Shujun Liu 1Ruitao Ma 1Zejie Yu 1,2,3Yaocheng Shi 1,2,3,4Daoxin Dai 1,2,3,4,*
Author Affiliations
1 Zhejiang University, College of Optical Science and Engineering, International Research Center for Advanced Photonics, State Key Laboratory for Extreme Photonics and Instrumentation, Hangzhou, China
2 Jiaxing Key Laboratory of Photonic Sensing and Intelligent Imaging, Jiaxing, China
3 Zhejiang University, Jiaxing Research Institute, Intelligent Optics and Photonics Research Center, Jiaxing, China
4 Zhejiang University, Ningbo Research Institute, Ningbo, China
A silicon-based digitally tunable positive/negative dispersion controller (DC) is proposed and realized for the first time using the cascaded bidirectional chirped multimode waveguide gratings (CMWGs), achieving positive and negative dispersion by switching the light propagation direction. A 1 × 2 Mach–Zehnder switch (MZS) and a 2 × 1 MZS are placed before and after to route the light path for realizing positive/negative switching. The device has Q stages of identical bidirectional CMWGs with a binary sequence. Thus the digital tuning is convenient and scalable, and the total dispersion accumulated by all the stages can be tuned digitally from - ( 2Q - 1 ) D0 to ( 2Q - 1 ) D0 with a step of D0 by controlling the switching states of all 2 × 2 MZSs, where D0 is the dispersion provided by a single bidirectional CMWG unit. Finally, a digitally tunable positive/negative DC with Q = 4 is designed and fabricated. These CMWGs are designed with a 4-mm-long grating section, enabling the dispersion D0 of about 4.16 ps / nm in a 20-nm-wide bandwidth. The dispersion is tuned from -61.53 to 63.77 ps / nm by switching all MZSs appropriately, and the corresponding group delay is varied from -1021 to 1037 ps.
silicon photonics dispersion tuning digital tuning multimode waveguide grating 
Advanced Photonics
2023, 5(6): 066005
Author Affiliations
1 Centre for Micro Nano Systems, School of Information Science and Technology (SIST), Fudan University, Shanghai 200433, China
2 Zhangjiang Laboratory, Shanghai 201210, China
The heterogeneous integration of photonic integrated circuits (PICs) with a diverse range of optoelectronic materials has emerged as a transformative approach, propelling photonic chips toward larger scales, superior performance, and advanced integration levels. Notably, two-dimensional (2D) materials, such as graphene, transition metal dichalcogenides (TMDCs), black phosphorus (BP), and hexagonal boron nitride (hBN), exhibit remarkable device performance and integration capabilities, offering promising potential for large-scale implementation in PICs. In this paper, we first present a comprehensive review of recent progress, systematically categorizing the integration of photonic circuits with 2D materials based on their types while also emphasizing their unique advantages. Then, we discuss the integration approaches of 2D materials with PICs. We also summarize the technical challenges in the heterogeneous integration of 2D materials in photonics and envision their immense potential for future applications in PICs.
two-dimensional materials silicon photonics heterogeneous integration photonic integrated circuits 
Chinese Optics Letters
2023, 21(11): 110007
Author Affiliations
1 Zhejiang University, College of Optical Science and Engineering, Center for Optical and Electromagnetic Research, International Research Center for Advanced Photonics, State Key Laboratory for Modern Optical Instrumentation, Hangzhou, China
2 Zhejiang University, Ningbo Research Institute, Ningbo, China
3 Zhejiang University, Jiaxing Research Institute, Intelligent Optics and Photonics Research Center, Jiaxing Key Laboratory of Photonic Sensing and Intelligent Imaging, Jiaxing, China
Dealing with the increase in data workloads and network complexity requires efficient selective manipulation of any channels in hybrid mode-/wavelength-division multiplexing (MDM/WDM) systems. A reconfigurable optical add-drop multiplexer (ROADM) using special modal field redistribution is proposed and demonstrated to enable the selective access of any mode-/wavelength-channels. With the assistance of the subwavelength grating structures, the launched modes are redistributed to be the supermodes localized at different regions of the multimode bus waveguide. Microring resonators are placed at the corresponding side of the bus waveguide to have specific evanescent coupling of the redistributed supermodes, so that any mode-/wavelength-channel can be added/dropped by thermally tuning the resonant wavelength. As an example, a ROADM for the case with three mode-channels is designed with low excess losses of <0.6, 0.7, and 1.3 dB as well as low cross talks of < - 26.3, -28.5, and -39.3 dB for the TE0, TE1, and TE2 modes, respectively, around the central wavelength of 1550 nm. The data transmission of 30 Gbps / channel is also demonstrated successfully. The present ROADM provides a promising route for data switching/routing in hybrid MDM/WDM systems.
reconfigurability hybrid multiplexing subwavelength grating silicon photonics 
Advanced Photonics Nexus
2023, 2(6): 066004
Author Affiliations
1 University of California, Davis, Department of Electrical and Computer Engineering, Davis, California, United States
2 W&WSens Devices, Inc., Los Altos, California, United States
3 University of California, Baskin School of Engineering, Department of Electrical and Computer Engineering, Santa Cruz, California, United States
The photosensitivity of silicon is inherently very low in the visible electromagnetic spectrum, and it drops rapidly beyond 800 nm in near-infrared wavelengths. We have experimentally demonstrated a technique utilizing photon-trapping surface structures to show a prodigious improvement of photoabsorption in 1-μm-thin silicon, surpassing the inherent absorption efficiency of gallium arsenide for a broad spectrum. The photon-trapping structures allow the bending of normally incident light by almost 90 deg to transform into laterally propagating modes along the silicon plane. Consequently, the propagation length of light increases, contributing to more than one order of magnitude improvement in absorption efficiency in photodetectors. This high-absorption phenomenon is explained by finite-difference time-domain analysis, where we show an enhanced photon density of states while substantially reducing the optical group velocity of light compared to silicon without photon-trapping structures, leading to significantly enhanced light–matter interactions. Our simulations also predict an enhanced absorption efficiency of photodetectors designed using 30- and 100-nm silicon thin films that are compatible with CMOS electronics. Despite a very thin absorption layer, such photon-trapping structures can enable high-efficiency and high-speed photodetectors needed in ultrafast computer networks, data communication, and imaging systems, with the potential to revolutionize on-chip logic and optoelectronic integration.
photoabsorption photon trapping group-velocity reduction photodetectors silicon photonics 
Advanced Photonics Nexus
2023, 2(5): 056001
Author Affiliations
1 Zhejiang University, College of Information Science and Electronic Engineering, State Key Laboratory of Modern Optical Instrumentation, Key Laboratory of Micro-Nano Electronics and Smart System of Zhejiang Province, Hangzhou, China
2 Westlake University, School of Engineering, Key Laboratory of 3D Micro/Nano Fabrication and Characterization of Zhejiang Province, Hangzhou, China
3 Institute of Advanced Technology, Westlake Institute for Advanced Study, Hangzhou, China
4 Institute of Microelectronics of the Chinese Academy of Sciences, Beijing, China
5 Peking University, School of Physics, Frontiers Science Center for Nano-optoelectronics, State Key Laboratory for Mesoscopic Physics, Beijing, China
Optical neural networks (ONNs), enabling low latency and high parallel data processing without electromagnetic interference, have become a viable player for fast and energy-efficient processing and calculation to meet the increasing demand for hash rate. Photonic memories employing nonvolatile phase-change materials could achieve zero static power consumption, low thermal cross talk, large-scale, and high-energy-efficient photonic neural networks. Nevertheless, the switching speed and dynamic energy consumption of phase-change material-based photonic memories make them inapplicable for in situ training. Here, by integrating a patch of phase change thin film with a PIN-diode-embedded microring resonator, a bifunctional photonic memory enabling both 5-bit storage and nanoseconds volatile modulation was demonstrated. For the first time, a concept is presented for electrically programmable phase-change material-driven photonic memory integrated with nanosecond modulation to allow fast in situ training and zero static power consumption data processing in ONNs. ONNs with an optical convolution kernel constructed by our photonic memory theoretically achieved an accuracy of predictions higher than 95% when tested by the MNIST handwritten digit database. This provides a feasible solution to constructing large-scale nonvolatile ONNs with high-speed in situ training capability.
phase-change materials optical neural networks photonic memory silicon photonics reconfigurable photonics 
Advanced Photonics
2023, 5(4): 046004
1 上海大学微电子学院,上海 201800
2 中科院上海微系统与信息技术研究所,上海 200050
3 上海微技术工业研究院,上海 201800
针对多输出端口输出光功率的不均匀性问题,文章设计了一种基于绝缘体上硅(SOI)的1×4多模干涉(MMI)耦合器,提出了一种优化其均匀性的新方法。耦合器输入/输出端采用锥形波导,为提升MMI耦合器的均匀性,对输出端锥形波导采用不等宽设计,通过优化,四路输出端口均匀性高达0.007 4 dB,而总的插损仅有0.058 dB。依据该方法最终使得输出端波导的传输常数失配,避免了波导之间的串扰,实现了对MMI耦合器输出端口均匀性的提升。
硅光子学 多模干涉耦合器 均匀性 损耗 silicon photonics multimode interferometric couplers uniformity loss 
2023, 49(3): 53
Author Affiliations
1 Centre for Optical and Electromagnetic Research, State Key Laboratory for Modern Optical Instrumentation, Zhejiang Provincial Key Laboratory for Sensing Technologies, Zhejiang University, Zijingang Campus, Hangzhou 310058, China
2 Imec USA, Nanoelectronics Design Center, Inc., 194 Neocity Way, Kissimmee, FL34744, USA
3 Ningbo Research Institute, Zhejiang University, Ningbo 315100, China
Chip-scale programmable optical signal processors are often used to flexibly manipulate the optical signals for satisfying the demands in various applications, such as lidar, radar, and artificial intelligence. Silicon photonics has unique advantages of ultra-high integration density as well as CMOS compatibility, and thus makes it possible to develop large-scale programmable optical signal processors. The challenge is the high silicon waveguides propagation losses and the high calibration complexity for all tuning elements due to the random phase errors. In this paper, we propose and demonstrate a programmable silicon photonic processor for the first time by introducing low-loss multimode photonic waveguide spirals and low-random-phase-error Mach-Zehnder switches. The present chip-scale programmable silicon photonic processor comprises a 1×4 variable power splitter based on cascaded Mach-Zehnder couplers (MZCs), four Ge/Si photodetectors, four channels of thermally-tunable optical delaylines. Each channel consists of a continuously-tuning phase shifter based on a waveguide spiral with a micro-heater and a digitally-tuning delayline realized with cascaded waveguide-spiral delaylines and MZSs for 5.68 ps time-delay step. Particularly, these waveguide spirals used here are designed to be as wide as 2 μm, enabling an ultralow propagation loss of 0.28 dB/cm. Meanwhile, these MZCs and MZSs are designed with 2-μm-wide arm waveguides, and thus the random phase errors in the MZC/MZS arms are negligible, in which case the calibration for these MZSs/MZCs becomes easy and furthermore the power consumption for compensating the phase errors can be reduced greatly. Finally, this programmable silicon photonic processor is demonstrated successfully to verify a number of distinctively different functionalities, including tunable time-delay, microwave photonic beamforming, arbitrary optical signal filtering, and arbitrary waveform generation.
silicon photonics programmable photonic integrated circuit waveguide delay lines Mach-Zehnder interferometer 
Opto-Electronic Advances
2023, 6(3): 220030
Author Affiliations
VTT Technical Research Centre of Finland Ltd., Espoo, Finland
Photonic integrated circuits (PICs) are expected to play a significant role in the ongoing second quantum revolution, thanks to their stability and scalability. Still, major upgrades are needed for available PIC platforms to meet the demanding requirements of quantum devices. We present a review of our recent progress in upgrading an unconventional silicon photonics platform toward this goal, including ultralow propagation losses, low-fiber coupling losses, integration of superconducting elements, Faraday rotators, fast and efficient detectors, and phase modulators with low-loss and/or low-energy consumption. We show the relevance of our developments and our vision in the main applications of quantum key distribution, to achieve significantly higher key rates and large-scale deployment; and cryogenic quantum computers, to replace electrical connections to the cryostat with optical fibers.
silicon photonics quantum key distribution quantum computers cryogenic photonics superconducting nanowire single-photon detectors quantum technologies superconducting qubits silicon qubits 
Advanced Photonics Nexus
2023, 2(2): 024002
1 上海大学 微电子学院, 上海 201800
2 上海微技术工业研究院, 上海 201800
3 中国科学院上海微系统与信息技术研究所, 上海 200050
在新型掺钪(Sc)氮化铝(Al1-xScxN)集成光学平台上设计了插入损耗低、传输通道谱线平坦的O波段四通道波分(解)复用器, 并提出了优化方法。所设计的器件结构基于级联马赫-曾德尔干涉仪(MZI)滤波器, 结合弯曲波导结构的定向耦合器改善波长敏感度。针对粗波分复用(CWDM)应用的特性, 文章使用粒子群算法(PSO)提升器件性能优化的效率, 通过调整器件结构的设计参数对四路通道的传输谱线质量进行优化。针对0%, 9%, 23%的掺Sc浓度, 设计的解复用器表现出宽达约15.6nm的1-dB带宽和小于0.1dB的插入损耗, 传输谱线呈“盒状”响应, 各通道间串扰均优于-30.6dB。
硅光子学 波分复用 马赫-曾德尔干涉仪 掺钪氮化铝 silicon photonics WDM MZI scandium-doped aluminum nitride 
2023, 44(1): 25
1 重庆邮电大学通信与信息工程学院,重庆 400065
2 上海交通大学区域光纤通信网与新型光通信系统国家重点实验室,上海 200240
大带宽光子滤波器被广泛应用于稀疏波分复用系统中,而在硅基芯片上实现结构紧凑、性能优良的超大带宽滤波器仍然是该领域研究的重点。提出一种基于光栅辅助反向耦合器的超大带宽硅基光子滤波器。利用窄波导更低有效折射率和更分散电场分布的性质,实现了带宽为92.9 nm、器件长度为250.6 μm的超大带宽滤波器。该滤波器具有矩形度高、带宽大、损耗低等优势,能满足稀疏波分复用系统中解复用等需求。
集成光学 稀疏波分复用 硅光子学 滤波器 光子集成电路 integrated optics coarse wavelength division multiplexing silicon photonics filter photonic integrated circuits 
2023, 43(5): 0513002

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