhole quality were studied. The results show that as the laser power increases, the inlet and outlet diameters of the holes increase, the taper decreases slightly, and the thickness of the recast layer decreases evidently. The scanning speed has no obvious effect on the diameter and taper of the hole; however, the hole can not be drilled through when the speed is too large. Positive defocus can effectively reduce the taper of the hole. Under 28.5W laser power, 400Hz frequency, 200mm/s scanning speed, and zero defocus amount conditions, high-quality microholes with a taper of 0.85° were obtained.

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Zhang, Yunshan, Yifan Xu, Shijian Guan, Jilin Zheng, Hongming Gu, Lianyan Li, Rulei Xiao, Tao Fang, Hui Zou et Xiangfei Chen. « Modulation bandwidth enhancement in monolithic integrated two-section DFB lasers based on the detuned loading effect ». Journal of Semiconductors 44, n^o 11 (1 novembre 2023) : 112301. http://dx.doi.org/10.1088/1674-4926/44/11/112301.

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Abstract Modulation bandwidth enhancement in a directly modulated two-section distributed feedback (TS-DFB) laser based on a detuned loading effect is investigated and experimentally demonstrated. The results show that the 3-dB bandwidth of the TS-DFB laser is increased to 17.6 GHz and that chirp parameter can be reduced to 2.24. Compared to the absence of a detuned loading effect, there is a 4.6 GHz increase and a 2.45 reduction, respectively. After transmitting a 10 Gb/s non-return-to-zero (NRZ) signal through a 5-km fiber, the modulation eye diagram still achieves a large opening. Eight-channel laser arrays with precise wavelength spacing are fabricated. Each TS-DFB laser in the array has side mode suppression ratios (SMSR) > 49.093 dB and the maximum wavelength residual < 0.316 nm.

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Zeng, Huangjun, Wenze Xue, Robert T. Murray, Weidong Chen, Zhongben Pan, Li Wang, Chen Cui et al. « Continuous-Wave and Mode-Locked Operation of an In-Band Pumped Tm,Ho,Lu:CaGdAlO4 Laser ». Applied Sciences 13, n^o 23 (3 décembre 2023) : 12927. http://dx.doi.org/10.3390/app132312927.

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We investigate in-band pumping of a Tm,Ho,Lu:CaGdAlO4 laser using a Raman-shifted Er-fiber laser (1678 nm), in the continuous-wave (CW) and mode-locked (ML) regimes. A maximum output power of 524 mW is obtained in the CW regime with a 5% output coupler at an absorbed pump power of 2.04 W, corresponding to a slope efficiency of 27.9%. A maximum CW wavelength tuning range of 160 nm at the zero level, from 1984 to 2144 nm, is obtained with a 0.2% output coupler. In the ML regime, pumping with 5.5 W (unpolarized), the average output power (0.2% output coupler) reaches 148 mW at a repetition rate of ~96 MHz. The output spectrum is centered at 2071.5 nm with a FWHM of 21.5 nm (σ-polarization). The pulse duration amounts to 218 fs (time-bandwidth product equal to 0.327).

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Shi, Yin, David R Blackman et Alexey Arefiev. « Electron acceleration using twisted laser wavefronts ». Plasma Physics and Controlled Fusion 63, n^o 12 (15 novembre 2021) : 125032. http://dx.doi.org/10.1088/1361-6587/ac318d.

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Abstract Using plasma mirror injection we demonstrate, both analytically and numerically, that a circularly polarized helical laser pulse can accelerate highly collimated dense bunches of electrons to several hundred MeV using currently available laser systems. The circular-polarized helical (Laguerre–Gaussian) beam has a unique field structure where the transverse fields have helix-like wave-fronts which tend to zero on-axis where, at focus, there are large on-axis longitudinal magnetic and electric fields. The acceleration of electrons by this type of laser pulse is analyzed as a function of radial mode number and it is shown that the radial mode number has a profound effect on electron acceleration close to the laser axis. Using three-dimensional particle-in-cell simulations a circular-polarized helical laser beam with power of 0.6 PW is shown to produce several dense attosecond bunches. The bunch nearest the peak of the laser envelope has an energy of 0.47 GeV with spread as narrow as 10%, a charge of 26 pC with duration of ∼ 400 as, and a very low divergence of 20 mrad. The confinement by longitudinal magnetic fields in the near-axis region allows the longitudinal electric fields to accelerate the electrons over a long period after the initial reflection. Both the longitudinal E and B fields are shown to be essential for electron acceleration in this scheme. This opens up new paths toward attosecond electron beams, or attosecond radiation, at many laser facilities around the world.

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Tai Hyun Yoon, Seong Tae Park, Eok Bong Kim et Jin Yong Yeom. « Orthogonal control of femtosecond mode-locked laser having zero carrier-offset frequency with three-axis PZT ». IEEE Journal of Selected Topics in Quantum Electronics 9, n^o 4 (juillet 2003) : 1025–29. http://dx.doi.org/10.1109/jstqe.2003.819112.

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Cai, Huanfu, Hong Zhang et Yuankai Zheng. « Soft Magnetic Devices Applied for Low Zero Excursion (0.01$^{\circ}$/h) Four-Mode Ring Laser Gyro ». IEEE Transactions on Magnetics 43, n^o 6 (juin 2007) : 2686–88. http://dx.doi.org/10.1109/tmag.2007.893315.

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Wu, Wan Duo, Qiang Xian Huang, Chao Qun Wang, Ting Ting Wu et Hong Xie. « The Analysis and Design of a Large Stroke with High-Precision Polarized Laser Interferometer System ». Key Engineering Materials 679 (février 2016) : 129–34. http://dx.doi.org/10.4028/www.scientific.net/kem.679.129.

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The technique utilizing single-frequency laser interferometry has very high measurement accuracy, but it has rigorous requirements for optical design which is affected by many factors. In order to achieve single-frequency laser interferometry with large stroke and high precision, the integral layout, the polarization phase shifting technique and the common mode rejection method are adopted to design the length interferometry system. This paper analyzes factors and design requirements which affect measurement accuracy with large stroke. Based on polarization phase shifting technique, the system employs the four-beam-signal detection technique and the common mode rejection method, to make a differential processing of four mutually orthogonal signals. Thus, the influences of zero-drift of intensity and environmental change on system are reduced. Combined with a 200 phase subdivision, the system achieves the resolution with 0.8 nm. Under the VC++ environment, the displacement measurement results are compensated and corrected according to the environmental parameters. Compared with the Renishaw XL-80 laser interferometer, the system has better stability in short term. In the measuring range of 60 mm, the effectiveness of the system is verified.

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Hao, Qianqian, Cong Wang, Wenxin Liu, Xiaoqin Liu, Jie Liu et Han Zhang. « Low-dimensional saturable absorbers for ultrafast photonics in solid-state bulk lasers : status and prospects ». Nanophotonics 9, n^o 9 (12 février 2020) : 2603–39. http://dx.doi.org/10.1515/nanoph-2019-0544.

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AbstractLow-dimensional (LD) materials have originated a range of innovative applications in photonics and optoelectronics owning to their advantages of ultrafast carrier response and distinct nonlinear saturable absorption properties. In particular, these emerging LD materials including zero-, one-, and two-dimensional materials have recently been utilized for short and ultrashort pulse laser generation in the visible, near infrared, and mid-infrared wavelength regions. Here, we review recent progress demonstrating the application of LD materials as versatile, wideband saturable absorbers for Q-switching and mode-locking in all-solid-state lasers. The laser performance in operating wavelength, output power, pulse width, repetition rate, and pulse energy is reviewed. Finally, the challenges and future perspectives are suggested.

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Zhang, Jianqiang, Yongkai Liu, Shijie Gao et Chengshan Han. « Control Technology of Ground-Based Laser Communication Servo Turntable via a Novel Digital Sliding Mode Controller ». Applied Sciences 9, n^o 19 (27 septembre 2019) : 4051. http://dx.doi.org/10.3390/app9194051.

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In this study, a sliding mode control (SMC) algorithm was proposed based on a novel reaching law to solve the nonlinear disturbance problem of a ground-based laser communication turntable. This algorithm is a chatter-free method, in which the coefficient of sliding mode variable structure function is designed as an adaptive function, so the chattering of the sliding mode approaches zero. For any perturbed system, this algorithm can ensure a finite time for the system state to reach the sliding mode surface from any initial state. Additionally, the system will stabilize in the quasi-sliding mode domain (QSMD) with O(T3) width, where a narrower QSMD width corresponds to stronger robustness toward nonlinear disturbances. Both mathematical calculations and simulations verified the sliding mode and stability of this control algorithm. Experimental results of the velocity closed-loop of pitch axis show that the proposed algorithm effectively improved the anti-nonlinear disturbance ability of the control system compared with the effects of the traditional digital PID and the existing chatter-reduced SMC algorithms, for smooth system operation.

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Художиткова, Дарья Алексеевна. « Optimization of a mode-locked fiber laser based on nonlinear polarization rotation using genetic algorithm ». Вычислительные технологии, n^o 4(25) (16 septembre 2020) : 20–30. http://dx.doi.org/10.25743/ict.2020.25.4.003.

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Выполнено математическое моделирование волоконного лазера с синхронизацией мод на основе эффекта нелинейного вращения поляризации. Проведена оптимизация лазера с использованием генетического алгоритма. В результате были определены параметры лазерного резонатора, при которых достигается наибольшая энергия выходного импульса Purpose. The article addresses optimization of mode-locked fiber laser based on nonlinear polarization rotation. Determination of the resonator parameters corresponding to the single-pulse with the highest energy has been performed using the genetic algorithm. Metodology. Mathematical modelling has been carried out with the help of two models, namely, scalar and hybrid. Scalar model describes signal propagation by generalized nonlinear Schr¨odinger equation. Hybrid model describes section of DCF by pair of generalized nonlinear Schrodinger equations. Numerical simulation has been performed by the split-step Fourier method. Genetic algorithm has been implemented as SteadyState method by GALib library. The value of the fitness function is equal to the energy value for the single-pulse and otherwise zero. Findings. The genetic algorithm has been implemented for solving optimization problem of fiber lasers and modifying the algorithm to reduce the calculation time. The parameters of the laser for the scalar model are determined and agreement with the results obtained by the enumeration method is presented. For the hybrid model, a stable pulse with three times the energy was found. Conclusions. In this work, a determination of the optimal parameters for mode-locked fiber lasers based on nonlinear polarization rotation was presented. The problem was solved using a genetic algorithm. This is the first step towards creating a “smart” self-tuning laser

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Feng, Xian, Joanne C. Flanagan, Ken E. Frampton, Periklis Petropoulos, Nicholas M. White, Jonathan H. V. Price, Wei H. Loh, Harvey N. Rutt et David J. Richardson. « Developing Single-Mode Tellurite Glass Holey Fiber for Infrared Nonlinear Applications ». Advances in Science and Technology 55 (septembre 2008) : 108–17. http://dx.doi.org/10.4028/www.scientific.net/ast.55.108.

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We review our progress in developing single-mode tellurite glass holey fiber for infrared nonlinear applications. Tellurite glass preforms with complex holey structure were fabricated by using glass extrusion technique. The fabrication of single-mode tellurite holey fibers with the effective mode area ranging from 2.6-3000mm2 and the effective nonlinearity γ ranging from 0.23- 280W-1km-1 were demonstrated. By controlling the microstructured features in the holey cladding, the dispersion profile and the zero dispersion wavelength of this type of single-material optical fiber were tailored within a broad range. Broadband supercontinuum spectra from 0.9 to 2.5mm were generated from the fabricated fibers by using femtosecond laser. Attenuations due to the impurities, such as transition metal ions, rare-earth ions and hydroxyl groups, were also investigated in the bulk tellurite glass and fiber from visible to mid-infrared regimes.

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Xie, Yufeng. « Analysis of Low-Threshold 1D Perovskite Photonic Crystal Laser ». Highlights in Science, Engineering and Technology 121 (24 décembre 2024) : 267–75. https://doi.org/10.54097/c5sdds38.

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By using the bandgap effect and light localization effect, photonic crystal lasers can decrease the optical mode volume and lower the laser threshold, so satisfying the requirements for device shrinking and photonic integration. Given their wide range of potential applications in fields including light-emitting diodes and sensors, they are attracting considerable interest. The laser threshold is the minimum energy density required to cause laser oscillation and is a crucial specification for the practical application of laser devices. Perovskite materials, equipped with their exceptional optical gain characteristics, are well-suited for the development of low-threshold lasers. By combining them with photonic crystal lasers, it is possible to realize low-threshold or even threshold-free pumped lasers. This paper categorizes photonic crystal lasers according to their photonic crystal structures and examines the advancements in research on perovskite photonic crystal lasers in attaining low minimum thresholds. This work investigates the prospective capabilities of perovskite photonic crystal lasers, with the objective of achieving laser output that is low-threshold or near-zero-threshold, high-power, and of high quality.

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Logvin, Yury, et Hanan Anis. « Similariton pulse instability in mode-locked Yb-doped fiber laser in the vicinity of zero cavity dispersion ». Optics Express 15, n^o 21 (2007) : 13607. http://dx.doi.org/10.1364/oe.15.013607.

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Xu, Peng Fei, Jian Hui Zhang, Ke Zhen Ma, Shu Bin Yan et Wen Dong Zhang. « Resonant Point Tracking and Locking Technique Based on Microsphere Resonator ». Key Engineering Materials 562-565 (juillet 2013) : 553–58. http://dx.doi.org/10.4028/www.scientific.net/kem.562-565.553.

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Abstract. Microsphere resonator is widely studied for the high quality factor Q and small mode volume. Aimed at the sensor applications, the resonant point tracking and locking method is proposed for measuring the resonant frequency shift. To avoid external noises, such as air flow and vibration, spot-packaged coupling structure is adopted. The robustness of microsphere-taper coupling unit is greatly improved. And this lays a foundation for resonant point tracking and locking. By employing modulation method, the demodulation signal is obtained. To lock the laser frequency to resonant point, PID circuits will adjust the center frequency of laser until the intensity of demodulation signal becomes zero. In the experiment, resonant tracking and locking is realized on the rotating platform with rotation rate 2 r/s.

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Chu, Saisai, Anwer Hayat, Fengzhao Cao et Tianrui Zhai. « Single-Mode Lasing in Polymer Circular Gratings ». Materials 14, n^o 9 (29 avril 2021) : 2318. http://dx.doi.org/10.3390/ma14092318.

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In recent years, conjugated polymers have become the materials of choice to fabricate optoelectronic devices, owing to their properties of high absorbance, high quantum efficiency, and wide luminescence tuning ranges. The efficient feedback mechanism in the concentric ring resonator and its circularly symmetric periodic geometry combined with the broadband photoluminescence spectrum of the conjugated polymer can generate a highly coherent output beam. Here, the detailed design of the ultralow-threshold single-mode circular distributed feedback polymer laser is presented with combined fabrication processes such as electron beam lithography and the spin-coating technique. We observe from the extinction spectra of the circular gratings that the transverse electric mode shows no change with the increase of incident beam angle. The strong enhancement of the conjugated polymer photoluminescence spectra with the circular periodic resonator can reduce the lasing threshold about 19 µJ/cm2. A very thin polymer film of about 110 nm is achieved with the spin-coating technique. The thickness of the gain medium can support only the zero-order transverse electric lasing mode. We expect that such a low threshold lasing device can find application in optoelectronic devices.

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Жиленко, Д. Ю., et О. Э. Кривоносова. « Смещения предела устойчивости течения при модуляции скорости вращения ». Письма в журнал технической физики 46, n^o 12 (2020) : 22. http://dx.doi.org/10.21883/pjtf.2020.12.49522.18295.

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The possibilities of the control of stability limit location were experimentally investigated in spherical Couette flow. The inner sphere rotational rate is periodically varied about non-zero average value, the outer sphere is fixed. Instability in the form of travelling azimuthal waves, the same as at stationary rotation, is caused by increasing of average rotational rate. Flow velocity measurements were carried out by laser Doppler anemometer. It was shown, that when modulation frequency become close to eigenfrequency of linear mode, both flow destabilization and stabilization were possible depending on modulation amplitude.

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Steganov, G. B., A. M. Beznyakov et A. V. Nemirov. « Influence of space vehicle remote power supply on thermal regimes of solar batteries ». VESTNIK of Samara University. Aerospace and Mechanical Engineering 21, n^o 1 (27 avril 2022) : 14–23. http://dx.doi.org/10.18287/2541-7533-2022-21-1-14-23.

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The issues of ensuring the functioning of an additional energy-receiving channel for the onboard power supply system of a low-orbit spacecraft are considered. To compensate for the shortage of electricity on board the spacecraft, various options for remote power supply from the system of space power stations transmitting energy to the solar battery by laser radiation during periods of its forced inactivity are possible. Long shadow-sunlight periods of time are a distinctive feature of functioning of low-orbit spacecraft. During these periods the solar battery is idle, and, in addition, even in the daylight portion of the spacecraft's orbit, the energy output from the spacecraft may be reduced to almost zero during the operation of some special systems that require special modes of spacecraft orientation. Reception of energy from a CES with energy flux density higher than that of the solar flux may lead to overheating of the solar battery panel of conventional design, a decrease in its efficiency and even to its failure. Therefore, the analysis of thermal modes of reception and conversion of laser radiation energy which affect the energy efficiency of the solar battery is an important aspect of remote power supply. Relationships of a mathematical model for estimating the available power supply from the solar battery operating in the mode of optimizing control of its power are proposed. The results of approbation of the model for maintaining the safe thermal mode of the solar battery panels during remote power supply of the spacecraft are presented.

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Chen, Jingxuan, Yufei Wang, Ting Fu, Xueyou Wang, Yingqiu Dai et Wanhua Zheng. « Mode degeneracy and enhanced sensitivity in electrically injected PT-symmetric semiconductor laser with a quasi-high-order exceptional point ». Applied Physics Express 14, n^o 12 (23 novembre 2021) : 122005. http://dx.doi.org/10.35848/1882-0786/ac3804.

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Abstract Exceptional points (EPs) can be exploited for a new generation of sensors. We propose an electrically injected parity-time (PT)-symmetric three-ridge semiconductor laser. By introducing the non-zero next-nearest-neighboring coupling coefficient to the Hamiltonian obtained by coupled mode theory, the results of eigenspectra match well with those of numerical simulation obtained by finite element method. Based on the introduced coupling coefficient, we develop our design and obtain a quasi-third-order EP. We analyze the eigenmode splitting vs perturbation strength at the EP, which proves that our design is rather sensitive to the external perturbation and possesses the potential to be applied as active high-sensitive sensors.

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Zhu, Rui, Yaoyao Qi et Jianfei Meng. « Novel nanomaterials based saturable absorbers for passive mode locked fiber laser at 1.5 μm ». Nanotechnology 33, n^o 18 (11 février 2022) : 182002. http://dx.doi.org/10.1088/1361-6528/ac4d59.

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Abstract Compared with continuous wave lasers, ultrafast lasers have the advantages of ultra-short pulse width and ultra-high peak power, and have significant applications in optical communications, medical diagnostics, and precision machining. Saturable absorber (SA) technology is the most effective technique for the generation of ultra-fast lasers, which are based on artificial SAs and natural SAs. Among them, the semiconductor saturable absorber mirror has become the most commonly used form at present. Recently, basic research and application of nanomaterials such as carbon nanotubes (CNTs) and graphene have been developed rapidly. Researchers have found that nanomaterials exhibit extraordinary characteristics in ultrafast photonics, such as the low saturation intensity of CNTs, zero-band gap of graphene, and extremely high modulation depth of the topological insulator nano-films. Since graphene was first reported as an SA in 2009, many other nanomaterials have been successively explored, resulting in the rapid development of novel nanomaterial-based SAs. In this paper, we classified the nanomaterials used in SA mode-locking technology at 1.5 μm and reviewed their research progress with a particular focus on nonlinear optical properties, integration strategies, and applications in the field of ultrafast photonics.

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Eggleston, Bonne, Sergey Varlamov, Jialiang Huang, Rhett Evans, Jonathon Dore et Martin A. Green. « Large Grained, Low Defect Density Polycrystalline Silicon on Glass Substrates by Large-area Diode Laser Crystallisation ». MRS Proceedings 1426 (2012) : 251–56. http://dx.doi.org/10.1557/opl.2012.1260.

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ABSTRACTA new method to form high quality crystalline silicon thin films on cheap glass substrates is developed using a single pass of a line-focus cw diode laser in air. The laser process results in the formation of large high-quality crystals as they grow laterally in the scan direction – seeded by the previously crystallised region. Grains 10 μm in thickness, up to millimetres in length and hundreds of microns in width have been grown with virtually zero detectable intragrain defects. Another mode is found which results in much smaller crystals grown by partial melting. The dominant grain boundaries identified are Σ3 <111> 60° twins. Hall mobilities as high as 470 cm2/Vs have been recorded. A diffused emitter is used to create a p-n junction at the rear of the films which produces open-circuit voltages as high as 539 mV.

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Feng, Rui, Laigui Hu, Youwei Zhang, Muhammad Zaheer, Zhi-Jun Qiu, Chunxiao Cong, Qingmiao Nie, Yajie Qin et Ran Liu. « Direct laser writing of vertical junctions in graphene oxide films for broad spectral position-sensitive detectors ». Nanophotonics 7, n^o 9 (11 août 2018) : 1563–70. http://dx.doi.org/10.1515/nanoph-2018-0070.

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AbstractHeterostructures with built-in electric fields are crucial for charge separation and lateral photovoltaic effect in current position-sensitive detectors (PSDs), which have to be produced by combining semiconductors with metal or other semiconductors to form various vertical junctions (e.g. Schottky junctions) via complicated and high-cost manufacture processes. In the present work, it was found that vertical junctions can be directly written and patterned inside graphene oxide (GO) films with gradient C/O ratios by laser scribing due to the optical filter effect of the films and the formation of reduced GO (rGO) layers. Such junctions were verified to show the capability for high-precision position sensing on the micrometer scale, owing to the lateral photovoltaic effect. These self-powered laser-scribed PSDs can exhibit a small nonlinearity of <5.4%, which is far less than the acceptable level of 15%. A fast response time of about 1 ms can be obtained under a zero bias voltage, which is the fastest speed among the photodetectors based on pure rGO. Electron lateral diffusion in the upper layers of the laser-scribed devices was found to play a main role. These suggest that laser-scribed vertical junctions inside rGO are promising for high-precision displacement sensing, with the capability of low cost, flexibility, and passive operation mode.

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Jiang, Xiantao, Huiling Lu, Qian Li, Hang Zhou, Shengdong Zhang et Han Zhang. « Epsilon-near-zero medium for optical switches in a monolithic waveguide chip at 1.9 μm ». Nanophotonics 7, n^o 11 (11 octobre 2018) : 1835–43. http://dx.doi.org/10.1515/nanoph-2018-0102.

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AbstractA saturable absorber is a building block for integrated ultrafast photonics and passive optical circuits. However, options currently available suffer from the bottlenecks of the necessity for fine control of the material preparation, large optical losses, and compatibility. This paper presents a complementary metal–oxide–semiconductor (CMOS)-compatible alternative based on an epsilon-near-zero (ENZ) medium, in which the real part of the dielectric constant vanishes. Excellent nonlinear optical modulations, including low linear optical losses, low bleaching threshold, moderate optical amplitude modulation, and high modulation speed of indium tin oxide (ITO) in its ENZ region are achieved. The use of ITO as an intracavity saturable absorber for optical switches of integrated waveguide chip lasers at 1.9 μm has been realized. A stable mode-locked waveguide laser with a repetition rate of 6.4 GHz and an average output power of 28.6 mW is achieved via carefully adjusting the intracavity three-surface interferometer (TSI). This work may pave the way for integrated photonics and electro-optics using a CMOS-compatible ENZ medium.

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Yan, Guqi, Samuel Raetz, Jean-Philippe Groby, Aroune Duclos, Alan Geslain, Nikolay Chigarev, Vitalyi E. Gusev et Vincent Tournat. « Estimation via Laser Ultrasonics of the Ultrasonic Attenuation in a Polycrystalline Aluminum Thin Plate Using Complex Wavenumber Recovery in the Vicinity of a Zero-Group-Velocity Lamb Mode ». Applied Sciences 11, n^o 15 (28 juillet 2021) : 6924. http://dx.doi.org/10.3390/app11156924.

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In this paper, we present a method to recover the complex wavenumber dispersion relations using spatial Laplace transform from experimental spatiotemporal signals measured by laser ultrasonic technique. The proposed method was applied on zero-group-velocity Lamb modes in order to extract the ultrasonic attenuation in a polycrystalline aluminum plate of about 70 μm thickness. The difference between the experimental and theoretical Laplace Fourier transforms was minimized in the least square sense to extract the complex amplitudes and complex wavenumbers of the modes at about 40 MHz. The experimental results were compared to values reported in the literature that were measured by other means and those estimated by using the quality factor extracted from a single temporal signal.

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Shang Xin, Li Fan, Ma Zheng-Lei, Huang Tian-Shi, Dang Hao, Li Wei, Yin Wang-Bao, Tian Long, Chen Li-Rong et Zheng Yao-Hui. « Low noise photodetector in 0.1 mHz-1 Hz band ». Acta Physica Sinica 74, n^o 5 (2025) : 0. https://doi.org/10.7498/aps.74.20241635.

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Laser intensity noise suppression in the millihertz frequency band is essential for space-based gravitational wave detection to ensure the sensitivity of the interferometer. Photonic feedback technology is one of the most effective methods for suppressing laser intensity noise. As the first-stage component in the feedback loop, the noise of the photodetector directly couples into the feedback loop, significantly impacting the laser intensity noise. Starting from the requirement to suppress laser intensity noise in the 0.1 mHz-1 Hz frequency band for space-based gravitational wave detection, this paper provides a detailed analysis of the factors influencing the electronics of photodetectors at extremely low frequencies. Leveraging the low dark current characteristic of photodiodes in photovoltaic mode, a zero-bias voltage scheme is adopted to reduce the dark noise of the photodiode. A transimpedance amplification circuit is designed using an integrated operational amplifier with zero offset voltage drift and low-temperature drift metal foil resistors, optimizing the transimpedance capacitor and follower circuit to reduce 1/f noise in the circuit. Active temperature control is employed to stabilize the photodiode's responsivity, and additional measures such as using a self-developed low-noise power supply and shielding against interference are implemented to further reduce noise. Ultimately, an ultra-low electronic noise photodetector operating in the 0.1 mHz-1 Hz frequency band is developed. A self-developed intensity noise evaluation system is used to comprehensively assess the noise in both the time and frequency domains, and experimental results demonstrate the constant noise characteristics of the developed detector. The experimental results show that the electronic noise spectral density of the developed detector reaches 2×10-6V/Hz1/2 in the 0.1 mHz-1 Hz frequency band, and the detector's electronic noise does not vary with optical power. The detector achieves a gain of 35 kV/W at 1064 nm. The noise performance of the detector is two orders of magnitude lower than the laser intensity noise requirement (10-4/Hz1/2) for space-based gravitational wave detection, providing a critical component and technical support for high-gain photonic feedback control and laser intensity noise suppression in space-based gravitational wave detection.

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Petrenko, Mikhail, et Anton Vershovskii. « Towards a Practical Implementation of a Single-Beam All-Optical Non-Zero-Field Magnetic Sensor for Magnetoencephalographic Complexes ». Sensors 22, n^o 24 (15 décembre 2022) : 9862. http://dx.doi.org/10.3390/s22249862.

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We present a single-beam all-optical two-channel magnetic sensor scheme developed for biological applications such as non-zero-field magnetoencephalography and magnetocardiography. The pumping, excitation and detection of magnetic resonance in two cells are performed using a single laser beam with time-modulated linear polarization: the linear polarization of the beam switches to orthogonal every half-cycle of the Larmor frequency. Light with such characteristics can be transmitted over a single-mode polarization-maintaining fiber without any loss in the quality of the polarization characteristics. We also present an algorithm for calculating optical elements in a sensor scheme, the results of measuring the parametric dependences of magnetic resonance in cells, and the results of direct testing of a sensor in a magnetic shield. We demonstrate sensitivity at the level of 20 fT/√Hz in one sensor channel in the frequency range of 80–200 Hz.

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Ostrowski, Mariusz, Bartlomiej Blachowski, Grzegorz Mikułowski et Łukasz Jankowski. « Influence of Noise in Computer-Vision-Based Measurements on Parameter Identification in Structural Dynamics ». Sensors 23, n^o 1 (27 décembre 2022) : 291. http://dx.doi.org/10.3390/s23010291.

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Nowadays, consumer electronics offer computer-vision-based (CV) measurements of dynamic displacements with some trade-offs between sampling frequency, resolution and low cost of the device. This study considers a consumer-grade smartphone camera based on complementary metal-oxide semiconductor (CMOS) technology and investigates the influence of its hardware limitations on the estimation of dynamic displacements, modal parameters and stiffness parameters of bolted connections in a laboratory structure. An algorithm that maximizes the zero-normalized cross-correlation function is employed to extract the dynamic displacements. The modal parameters are identified with the stochastic subspace identification method. The stiffness parameters are identified using a model-updating technique based on modal sensitivities. The results are compared with the corresponding data obtained with accelerometers and a laser distance sensor. The CV measurement allows lower-order vibration modes to be identified with a systematic (bias) error that is nearly proportional to the vibration frequency: from 2% for the first mode (9.4 Hz) to 10% for the third mode (71.4 Hz). However, the measurement errors introduced by the smartphone camera have a significantly lower influence on the values of the identified stiffness parameters than the numbers of modes and parameters taken into account. This is due to the bias–variance trade-off. The results show that consumer-grade electronics can be used as a low-cost and easy-to-use measurement tool if lower-order modes are required.

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Dudley, John M., Salah M. Boussen, David M. J. Cameron et John D. Harvey. « Complete characterization of a self-mode-locked Ti:sapphire laser in the vicinity of zero group-delay dispersion by frequency-resolved optical gating ». Applied Optics 38, n^o 15 (20 mai 1999) : 3308. http://dx.doi.org/10.1364/ao.38.003308.

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Li, Guang. « A High Speed and Ultra Long-Haul Radio-Over-Fiber System Employing Dual Photoelectric Arms Coherent Modulation and Optical Duo-Binary Coding ». Advanced Materials Research 988 (juillet 2014) : 544–47. http://dx.doi.org/10.4028/www.scientific.net/amr.988.544.

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A novel high speed and ultra long-haul radio-over-fiber (ROF) system based on Dual Photoelectric Arms Coherent Modulation (DPACM) and Optical Duo-Binary Coding (ODBC) is proposed, and demonstrated. The signal spectrum bandwidth, generated by ODBC based on the first order DPACM, is half of non-return-to-zero (NRZ ) signal spectrum bandwidth. The secondary order DPACM generates a 40-GHz Millimeter-wave (mm-wave) that is transmitted over fiber (ROF). The simulation results show that, the bit rate can be up to 40 Gbps and the transmission distance is over 1500 Km, based on the ROF system with a 0 dBm continuous-wave laser source, multiple stages Er-Doped Fiber Amplifier (EDFA), a standard single mode fiber (SSMF) with a dispersion of 17 ps/nm/Km and a attenuation of 0.2 dB/Km.

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Aalizadeh, Majid, Andriy E. Serebryannikov, Ekmel Ozbay et Guy A. E. Vandenbosch. « A simple Mie-resonator based meta-array with diverse deflection scenarios enabling multifunctional operation at near-infrared ». Nanophotonics 9, n^o 15 (29 septembre 2020) : 4589–600. http://dx.doi.org/10.1515/nanoph-2020-0386.

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AbstractDeflection, a basic functionality of wavefront manipulation is usually associated with the phase-gradient metasurfaces and the classical blazed gratings. We numerically and experimentally demonstrate an unusually wideband and simultaneously wide-angle deflection achieved at near-infrared in reflection mode for a periodic (nongradient), ultrathin meta-array comprising only one silicon nanorod (Mie resonator) per period. It occurs in the range where only the first negative diffraction order and zero order may propagate. Deflection serves as the enabler for multifunctional operation. Being designed with the main goal to obtain ultra-wideband and wide-angle deflection, the proposed meta-array is also capable in spatial filtering and wide-angle splitting. Spatial filtering of various types can be obtained in one structure by exploiting either deflection in nonzero diffraction orders, or the specular-reflection (zero-order) regime. Thus, the role of different diffraction orders is clarified. Moreover, on–off switching of deflection and related functionalities is possible by changing polarization state of the incident wave. The suggested device is simple to fabricate and only requires cost-effective materials, so it is particularly appropriate for the large-area fabrication using nanoprint lithography. Ultra-wideband wide-angle and other deflection scenarios, along with the other functionalities, are promising for applications in optical communications, laser optics, sensing, detection, and imaging.

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Hasan Sohag, Md S., et K. H. Kabir. « Tellurite-filled hexa-circular-shaped PCF with highly nonlinearity, birefringent and near-zero dispersion profile for optical communications ». Journal of Ovonic Research 18, n^o 4 (31 juillet 2022) : 527. http://dx.doi.org/10.15251/jor.2022.184.527.

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This manuscript focuses on devising a Tellurite-filled circular-timbered PCF that shows considerably highly birefringent and nonlinear characteristics. The impacts of numerous design parameters, such as birefringence (Br), nonlinear coefficients (NLC), confinement loss (CL), effective mode area (EMA), dispersion, numerical aperture (NA), etc. of the fiber are extensively inspected employing the commercially accessible and simulation- friendly COMSOL Software. Besides, the pertinent modal properties of the modeled fiber are rigorously characterized by operating the full-vector finite element method (FEM) with a perfectly matched layer (PML) boundary condition. The simulated findings affirm that the developed fiber exemplifies an ultra-high Br and NLC of 0.0924 and 18900 W-1Km-1 consecutively, at the operational wavelength of 1.55μm. Notably, the offered PCF also reveals a relatively lower CL, a negative-sloping dispersion and a higher EMA at the same wavelength. The pragmatic execution of the modeled fiber is expected to be doable applying the existing fabrication approaches and it can be applied in miscellaneous identical optical domains, namely polarization retention in long-distance communications, optical switching, sensor and laser layout, supercontinuum generation for frequency metrology and so forth.

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Kim, Gaul et Köhler. « Improved SH0 Guided Wave Transducers Based on Piezoelectric Fiber Patches ». Sensors 19, n^o 13 (6 juillet 2019) : 2990. http://dx.doi.org/10.3390/s19132990.

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A piezoelectric fiber patch (PFP) is a transducer type that is suitable for guided-wave-based structural health monitoring (SHM) due to its light, thin, and flexible characteristics. In our previous work, a PFP-based transducer design for selective excitation of the zero-order shear horizontal wave mode (SH0) was introduced (shear horizontal PFP (SHPFP)). In this work, two modified SH0 wave PFP transducer designs are proposed: the rounded corner design and the dual design. The degree of improvement is determined by a numerical simulation and the dual design—the design with the most promise—is experimentally realized. Laser Vibrometry measured the generated wave field, confirming the results from the simulation. The new designs can generate an almost pure SH0 wave. The dual design has a very strong directivity that is useful for several guided-wave-based SHM applications. The conclusions on the design’s properties as a transmitter are also valid for its properties as a sensor due to the reciprocity of piezoelectric transducers.

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Tagawa, N., et M. Hashimoto. « Self-Loading Slider Dynamics for Noncontact Start Stop Operation With Negative Pressure Air-Lubricated Slider Bearing in Magnetic Disk Storage ». Journal of Tribology 111, n^o 4 (1 octobre 1989) : 698–702. http://dx.doi.org/10.1115/1.3261997.

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This paper proposes self-loading flying head slider mechanisms to be used for information storage on magnetic disk media under noncontact start/stop mode conditions. The mechanisms consist of a zero-load negative pressure air-lubricated slider bearing, a slider suspension mechanism, and a twin-structure piezoelectric actuator as the head loading mechanism. Experimental research was carried out on fundamental flying characteristics for the slider. The dynamics of a self-loading/unloading negative pressure air-lubricated slider bearing were successfully studied in detail with a laser Doppler vibrometer. No intermittent contact between head and disk was observed in either the self-load or unload cases. A theoretical study on the self-loading phenomenon was carried out, and its conclusions were in good agreement with the experimental results. This suggests the feasibility of achieving a high head/disk interface reliability and, in particular, of overcoming problems regarding stiction and tribology between head and disk.

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ZHU, J., W. J. JIE, X. H. WEI, W. F. QIN, Y. ZHANG et Y. R. LI. « ENHANCED DIELECTRIC CHARACTERISTICS OF MANGANESE-DOPED BZT THIN FILMS ». Surface Review and Letters 15, n^o 01n02 (février 2008) : 29–33. http://dx.doi.org/10.1142/s0218625x08010907.

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Ba ( Zr 0.2 Ti 0.8) O 3 (BZT) and 2 mol% Mn additional doped BZT ( Mn -BZT) thin films were deposited by pulsed laser deposition technique under the same growth conditions on LaAlO 3 substrates with the bottom electrodes of LaNiO 3. The microstructure of the films was characterized by X-ray diffraction (XRD) in the mode of θ–2θ scan and Φ-scan. The results indicated that BZT film was (001)-oriented_with an in-plane relationship of BZT[100]//LNO[100]//LAO[100]. The Mn -BZT film exhibited higher dielectric constant of 225 at zero electric field, larger dielectric tunability of 59.4%, and lower dielectric loss of 1.8% under an applied electric field of 720 kV/cm. The figure of merit for BZT thin film increased from 19.8 to 33 by Mn doping. The enhanced dielectric behavior by Mn doping could be mainly attributed to the decrease of oxygen vacancies and the reorientation of the dipolar defect complex of [Formula: see text].

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