Journal articles: 'Multi-Mode interference (MMI) coupler'

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Kumari, Sneha, Akhilesh Kumar Pathak, Rahul Kumar Gangwar, and Sumanta Gupta. "Performance Analysis of SiGe-Cladded Silicon MMI Coupler in Presence of Stress." Computation 11, no. 2 (February 14, 2023): 34. http://dx.doi.org/10.3390/computation11020034.

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In this study, we demonstrate the influence of operating temperature variation and stress-induced effects on a silicon-on-insulator (SOI)-based multi-mode interference coupler (MMI). Here, SiGe is introduced as the cladding layer to analyze its effect on the optical performance of the MMI coupler. SiGe cladding thickness is varied from 5 nm to 40 nm. Characterization of the MMI coupler for ridge waveguides with both rectangular and trapezoidal sidewall slope angle cross-sections is reviewed in terms of power splitting ratio and birefringence. Stress-induced birefringence as a function of operating temperature and cladding thickness for fundamental mode have been calculated. A trapezoidal waveguide with 40 nm of cladding thickness induces more stress and, therefore, affects birefringence more than a rectangular waveguide of any thickness. Simulation results using the finite element method (FEM) confirmed that operating temperature variation, upper cladding thickness, and its stress effect are significant parameters that drastically modify the performance of an MMI coupler.

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Moskalev, Dmitrii, Andrei Kozlov, Uliana Salgaeva, Victor Krishtop, Anatolii V. Perminov, and Vladimir Venediktov. "A Semi-Analytical Method for the S-Parameter Calculations of an N × M Multimode Interference Coupler." Photonics 10, no. 11 (November 14, 2023): 1260. http://dx.doi.org/10.3390/photonics10111260.

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A semi-analytical method for the S-parameter calculations of an N×M multimode interference coupler (MMI coupler) is presented. The proposed semi-analytical method is based on the mode decomposition and utilizes an effective index method to approximate the channel waveguide using an equivalent slab waveguide whose modes are described by exact analytic expressions. In comparison to the commonly used beam propagation method (BPM) and finite difference time domain method, which require significant time and computational resources, the proposed method accelerates the design process of photonic integrated circuits and basic building blocks such as an MMI coupler. The simulation results obtained using the developed method and the BPM were compared and showed very similar outcomes for different topologies of the MMI coupler. The key advantage of the proposed semi-analytical method over other analytical models is its ability to accurately simulate MMI couplers with an arbitrary position and number of input and output waveguides. In addition, this method can be extended using the theory of local coupled modes by taking into account the reflections from the end face of the MMI box.

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Yasui, Takashi, Jun-ichiro Sugisaka, and Koichi Hirayama. "Structural Optimization of an Optical 90 Degree Hybrid Based on a Weakly-guided 4x4 Multimode Interference Coupler Using a Parallelized Real-coded Micro-genetic Algorithm." Applied Computational Electromagnetics Society 36, no. 5 (June 14, 2021): 526–32. http://dx.doi.org/10.47037/2020.aces.j.360506.

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The optimal design of a 4x4 multimode interference (MMI) coupler as an optical 90° hybrid based on a weakly-guided optical waveguide was considered. Seven geometrical parameters of a 4x4 MMI coupler were optimized by a real-coded micro-genetic algorithm, and parallelized using a message-passing interface. The beam-propagation method was used to evaluate the fitness of the MMI coupler in the optimization process. The optimized 4x4 MMI coupler showed a common-mode rejection ratio greater than 28.9 dBe and a phase error less than 2.52° across a wavelength range of 1520 to 1580 nm, which satisfied typical system requirements. The optimization process was executed on a Beowulf-style cluster comprising five identical PCs, and its parallel efficiency was 0.78.

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DARMAWAN, S., S. Y. LEE, C. W. LEE, and M. K. CHIN. "TRANSFORMATION OF DIRECTIONAL COUPLERS TO MULTI-MODE INTERFEROMETERS BASED ON RIDGE WAVEGUIDES AND ITS APPLICATIONS." Journal of Nonlinear Optical Physics & Materials 14, no. 02 (June 2005): 221–35. http://dx.doi.org/10.1142/s0218863505002657.

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We present a comparison of directional couplers and multi-mode interferometers based on the unique properties of high-index contrast ridge waveguides. The two devices are intimately related as the MMI is structurally derived from the DC. For the first time, the continuous evolution from the two-mode coupling characteristic of DC to the multi-mode mixing and interference characteristic of MMI is shown. We show that practical directional couplers with reasonable gap size can also be quite compact and have the same coupling length for both TE and TM polarizations. Consequently, the DC can be just as polarization insensitive as the MMI. These features, however, require careful design control involving a large set of design parameters. On top of that, we also show a novel design of polarization splitter based on both DC and MMI. By comparison, the MMI design is more robust and involves fewer design variables.

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Le, Trung-Thanh. "Electromagnetically Induced Transparency (EIT) Like Transmission Based on 3 × 3 Cascaded Multimode Interference Resonators." Micromachines 9, no. 8 (August 20, 2018): 417. http://dx.doi.org/10.3390/mi9080417.

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We propose a method for generating the electromagnetically induced transparency (EIT) like-transmission by using microring resonator based on cascaded 3 × 3 multimode interference (MMI) structures. Based on the Fano resonance unit created from a 3 × 3 MMI coupler with a feedback waveguide, two schemes of two coupled Fano resonator unit (FRU) are investigated to generate the EIT like transmission. The theoretical and numerical analysis based on the coupled mode theory and transfer matrix is used for the designs. Our proposed structure has advantages of compactness and ease of fabrication. We use silicon waveguide for the design of the whole device so it is compatible with the existing Complementary Metal-Oxide-Semiconductor (CMOS) circuitry foundry. The fabrication tolerance and design parameters are also investigated in this study.

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Lenstra, Daan. "Rate-Equation Analysis for a Coupled-Cavity Laser with MMI Anti-Phase Coupler." International Journal of Engineering and Technologies 8 (August 2016): 14–23. http://dx.doi.org/10.18052/www.scipress.com/ijet.8.14.

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Rate equations are derived for the coupled-cavity laser with a multimode-interference coupler. A strategy and scheme is indicated for iterative self-consistent numerical solution of the steady-state equations. The presence of the linewidth-enhancement parameter is explicitly taken into account. Locking in stable single-mode anti-phase operation is numerically demonstrated and locking ranges are given. Numerical results are given for the output power and the operation frequency as functions of the pump strengths of the individual lasers. The shapes of output-intensity curves agree well with measured curves.

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Lenstra, Daan. "Rate-Equation Analysis for a Coupled-Cavity Laser with MMI Anti-Phase Coupler." International Journal of Engineering and Technologies 8 (August 9, 2016): 14–23. http://dx.doi.org/10.56431/p-24r2x0.

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Rate equations are derived for the coupled-cavity laser with a multimode-interference coupler. A strategy and scheme is indicated for iterative self-consistent numerical solution of the steady-state equations. The presence of the linewidth-enhancement parameter is explicitly taken into account. Locking in stable single-mode anti-phase operation is numerically demonstrated and locking ranges are given. Numerical results are given for the output power and the operation frequency as functions of the pump strengths of the individual lasers. The shapes of output-intensity curves agree well with measured curves.

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Chiu, C. L., and Yen-Hsun Liao. "The Critical Adiabatic Linear Tapered Waveguide Combined with a Multimode Waveguide Coupler on an SOI Chip." International Journal of Optics 2019 (November 11, 2019): 1–10. http://dx.doi.org/10.1155/2019/4270612.

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A multimode waveguide interference (MMI) coupler is combined with a critical linear tapered waveguide on a silicon-on-insulator (SOI) chip. When the TE0 mode is a critical adiabatic mode conversion from a single-mode waveguide to an extreme linear tapered waveguide combined with an MMI, this linear tapered waveguide is achieved to the maximum divergence angle (i.e., the shortest length). The maximum divergence angle is expressed by θ ≤ 2 tan−1[(0.35Wmmi − Ws)/(0.172Lmmi)] under a 1 × 1 MMI combined with this critical linear tapered waveguide. The expression formula is demonstrated by three different widths of a 1 × 1 MMI of 4 μm/8 μm/12 μm combined with the critical linear tapered waveguide. So, the maximum divergence angle is obtained at θ = 16°/14°/8°, with respect to this linear tapered waveguide loss of 0.022 dB/0.172 dB/0.158 dB, and this linear tapper length is reduced by 93.7%/92.9%/87.5% than the divergence angle θ = 1°. The output power of a 1 × 1 MMI combined with a critical linear tapered waveguide is enhanced at least 1.5 times under 0.95 above condition.

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Brand, Omer, Benjamin Wolftson, and Dror Malka. "A Compact Polarization MMI Combiner Using Silicon Slot-Waveguide Structures." Micromachines 14, no. 6 (June 6, 2023): 1203. http://dx.doi.org/10.3390/mi14061203.

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The study of designing a compact transverse electric (TE)/transverse magnetic (TM) polarization multimode interference (MMI) combiner based on silicon slot-waveguide technology is proposed for solving the high demands for high-speed ability alongside more energy power and minimizing the environmental impact of power consumption, achieving a balance between high-speed performance and energy efficiency has become an important consideration in an optical communication system. The MMI coupler has a significant difference in light coupling (beat-length) for TM and TE at 1550 nm wavelength. By controlling the light propagation mechanism inside the MMI coupler, a lower order of mode can be obtained which can lead to a shorter device. The polarization combiner was solved using the full-vectorial beam propagation method (FV-BPM), and the main geometrical parameters were analyzed using Matlab codes. Results show that after a short light propagation of 16.15 μm, the device can function as TM or TE combiner polarization with an excellent extinction ratio of 10.94 dB for TE mode and 13.08 dB for TM mode with low insertion losses of 0.76 dB (TE) and 0.56 dB (TM) and the combiner function well over the C-band spectrum. The polarization combiner also has a robust MMI coupler length tolerance of 400 nm. These attributes make it a good candidate for using this proposed device in photonic integrated circuits for improving power ability at the transmitter system.

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Liao, Jiali, Linke Liu, Yanling Sun, Zihao Wang, Wei Li, Jinrong Lan, Lin Ma, and Zhenzhong Lu. "Polarization-Insensitive Lithium Niobate-on-Insulator Interferometer." Micromachines 15, no. 8 (July 30, 2024): 983. http://dx.doi.org/10.3390/mi15080983.

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The key components of a polarization-independent electro-optic (EO) interferometer, including the beam splitter, mode converter, and directional coupler, are designed based on a lithium niobate (LN) platform on an integrated insulator to ensure high extinction ratios. By elaborately designing the geometric structure of the multimode interference (MMI) coupler, beam splitting of equal proportions and directional coupling of higher-order modes are realized. The most prominent characteristic of the proposed interferometer is polarization insensitivity, which is realized by converting TM polarization into TE polarization using a mode converter, providing conditions for the study of light with different polarizations. At 1550 nm, the visibility of the interferometer is 97.59% and 98.16% for TE and TM, respectively, demonstrating the high performance of the proposed LN polarization-independent interferometer.

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Lu, Ziqing, Qin Han, Han Ye, Shuai Wang, and Feng Xiao. "Manufacturing Tolerance Analysis of Deep-Ridged 90° Hybrid Based on InP 4 × 4 MMI." Photonics 7, no. 2 (April 3, 2020): 26. http://dx.doi.org/10.3390/photonics7020026.

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An optical 90° hybrid based on an InGaAsP/InP deep-ridged 4 × 4 multimode interference (MMI) coupler is proposed and fabricated. Manufacturing tolerances on structural parameters of the 90° hybrid including multimode waveguide width and length, waveguide core thickness, and refractive index are analyzed over the whole C-band using a three-dimensional beam propagation method (3D BPM). The simulation results show that the 90° hybrid is insensitive to the interference length with a deviation of 10 μm. However, the width fluctuations produce far stronger performance variations than length fluctuations. The common-mode rejection ratios (CMRRs) are always above 40 dB, and the phase error (PE) is always below 2.5° with the fluctuations of the refractive index by 0.01 and the thickness by 0.1 μm of the core layer. The fabricated device exhibited a quadrature phase response with a high common-mode rejection ratio of more than 25 dB and a small phase error of less than 5° from 1545 nm to 1560 nm.

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Li, Dechen, Jinye Li, Run Li, and Jianguo Liu. "The Design and Characterization of an Ultra-Compact Asymmetrical Multimode Interference Splitter on Lithium Niobate Thin Film." Photonics 11, no. 1 (January 5, 2024): 60. http://dx.doi.org/10.3390/photonics11010060.

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We propose and demonstrate a high-performance asymmetrical multimode interference splitter on X-cut lithium niobate on insulator (LNOI) with an ultra-compact size of 5.8 μm × (26.4–35.6) μm. A rectangle with a small region is removed from the upper left corner of the multimode interference (MMI) coupler to achieve a variable splitting ratio. Here, we design and characterize MMIs in six different distribution ratios ranging from 50:50 to 95:5 on a 600 nm thick LNOI. Based on the cascade structure, the linear fitting method accurately shows the device loss (~0.1–0.9 dB). Our fabricated devices demonstrate robustness across a 30 nm optical bandwidth (1535–1565 nm). In addition, we numerically simulate the Z-cut LNOI, showing that the structure corresponding to the TM mode can also achieve a good variable splitting ratio.

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Ji, Peng, Shiru Jiang, and Sang-Shin Lee. "Fiber Reshaping-Based Refractive Index Sensor Interrogated through Both Intensity and Wavelength Detection." Sensors 19, no. 11 (May 30, 2019): 2477. http://dx.doi.org/10.3390/s19112477.

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A fiber reshaping-based refractive index (RI) sensor is proposed relying on both optical intensity variation and wavelength shift. The objective of this study is to completely reshape the core and to ultimately mimic a coreless fiber, thereby creating a highly efficient multimode interference (MMI) coupler. Thus, propagation modes are permitted to leak out into the cladding and eventually escape out of the fiber, depending on the surrounding environment. Two interrogation mechanisms based on both the intensity variation and wavelength shift are employed to investigate the performance of the RI sensor, with the assistance of leaky-mode and MMI theories. By monitoring the output intensity difference and the wavelength shift, the proposed RI sensor exhibits high average sensitivities of 185 dB/RIU and 3912 nm/RIU in a broad range from 1.339 to 1.443, respectively. The operating range and sensitivity can be adjusted by controlling the interaction length, which is appealing for a wide range of applications in industry and bioscience research.

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Truong, Dung Cao, Dao Anh Vu, and Chung Vu Hoang. "Two Mode - (De)muxer Based on a Symmetric Y Junction Coupler, a $2\times 2$ MMI Coupler and a Ridge Phase Shifter Using Silicon Waveguides for WDM Applications." Communications in Physics 27, no. 4 (December 15, 2017): 327. http://dx.doi.org/10.15625/0868-3166/27/4/10883.

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In this paper, we introduce a new two-mode (de)multiplexer based on the silicon-on-insulator (SOI) platform. The device is built on a symmetric Y-junction, a 2×2 multimode interference (MMI) waveguide and a phaseshifter in the form of a ridge waveguide which is designed using 3D scalar beam propagation method (BPM). The phase evolution in the structure is discussed in details. Simulation results show that the device can operate in a wide wavelength range (150 nm) with a low insertion loss and small crosstalk. Large fabrication tolerance to the width of the input waveguide up to 100 nm is achieved, which is compatible to the current CMOS manufacturing technologies for the photonic integrated circuits. Furthermore, the small footprint (4µm×286µm) makes the device suitable for applications in high bitrate and compact on-chip silicon photonic integrated circuits.

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Zhao, Zhizun, Zhen Li, Jiaqi Niu, Gaolu Zhang, Hongliang Chen, Xin Fu, and Lin Yang. "Eight-Channel LAN WDM (De)Multiplexer Based on Cascaded Mach–Zehnder Interferometer on SOI for 400GbE." Photonics 9, no. 4 (April 11, 2022): 252. http://dx.doi.org/10.3390/photonics9040252.

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In this paper, we design and experimentally demonstrate an eight-channel cascaded Mach–Zehnder interferometer (MZI) based Local Area Network (LAN) Wavelength Division Multiplexing (WDM) (de)multiplexerwith channel spacing of 800 GHz on a silicon-on-insulator. By cascading a three-stage MZI, eight target wavelengths are (de)multiplexed. The length difference of the third-stage MZI delay arms is adjusted so that the output channels skip the guard band. In order to keep the central wavelength of each channel from shifting, we utilize a wide waveguide for the phase delay arm in MZI to achieve large fabrication tolerance, and the multi-mode interference (MMI) couplers as power splitters with weak dispersions. The measurement results of the fabricated device show the precise wavelength alignment over the whole working wavelength range.

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Crespo-Poveda, Antonio, Alberto Hernández-Mínguez, Klaus Biermann, Abbes Tahraoui, Bernardo Gargallo, Pascual Muñoz, Paulo V. Santos, Andrés Cantarero, and Maurício M. de Lima. "Tunable Interferometers Driven by Coherent Surface Acoustic Phonons." MRS Advances 1, no. 22 (2016): 1651–56. http://dx.doi.org/10.1557/adv.2016.234.

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ABSTRACTWe demonstrate a compact tunable photonic modulator driven by surface acoustic waves (SAWs) in the low GHz frequency range. The device follows a well-known Mach-Zehnder interferometer (MZI) structure with three output channels, built upon multi-mode interference (MMI) couplers. The light continuously switches paths between the central and the side channels, avoiding losses and granting a 180◦-dephasing synchronization between them. The modulator was monolithically fabricated on (Al,Ga)As, and can be used as a building block for more complex photonic functionalities. It can also be implemented in other material platforms such as Silicon or (In,Ga)P. Light modulated at multiples of the fundamental acoustic frequency can be accomplished by adjusting the applied acoustic power. An excellent agreement between theory and experiment is achieved.

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Guo, Fei, Dan Lu, Hao Song, Yueying Niu, Daibing Zhou, and Lingjuan Zhao. "A Compact Triplexer Based on InP/InGaAsP-MMI Coupler with Channel-Shaped Core Layer for 50G PON." Photonics 11, no. 3 (March 4, 2024): 232. http://dx.doi.org/10.3390/photonics11030232.

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A novel wavelength triplexer based on Channel-Shaped Multimode Interference (C-MMI) structures on the InP platform is proposed for multi-channel integration compatibility in a 50G passive optical network (PON) system. Performance analysis of the proposed device is carried out by using the 3D Beam Propagation Method (3D-BPM), which shows excellent properties with insertion loss < 0.5 dB and low crosstalk < −14 dB for the 1342 nm in the Original band (1260–1360 nm), 1490 nm in the Short wavelength band (1460–1530 nm), and 1577 nm in the Long wavelength band (1565–1625 nm), also known as the OSL wavelengths band. Furthermore, the passbands of the three downlink channels of 1342 nm, 1490 nm, and 1577 nm, reach 14 nm, 20 nm, and 64 nm, respectively, which is wide enough to meet the 50G PON optical line terminal (OLT) requirement. Additionally, the proposed device is extremely compact with a total length of only 448 μm, making it attractive in the monolithic integrated laser chip and OLT packaged module.

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Chaen, Yutaka, Kazuhiro Tanabe, Haisong Jiang, and Kiichi Hamamoto. "Low wavelength dependency design for MMI (multi-mode interference) mode converter." IEICE Electronics Express 12, no. 20 (2015): 20150727. http://dx.doi.org/10.1587/elex.12.20150727.

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Sakamoto, Junji, Takashi Goh, Satomi Katayose, Ryoichi Kasahara, and Toshikazu Hashimoto. "Shape-optimized multi-mode interference for a wideband visible light coupler." Optics Communications 433 (February 2019): 221–25. http://dx.doi.org/10.1016/j.optcom.2018.09.068.

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Ma, Ze-Long, Tian-Xu Zhao, Wei-Yi Hong, Hu Cui, Zhi-Chao Luo, Wen-Cheng Xu, and Ai-Ping Luo. "Multi-Wavelength Spatiotemporal Mode-Locked Fiber Laser at 1.55 μm." Photonics 9, no. 10 (October 4, 2022): 723. http://dx.doi.org/10.3390/photonics9100723.

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We propose and demonstrate an effective and simple multi-wavelength spatiotemporal mode-locked (STML) laser. The laser introduces a multimode interference (MMI) effect using the core diameter mismatch of the fibers, thus enabling simultaneous mode-locking at multiple wavelengths. For the multi-wavelength mode-locking, each wavelength exists a matching pulse sequence, and different wavelengths can possess the same pulse state or different states. Meanwhile, at the dual-wavelength operation, by adjusting the polarization controllers, not only the central wavelength can be continuously adjusted from 1552.93 nm to 1572.64 nm, but also the wavelength interval can be adjusted from 2 nm to 19 nm, which benefits from the tunability of the MMI effect. Moreover, the spectral channels can be consecutively increased from 2 to 4. The obtained results provide a platform for understanding and studying the multi-wavelength STML properties. This flexible all-fiber laser has great potential for applications in the fields of optical signal processing, fiber sensing, and information coding.

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Koompai, Natnicha, Papichaya Chaisakul, Pichet Limsuwan, Xavier Le Roux, Laurent Vivien, and Delphine Marris-Morini. "Design and Simulation Investigation of Si3N4 Photonics Circuits for Wideband On-Chip Optical Gas Sensing around 2 µm Optical Wavelength." Sensors 21, no. 7 (April 3, 2021): 2513. http://dx.doi.org/10.3390/s21072513.

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We theoretically explore the potential of Si3N4 on SiO2 waveguide platform toward a wideband spectroscopic detection around the optical wavelength of 2 μm. The design of Si3N4 on SiO2 waveguide architectures consisting of a Si3N4 slot waveguide for a wideband on-chip spectroscopic sensing around 2 μm, and a Si3N4 multi-mode interferometer (MMI)-based coupler for light coupling from classical strip waveguide into the identified Si3N4 slot waveguides over a wide spectral range are investigated. We found that a Si3N4 on SiO2 slot waveguide structure can be designed for using as optical interaction part over a spectral range of interest, and the MMI structure can be used to enable broadband optical coupling from a strip to the slot waveguide for wideband multi-gas on-chip spectroscopic sensing. Reasons for the operating spectral range of the system are discussed.

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Shibata, Y., M. Naganuma, S. Oku, and M. Yamamoto. "Reflection characteristics and cascadability of a multi-mode interference 3 dB coupler." IEE Proceedings - Optoelectronics 149, no. 5 (December 1, 2002): 217–21. http://dx.doi.org/10.1049/ip-opt:20020497.

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Kim, Jee Myung, Junghyun Wee, and Kara Peters. "Demonstration of Coherent Interference between Acoustic Waves Using a Fiber Ring Resonator." Sensors 22, no. 11 (May 30, 2022): 4163. http://dx.doi.org/10.3390/s22114163.

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Optical fibers were previously demonstrated to propagate and detect acoustic modes that were converted from Lamb waves for structural health-monitoring applications; typically, a fiber Bragg grating sensor in the optical fiber is used to detect acoustic modes. Acoustic modes can transfer from one fiber to another through a simple adhesive bond coupler, preserving the waveform of the acoustic mode. This paper experimentally investigates the coherence of acoustic waves through the adhesive coupler, using a fiber ring resonator (FRR) configuration. This configuration was chosen because the wave coupled to the second fiber interferes with the original wave after it encircles the fiber ring. We performed this experiment using different geometries of optical fibers in the ring, including a standard single-mode optical fiber, a hollow silica capillary tube, and a large-diameter multi-mode fiber. The results demonstrate that the acoustic wave, when transferring through an adhesive coupler, interferes coherently even when the main and ring fibers are of different types. Finally, we demonstrate that the FRR can be applied for sensing applications by measuring the mode attenuations in the ring due to a changing external environment (water-level sensing) and measuring the optical-path length change in the ring (temperature sensing).

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Pant, Bharat, Weiwei Zhang, Denh Tran, Mehdi Banakar, Han Du, Xingzhao Yan, Callum G. Littlejohns, Graham T. Reed, and David J. Thomson. "Enhanced efficiency thermo-optic phase-shifter by using multi-mode-interference device." EPJ Web of Conferences 238 (2020): 01007. http://dx.doi.org/10.1051/epjconf/202023801007.

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We demonstrate a method for power reduction in thermo-optic based Mach-Zehnder interferometer (MZI) by using the multimode region of a 2x2 Multi-Mode-Interferometer (MMI) as the modulation region. The light is circulated through the same multimode region twice and therefore utilizes the already present change in temperature leading to additional phase change, and an increase in efficiency. Power saving of 29.6% compared to a conventional thermo-optic phase shifter using single mode waveguides has been experimentally demonstrated. The reported devices show minimal insertion loss penalty compared to generic devices and do not add any additional fabrication complexity. Such an approach could also be applied to higher speed devices, for example those employing free carrier effects.

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Royon, Maxime, Thomas Blanchet, Muhammad Adnan, Damien Jamon, François Royer, Francis Vocanson, Emmanuel Marin, et al. "Multi-Mode Interferometry: Application to TiO2–SiO2 Sol-Gel Waveguide-Based Sensing in the Aerospace Domain." Aerospace 8, no. 12 (December 18, 2021): 401. http://dx.doi.org/10.3390/aerospace8120401.

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The optimization of a 2D optical sensor based on TiO2–SiO2 sol-gel waveguides for damage detection in the aerospace domain was performed in the framework of the ADD-ON European project. The sensor is based on the transportation of visible light along numerous waveguides, and damage is detected and localized through the monitoring of the output light from the waveguide grid. In this work, we have developed an architecture, inspired by a multi-mode interferometer (MMI), allowing us to efficiently multiply the number of waveguides that can be probed by a single optical source. For this, the beam propagation method (BPM) was used to model a rectangular MMI coupler (40 × 5624 µm2) operating in the visible region (600 nm), ensuring the propagation of light into three waveguides. The conceived device was then manufactured by UV photolithography (direct laser writing technique). The simulations and experimental results show that light transport into this architecture allows for the successful simultaneous probing of three waveguides. By complexifying the device structure, successful MMI couplers were easily manufactured, allowing us to probe 9, 15, or 45 TiO2–SiO2 waveguides with a unique light source. Finally, a further investigation regarding 24 consecutive thermal cycles from −40 °C to 60 °C, representative of the temperature changes during aircraft cruising, was performed. This study reveals that TiO2–SiO2 sol-gel waveguides are not mechanically damaged by temperature changes, while the light guidance remains unaffected, confirming that this sensor is very promising for aerospace applications. Since a single source can monitor several guides, the production of more compact, low-cost, and less intrusive sensors can be achieved by fulfilling structural health monitoring requirements.

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Liu, Li, Wan-Ting Chen, Jia Zhao, and Chen Zhang. "Two Structural Designs of Broadband, Low-Loss, and Compact TM Magneto-Optical Isolator Based on GaAs-on-Insulator." Nanomaterials 14, no. 5 (February 21, 2024): 400. http://dx.doi.org/10.3390/nano14050400.

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Integrated optical isolators are important building blocks for photonic integrated chips. Despite significant advances in isolators integrated on silicon-on-insulator (SOI) platforms, integrated isolators on GaAs-on-insulator platforms are rarely reported. In this paper, two structural designs of optical isolators based on the TM basic mode of GaAs-on-insulator are proposed. The non-reciprocal phase shift (NRPS) of GaAs/Ce:YIG waveguides with different geometric structures are calculated using numerical simulation. The isolators achieve 35 dB isolation bandwidths greater than 53.5 nm and 70 nm at 1550 nm, with total insertion losses of 2.59 dB and 2.25 dB, respectively. A multi-mode interferometric (MMI) coupler suitable for these two structures is proposed. In addition, suitable manufacturing processes are discussed based on the simulated process tolerances.

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Fang, Yihong, Kunhua Wen, Zhengfeng Li, Bingye Wu, and Zicong Guo. "Plasmonic refractive index sensor with multi-channel Fano resonances based on MIM waveguides." Modern Physics Letters B 34, no. 16 (March 31, 2020): 2050173. http://dx.doi.org/10.1142/s0217984920501730.

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A multi-channel Fano resonant structure is proposed and analyzed based on subwavelength metal–insulator–metal (MIM) waveguides. First, two MIM output ports associated with specific side-coupled cavities are designed to locate at the center and quarter positions of an end-coupled cavity, respectively. Since the interference between the dark and bright modes, dual-channel Fano resonances with asymmetrical lines shapes are obtained at both ports, respectively. High sensitivity and figure of merits are investigated. Besides, phase shifts are also investigated leading to positive and negative group delays available at the Fano peaks and dips, respectively. Likewise, two extra output ports with identical resonant cavities are placed on the other side of the end-coupled cavity. In this case, four-channel Fano resonances with considerable performances are obtained. The proposed structure is analyzed by the coupled mode theory and the finite difference time domain method. It is believed this device can be used as a chip-scale refractive index sensor and optical filter.

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El-Riffaey, Hatem H., and Diaa A. M. Khalil. "Rigorous modal analysis of multi-mode interference (MMI) structures by radiation spectrum method with multiple reflection." Optics Communications 144, no. 4-6 (December 1997): 306–14. http://dx.doi.org/10.1016/s0030-4018(97)00385-4.

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Borhani, Seyyed Jamal, Mohammad Amin Honarvar, and Bal S. Virdee. "Quad notched-band UWB BPF based on quintuple-mode resonator." International Journal of Microwave and Wireless Technologies 9, no. 7 (June 27, 2017): 1433–39. http://dx.doi.org/10.1017/s1759078716001112.

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The design of a novel microstrip ultra-wideband (UWB) bandpass filter with quad narrow notched-band functionality is presented. The filter consists of a multi-mode resonator (MMR) constituted from two modified stepped-impedance stubs that generate six resonate modes, five of which are within the UWB passband where the sixth mode is used to extend the upper stopband of the filter. Two transmission zeroes are located at the 3-dB edge of the passband to enhance the filter's selectivity with a skirt factor of 0.955. The MMR is fed through asymmetric interdigital coupled-lines feed to produce controllable notched-band. Additional notched-bands are generated with a parasitic coupled line. The notched-bands are centered exactly to eliminate interference at 5.2 GHz (wireless local area network (WLAN)), 5.8 GHz (WLAN), 6.8 GHz (radio-frequency identification), and 8 GHz (X-band). Good agreement is obtained between simulation and measurement results. The highly compact filter has dimensions of 8.0 × 9.83 mm2.

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Yan, Xiaohu, Yihang Cao, Yijun Yang, and Yongxiang Yao. "Multi-Modal Image Registration Based on Phase Exponent Differences of the Gaussian Pyramid." Remote Sensing 15, no. 24 (December 17, 2023): 5764. http://dx.doi.org/10.3390/rs15245764.

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In multi-modal images (MMI), the differences in their imaging mechanisms lead to large signal-to-noise ratio differences, which means that the matching of geometric invariance and the matching accuracy of the matching algorithms often cannot be balanced. Therefore, how to weaken the signal-to-noise interference of MMI, maintain good scale and rotation invariance, and obtain high-precision matching correspondences becomes a challenge for multimodal remote sensing image matching. Based on this, a lightweight MMI alignment of the phase exponent of the differences in the Gaussian pyramid (PEDoG) is proposed, which takes into account the phase exponent differences of the Gaussian pyramid with normalized filtration, i.e., it achieves the high-precision identification of matching correspondences points while maintaining the geometric invariance of multi-modal matching. The proposed PEDoG method consists of three main parts, introducing the phase consistency model into the differential Gaussian pyramid to construct a new phase index. Then, three types of MMI (multi-temporal image, infrared–optical image, and map–optical image) are selected as the experimental datasets and compared with the advanced matching methods, and the results show that the NCM (number of correct matches) of the PEDoG method displays a minimum improvement of 3.3 times compared with the other methods, and the average RMSE (root mean square error) is 1.69 pixels, which is the lowest value among all the matching methods. Finally, the alignment results of the image are shown in the tessellated mosaic mode, which shows that the feature edges of the image are connected consistently without interlacing and artifacts. It can be seen that the proposed PEDoG method can realize high-precision alignment while taking geometric invariance into account.

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Bahrami, Ali, Shahram Mohammadnejad, and Ali Rostami. "All-Optical Multi-Mode Interference Switch Using Non-Linear Directional Coupler as a Passive Phase Shifter." Fiber and Integrated Optics 30, no. 3 (June 3, 2011): 139–50. http://dx.doi.org/10.1080/01468030.2011.576379.

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Calò, Giovanna, Gaetano Bellanca, Franco Fuschini, Marina Barbiroli, Davide Bertozzi, Velio Tralli, and Vincenzo Petruzzelli. "4 × 4 Integrated Switches Based on On-Chip Wireless Connection through Optical Phased Arrays." Photonics 10, no. 4 (March 25, 2023): 367. http://dx.doi.org/10.3390/photonics10040367.

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Optical Wireless Networks on-Chip are an emerging technology recently proposed to improve the interconnection between different processing units in densely integrated computing architectures. In this work, we propose a 4 × 4 optical wireless switch (OWS) based on optical phased arrays (OPAs) for broadband reconfigurable on-chip communication. The OPA and OWS design criteria are reported. Moreover, the performances of the OWS are analyzed and optimized considering the electromagnetic propagation in on-chip multilayer structures, with different thicknesses of the cladding layer. The effect on the OWS behavior of a non-ideal distribution of the power in input to the OPA is also investigated by designing a 1 × 7 beam splitter, based on a single-stage multi-mode interference (MMI) device to be used as a single element of the OWS. Then, the MMI output signals are considered in input to the transmitting OPAs and the OWS performances are evaluated.

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Xu, Ronghui, Chengran Ke, Yipu Xue, Yifei Xu, Minmin Xue, Jingfu Ye, Houquan Liu, Ming Chen, Shiliang Qu, and Libo Yuan. "Simultaneous Measurement of Refractive Index and Temperature Based on SMF–HCF–FCF–HCF–SMF Fiber Structure." Sensors 22, no. 22 (November 17, 2022): 8897. http://dx.doi.org/10.3390/s22228897.

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In this research, we proposed and experimentally verified a compact all-fiber sensor that can measure refractive index (RI) and temperature simultaneously. Two segments of hollow-core fiber (HCF) are connected to the two ends of the four-core fiber (FCF) as a beam splitter and a coupler, and then spliced with two sections of single-mode fibers (lead-in and lead-out SMF), respectively. The two hollow-core fibers can excite the higher-order modes of the four-core fiber and recouple the core modes and higher-order modes into the outgoing single-mode fiber, thereby forming inter-mode interference. The different response sensitivities of two interference dips to RI and temperature manifest that the proposed structure can achieve simultaneous measurement. From the experimental results, it can be seen that the maximum sensitivity of the sensor to RI and temperature is 275.30 nm/RIU and 94.4 pm/°C, respectively. When the wavelength resolution is 0.02 nm, the RI and temperature resolutions of the sensor are 7.74 × 10−5 RIU and 0.335 °C. The proposed dual-parameter optical sensor has the advantages of high sensitivities, good repeatability, simple fabrication, and structure. In addition, it has potential application value in multi-parameter simultaneous measurement.

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He, Xianwen, Gaoqi Dou, and Jun Gao. "Individual Channel Estimation in a Diamond Relay Network Using Relay-Assisted Training." International Journal of Digital Multimedia Broadcasting 2017 (2017): 1–8. http://dx.doi.org/10.1155/2017/1320689.

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We consider the training design and channel estimation in the amplify-and-forward (AF) diamond relay network. Our strategy is to transmit the source training in time-multiplexing (TM) mode while each relay node superimposes its own relay training over the amplified received data signal without bandwidth expansion. The principal challenge is to obtain accurate channel state information (CSI) of second-hop link due to the multiaccess interference (MAI) and cooperative data interference (CDI). To maintain the orthogonality between data and training, a modified relay-assisted training scheme is proposed to migrate the CDI, where some of the cooperative data at the relay are discarded to accommodate relay training. Meanwhile, a couple of optimal zero-correlation zone (ZCZ) relay-assisted sequences are designed to avoid MAI. At the destination node, the received signals from the two relay nodes are combined to achieve spatial diversity and enhanced data reliability. The simulation results are presented to validate the performance of the proposed schemes.

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Ghazali, Abu Nasar, Jabir Hussain, and Srikanta Pal. "A hybrid surface-to-surface transition-based UWB-BPF with multiple in-band interference suppression." International Journal of Microwave and Wireless Technologies 11, no. 2 (March 2019): 168–74. http://dx.doi.org/10.1017/s1759078719000242.

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AbstractA compact ultra-wideband (UWB) bandpass filter (BPF) based on surface-to-surface transition technology with features of extended stopband and integrated interference mitigation characteristics is proposed. The basic structure consists of a modified multiple-mode resonator (MMR)-based co-planar waveguide in the ground surface and coupled in broadside manner with the microstrip lines on the top surface. Later, two open-circuited stubs are embedded in the feeding lines and two complementary split ring resonators are etched in the MMR to implement multiple in-band transmission zeros so as to circumvent interference. A prototype is fabricated and measured to validate the results obtained in simulation. The proposed UWB-BPF is compact in size with overall dimensions of 17.82 by 11.08 mm2.

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Liu, Shuo, Baichao Liu, Huanlin Lv, Yanfeng Liang, Fangxu Liu, Haoyu Wang, Yang Cong, Xuanchen Li, and Qingxiao Guo. "Design of a 1 × 3 Power Splitter Based on Multimode Interference in a Parabolic-Type Slot-Waveguide Structure." Applied Sciences 14, no. 13 (July 3, 2024): 5829. http://dx.doi.org/10.3390/app14135829.

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Multimode interference (MMI) couplers based on silicon slot-waveguide structures have received widespread attention in recent years. The key issues that need to be addressed are the size and loss of such devices. This study introduces a 1 × 3 silicon-based slot-waveguide multimode interference power splitter. The device uses a gallium-nitride slot-waveguide structure to reduce the length of the coupling region and decrease additional losses. To reduce the width of the coupling region, the multimode interference coupling area is designed with a parabolic-shaped structure. The introduction of a tapered structure between the input/output waveguides and the coupling region improves additional losses and non-uniformity. Furthermore, we conducted an analysis of the fabrication tolerances of the coupling region. In this paper, we use mode solution to simulate the design of the device in the 1550 nm optical wavelength range. The eigenmode expansion method is used to simulate and optimize the parameters of the device. The device is simulated using the eigenmode expansion solver. The simulation results show that the total length of the coupling region for the device is only 4 μm. The normalized transmission of the device is 0.992, and its excess loss and imbalance are 0.036 dB and 0.003 dB, respectively. The proposed power splitter can be applied to integrated optical circuit design, optical sensing, and optical power measurement.

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Yue, Jian, Xiangyi Sun, Chunxue Wang, Sheng Zhang, Lei Han, Jinkai Wang, Zhanchen Cui, Zuosen Shi, Daming Zhang, and Changming Chen. "Triple-layered optical interconnecting integrated waveguide chip based on epoxy cross-linking fluorinated polymer photonic platform." Optics Express 31, no. 12 (May 25, 2023): 19415. http://dx.doi.org/10.1364/oe.489929.

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In this study, a triple-layered optical interconnecting integrated waveguide chip was designed and fabricated using an epoxy cross-linking polymer photonic platform. Fluorinated photopolymers FSU-8 and AF-Z-PC EP were self-synthesized as waveguide cores and cladding materials, respectively. The triple-layered optical interconnecting waveguide device comprised 4 × 4 arrayed waveguide grating (AWG) -based wavelength-selective switching (WSS) arrays, 4 × 4 multi-mode interference (MMI) -cascaded channel-selective switching (CSS) arrays, and 3 × 3 direct-coupling (DC) interlayered switching arrays. The overall optical polymer waveguide module was fabricated by direct UV writing. For the multilayered WSS arrays, the wavelength-shifting sensitivity was ∼0.48 nm/°C. For the multilayered CSS arrays, the average switching time was ∼280 µs, and the maximum power consumption was <30 mW. For interlayered switching arrays, the extinction ratio approximated 15.2 dB. The transmission loss for the triple-layered optical waveguide chip was measured as 10.0–12.1 dB. The flexible multilayered photonic integrated circuits (PIC) can be used in high-density integrated optical interconnecting systems with a large-volume optical information transmission capacity.

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Lee, Junmin, Hyoyoung Kim, Juwon Ham, and Seunghoon Ko. "Robust Touch Screen Readout System to Display Noise Using Multireference Differential Sensing Scheme for Flexible AMOLED Display." Micromachines 13, no. 6 (June 14, 2022): 942. http://dx.doi.org/10.3390/mi13060942.

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This paper presents a front-end architecture for touch screen panel (TSP) readout in a TSP-integrated, ultrathin flexible display to mitigate severe display noise interference, which is an uncommon mode caused by the large panel load of the TSP in the flexible display. The differential sensing method with multireference TSP channels minimized an imbalance of the phase and amplitude of the coupled-display noise interference. In addition, cascaded time-discrete bandpass sampling was employed to enhance the touch sensitivity in the sensing block. Moreover, a rated front-end block could be reconfigured to a differential or single-ended sensing structure, which reused the prefilter capacitors in the differential sensing for offset cancellation in reference capacitance sensing. To further improve the sensitivity, programmable postfiltering was employed on the reference TSP channels. Subsequently, the proposed front-end was implemented in a 350 nm process, wherein it achieved a SNR of 50.5 dB with a scan rate of 200 Hz and attenuated aggravated display noise interference by more than 6.84 dB as compared to the conventional differential sensing method. The designed chip occupied an area of 4.8 mm2 and consumed 17.6 mW from a 3 V supply.

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Ding, Jinghui, Yunping Qi, Yujiao Yuan, Haowen Chen, Weiming Liu, Yingjun Jia, and Xiangxian Wang. "Multiple Fano resonances based on clockwork spring-shaped resonator for refractive index sensing." Physica Scripta 96, no. 12 (December 1, 2021): 125538. http://dx.doi.org/10.1088/1402-4896/ac3fcf.

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Abstract A surface plasmon polarized structure consisting of two metal-insulator-metal (MIM) waveguide coupled with clockwork spring-shaped resonators are constructed in this paper, and its geometric parameters are controlled within a few hundred nanometers. The finite element method (FEM) and multimode interference coupled mode theory (MICMT) are used to simulate and theoretically calculate the optical response of the designed structure. By modifying the structural parameters of the system, the influence on the asymmetry of the Fano resonance line is studied. The changes of the transmission spectra at different refractive indexes are also investigated. Based on this asymmetric resonant line, the sensitivity and FOM* (figure of merit) value of the cavity with different parameters are measured. The sensitivity and FOM* under the best parameters are 1200 nm RIU−1 and 191.6, respectively. The surface plasmon structure proposed and the results in this paper are promising for applications in the field of high-performance sensing and micro-nano optical devices.

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Liu, Pengwei, Shubin Yan, Yifeng Ren, Xiaoyu Zhang, Tingsong Li, Xiushan Wu, Lifang Shen, and Ertian Hua. "A MIM Waveguide Structure of a High-Performance Refractive Index and Temperature Sensor Based on Fano Resonance." Applied Sciences 11, no. 22 (November 11, 2021): 10629. http://dx.doi.org/10.3390/app112210629.

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A plasmonic refractive index nanosensor structure consisting of a metal-insulator-metal (MIM) waveguide with two symmetrical rectangle baffles coupled with a connected-concentric-double rings resonator (CCDRR) is presented. In this study, its transmission characteristics were investigated using the finite element method (FEM). The consequences, studied via simulation, revealed that the transmission spectrum of the system presents a sharp asymmetric Fano profile due to the destructive interference between the wide-band mode of two rectangle baffles on the bus waveguide and the narrow-band mode of the CCDRR. The effects of the geometric parameters of the structure on the transmission characteristics were investigated comprehensively. A sensitivity of 2260 nm/RIU and figure of merit (FOM) of 56.5 were the best levels of performance that the designed structure could achieve. In addition, the system could act as a sensor for use for temperature sensing, with a sensitivity that could reach 1.48 nm/°C. The designed structure advances with technology with new detection positions and has good application prospects in other high-sensitivity nanosensor fields, for example, acting as a biosensor to detect the hemoglobin level in the blood.

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Wang, Qiong, Zhengbiao Ouyang, Qiang Liu, and Mi Lin. "Densely Distributed Multiple Resonance Modes in a Fan-Shaped Plasmonic Nanostructure Demonstrated by FEM Simulations." Nanomaterials 9, no. 7 (July 4, 2019): 975. http://dx.doi.org/10.3390/nano9070975.

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Multiple resonance modes have important applications since they can provide multi-frequency operation for devices and bring great flexibility in practice. In this paper, based on a fan-shaped cavity coupled to a metal-isolator-metal (MIM) waveguide, a new kind of ultracompact plasmonic nanostructure is proposed to realize multiple resonance modes with dense distribution in a broad spectral range, and demonstrated through finite-element method (FEM) simulations. As many as ten resonance modes with an average interval of about 30 nm are obtained. They originate from the coexistence and interference of three types of basic modes in the fan-shaped cavity, i.e., the ring-waveguide modes, the modes in a ring array of periodic air grooves, and the metal-core-cavity modes. The dependence of resonance modes on structure parameters is investigated, which can provide an effective guide for choosing appropriate multiple-resonance-mode structures. Furthermore, by means of adjusting the geometrical asymmetry induced by the axial offset of the metal core in the fan-shaped cavity, the resonance modes can be effectively modulated, and some new modes appear because the wave path in the cavity is changed. The result proposes a novel way to create multiple resonance modes in plasmonic nanostructures, providing additional degrees of freedom for tailoring the resonance spectra and promising applications in various plasmonic devices, such as optical filters, ultrafast switches, biochemical sensors, and data storages.

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Nicolini, Giovanni, Alessandro Fava, Francesco Centurelli, and Giuseppe Scotti. "A 0.064 mm2 16-Channel In-Pixel Neural Front End with Improved System Common-Mode Rejection Exploiting a Current-Mode Summing Approach." Journal of Low Power Electronics and Applications 14, no. 3 (July 13, 2024): 38. http://dx.doi.org/10.3390/jlpea14030038.

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In this work, we introduce the design of a 16-channel in-pixel neural analog front end that employs a current-based summing approach to establish a common-mode feedback loop. The primary aim of this novel structure is to enhance both the system common-mode rejection ratio (SCMRR) and the common-mode interference (CMI) range. Compared to more conventional designs, the proposed front end utilizes DC-coupled inverter-based main amplifiers, which significantly reduce the occupied on-chip area. Additionally, the current-based implementation of the CMFB loop obviates the need for voltage buffers, replacing them with simple common-gate transistors, which, in turn, decreases both area occupancy and power consumption. The proposed architecture is further examined from an analytical standpoint, providing a comprehensive evaluation through design equations of its performance in terms of gain, common-mode rejection, and noise power. A 50 μm × 65 μm compact layout of the pixel amplifiers that make up the recording channels of the front end was designed using a 180 nm CMOS process. Simulations conducted in Cadence Virtuoso reveal an SCMRR of 80.5 dB and a PSRR of 72.58 dB, with a differential gain of 44 dB and a bandwidth that fully encompasses the frequency range of the bio-signals that can be theoretically captured by the neural probe. The noise integrated in the range between 1 Hz and 7.5 kHz results in an input-referred noise (IRN) of 4.04 μVrms. Power consumption is also tested, with a measured value of 3.77 μW per channel, corresponding to an overall consumption of about 60 μW. To test its robustness with respect to PVT and mismatch variations, the front end is evaluated through extensive parametric simulations and Monte Carlo simulations, revealing favorable results.

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Qi, Yunping, Qilong Wu, Mingrui Su, Hao Li, and Xiangxian Wang. "MIM waveguide refractive index sensor with graphene enhanced three-ring nested resonator Fano resonance." Physica Scripta 99, no. 7 (June 14, 2024): 075525. http://dx.doi.org/10.1088/1402-4896/ad514b.

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Abstract In this paper, a metal-insulator-metal (MIM) waveguide featuring a three-ring nested cavity structure is proposed. We enhance and optimize this design by integrating graphene nanostructures into the ferrule resonance cavity, resulting in a hybrid graphene-MIM waveguide structure. The transmission spectra and electric fields generated by the structure are analyzed by using the finite element method (FEM), shedding light on the formation mechanism of various Fano resonance peaks. The validity of our theoretical analysis is confirmed using multimode interference coupled mode theory (MICMT), and the simulation results are largely aligning with the theoretical verification results. Next, by manipulating the chemical potential of graphene, the Fano resonance can be tuned across a wide range of wavelength bands. And this capability enables the realization of a dynamically tunable refractive index sensor for transmission spectroscopy. Under optimized parameter settings, the refractive index sensor achieves a maximum sensitivity of 1266.67 nm / RIU , and a maximum figure of merit (FOM) value of 199.67 RIU − 1 . Compared with conventional MIM waveguide devices, this design overcomes the difficulty of conventional MIM waveguide structures that cannot be dynamically tunable. Notably, the wavelength of the Fano resonance formed by the transmission spectrum can be dramatically altered when the refractive index of the medium in the surrounding environment is slightly changed. Therefore, this structure expands the repertoire of integrated optical devices with potential applications, particularly in the field of optical sensors.

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Yan, Shubin, Pengwei Liu, Zhanbo Chen, Jilai Liu, Lifang Shen, Xiaoyu Zhang, Jiaming Cui, Tingsong Li, Yang Cui, and Yifeng Ren. "High-Property Refractive Index and Bio-Sensing Dual-Purpose Sensor Based on SPPs." Micromachines 13, no. 6 (May 29, 2022): 846. http://dx.doi.org/10.3390/mi13060846.

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A high-property plasma resonance-sensor structure consisting of two metal-insulator-metal (MIM) waveguides coupled with a transverse ladder-shaped nano-cavity (TLSNC) is designed based on surface plasmon polaritons. Its transmission characteristics are analyzed using multimode interference coupling mode theory (MICMT), and are simulated using finite element analysis (FEA). Meanwhile, the influence of different structural arguments on the performance of the structure is investigated. This study shows that the system presents four high-quality formants in the transmission spectrum. The highest sensitivity is 3000 nm/RIU with a high FOM* of 9.7 × 105. In addition, the proposed structure could act as a biosensor to detect the concentrations of sodium ions (Na+), potassium ions (K+), and the glucose solution with maximum sensitivities of 0.45, 0.625 and 5.5 nm/mgdL−1, respectively. Compared with other structures, the designed system has the advantages of a simple construction, a wide working band range, high reliability and easy nano-scale integration, providing a high-performance cavity choice for refractive index sensing and biosensing devices based on surface plasmons.

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Redouane, Berber, Bouasria Fatima, Chetioui Mohammed, Damou Mehdi, and Boudkhil Abdelhakim. "A High Performance Hybrid Two Dimensional Spectral/Spatial NZCC/MD Code for SAC-OCDMA Systems with SDD Detection." International journal of Computer Networks & Communications 14, no. 02 (March 31, 2022): 61–75. http://dx.doi.org/10.5121/ijcnc.2022.14204.

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This paper proposes a new technique to construct a hybrid zero cross-correlation (NZCC) based on multiple diagonal (MD) code for two-dimensional (2D) spectral amplitude coding for optical code division multiple access code division multiple access (SAC-OCDMA) systems. The proposed hybrid code eliminates totally the multiple access interference (MAI) between a large number of users and allows them to connect simultaneously via the optical communication link with a high speed to receive huge data and serve various areas such as Internet, telephony, DAB radio, digital audio broadcasting, and DVB video. Simulation results demonstrate that the performance of such a SAC-OCDA system based on novel 2D hybrid NZCC/MD code can be easily improved keeping a less complex structure using couplers for direct spectral/spatial dimension (SDD) detection and show superior bit error rate (BER) values comparing to previously developed two-dimensional codes including perfect difference (2D-PD), diagonal Eigen-value units (2D-DEU), multi-service (2D-MS) and balanced incomplete block design (2D-BIBD) codes.

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Chen, Yutai, Huan Chen, Hansi Ma, Zhaojian Zhang, Wanlin Xie, Xin Li, Jian Chen, and Junbo Yang. "On-Chip Optical Adder and Differential-Equation-Solver Based on Fourier Optics and Metasurface." Nanomaterials 12, no. 19 (September 30, 2022): 3438. http://dx.doi.org/10.3390/nano12193438.

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Analog optical computing (AOC) has attracted great attention over the past few years, because of its ultra-high speed (potential for real-time processing), ultra-low power consumption, and parallel processing capabilities. In this article, we design an adder and an ordinary differential equation solver (ODE) on chip by Fourier optics and metasurface techniques. The device uses the 4f system consisting of two metalenses on both sides and one middle metasurface (MMS) as the basic structure. The MMS that performs the computing is the core of the device and can be designed for different applications, i.e., the adder and ODE solver in this article. For the adder, through the comparison of the two input and output signals, the effect of the addition can be clearly displayed. For the ODE solver, as a proof-of-concept demonstration, a representative optical signal is well integrated into the desired output distribution. The simulation result fits well with the theoretical expectation, and the similarity coefficient is 98.28%. This solution has the potential to realize more complex and high-speed artificial intelligence computing. Meanwhile, based on the direct-binary-search (DBS) algorithm, we design a signal generator that can achieve power splitting with the phase difference of π between the two output waveguides. The signal generator with the insertion loss of −1.43 dB has an ultra-compact footprint of 3.6 μm× 3.6 μm. It can generate a kind of input signal for experimental verification to replace the hundreds of micrometers of signal generator composed of a multi-mode interference (MMI) combination used in the verification of this type of device in the past.

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Li, Mengyuan, Lan Rao, Xiaoying He, Feng Tian, Xiaolong Pan, and Xiangjun Xin. "Low-loss, broadband MMI coupler based on thin film lithium niobate platform." Physica Scripta, January 27, 2023. http://dx.doi.org/10.1088/1402-4896/acb6bf.

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Abstract A low-loss broadband power splitter based on X-cut lithium niobate is proposed by utilizing the multimode interference coupler with a shallow-etched slot, wedge-shaped structure and SiO2 cladding. The multimode waveguide with a shallow-etch slot could reduce the sensitivity of multi-mode region on the wavelength and reach to high-quality imaging requirements. Results show that there is an excess loss around 0.01 dB at the operation wavelength of 1550 nm, a broad operation bandwidth of ~ 1314 nm and large tolerance in the shallow-etching. Additionally, our proposed device has been compared with the published and conventional multimode interference coupler for presenting good low-loss and broad bandwidth.

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Shoda, Keiichiro, He Xiao, koudu keiichirou, Haisong Jiang, and Kiichi HAMAMOTO. "Equal input, compact optical power coupler based on nano-pixel structure designed with machine learning." Japanese Journal of Applied Physics, April 14, 2022. http://dx.doi.org/10.35848/1347-4065/ac678d.

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Abstract Multi-mode interference (MMI) waveguide has been widely researched and developed to realize optical power coupler. MMI coupler exhibits superior performance of the “Equal intensity coupling” characteristics, however, it has a problem that excess loss occurs if the phase matching condition is not satisfied at all of the input-ports. The phase condition depends on the number of input-ports, and relatively complicated phase-control is required, thus, it is desired to realize an optical power coupler without complicated phase adjustment. In order to avoid the phase-control difficulty, nano-pixel power coupler is investigated in this paper. Nano-pixel based coupler has a merit of ultra-compact dimension which is close to the wavelength order, therefore, it is expected that less excess-loss even under simple “equal” phase conditions. The structure was examined using FDTD and the simulated results show equal input (intensity and phase) coupling capabilities with a low excess loss of 0.11 dB.

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Aikawa, Yohei, and Hiroyuki Uenohara. "High‐contrast QPSK pattern recognition device consisting of a 4×$\times$4 MMI coupler." Electronics Letters 60, no. 21 (October 28, 2024). http://dx.doi.org/10.1049/ell2.70002.

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AbstractPattern recognition of optical label is utilized not only in packet switches but also in the field of data security due to its wide range of applications. In particular, pattern recognition using waveguide devices is highly valued because it eliminates the need for encoder processing. However, existing methods suffer from the problem of degraded contrast ratio because half of the input power are emitted from non‐target waveguides. In this article, a method is proposed to improve the contrast ratio employing a 44 multi‐mode interference (MMI) coupler with multiple input signals. The theoretical results reveal that the proposed method improves the contrast ratio from 3.0 dB to 9.5 dB and dB for the three‐input and four‐input cases, respectively, for quadrature phase‐shift keying (QPSK)‐modulated signal. Furthermore, numerical simulation was performed through the three dimension finite‐difference time‐domain (3D‐FDTD) method, and the proposed scheme successfully discriminated each QPSK pattern. The power value at all ports closely matches the theoretical value, and the ratios of 9.5 dB and 30.0 dB are numerically obtained.

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Du, Yuhan, Xingchen Ji, Weiqiang Xie, Yu He, Yong Zhang, Meng Tian, and Yikai Su. "High‐Efficiency Fiber‐Chip Edge Coupler for Near‐Ultraviolet Integrated Photonics." Advanced Materials Technologies, May 16, 2024. http://dx.doi.org/10.1002/admt.202400196.

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AbstractIntegrated photonics is demanded in applications operating at ultraviolet to visible wavelengths, such as atomic/quantum systems, on‐chip broadband receivers, and far‐field structured illumination autofluorescence microscopy. A fundamental challenge in these applications is efficient edge coupling from a single‐mode fiber (SMF) to on‐chip photonic components, which is critical for on‐chip integration. In this paper, a high‐efficiency edge coupler based on an alumina‐on‐insulator platform is introduced and experimentally validated. The coupler employs a symmetric double‐tip taper and a multimode interference (MMI)‐based optical combiner. The double‐tip taper effectively expands the mode field diameter at the chip facet to match that of the SMF at the initial stage. Then the MMI‐based combiner efficiently combines the two channels in the taper into a highly confined strip waveguide. A coupling loss of 2.85 dB/facet has been achieved for the transverse magnetic mode at the wavelength of 407 nm, which is the lowest insertion loss for fiber‐chip coupling on this platform to the best of the knowledge. The design can significantly reduce the insertion loss associated with fiber‐chip coupling, offering a key component for diverse areas ranging from atomic/quantum photonic integrated circuits and ultra‐high capacity communications to optical microscopes.

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Journal articles on the topic 'Multi-Mode interference (MMI) coupler'

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