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Silicon Photonics|152 Article(s)
High-efficiency tunable lasers hybrid-integrated with silicon photonics at 2.0 μ m
Yuxuan Xie, Corey A. McDonald, Theodore J. Morin, Zhican Zhou, Jonathan Peters, John E. Bowers, and Yating Wan
We present hybrid tunable lasers at 2.0-μm wavelength, seamlessly integrated within silicon photonic circuits for advanced biomedical applications. Leveraging III/V semiconductor materials for gain and silicon ring resonators for tuning, the laser achieves a tuning range of 25 nm, precise adjustments below 0.1 nm, and a side-mode suppression ratio of 40 dB. This advancement contributes to the progress in photonic integrated circuits beyond the telecommunication wavelength range, offering scalable and cost-effective solutions for enhanced spectroscopic systems within the 2.0-μm wavelength range. We present hybrid tunable lasers at 2.0-μm wavelength, seamlessly integrated within silicon photonic circuits for advanced biomedical applications. Leveraging III/V semiconductor materials for gain and silicon ring resonators for tuning, the laser achieves a tuning range of 25 nm, precise adjustments below 0.1 nm, and a side-mode suppression ratio of 40 dB. This advancement contributes to the progress in photonic integrated circuits beyond the telecommunication wavelength range, offering scalable and cost-effective solutions for enhanced spectroscopic systems within the 2.0-μm wavelength range.
Photonics Research
- Publication Date: Feb. 28, 2025
- Vol. 13, Issue 3, 737 (2025)
Silicon photonics convolution accelerator based on coherent chips with sub-1 pJ/MAC power consumption
Ying Zhu, Lu Xu, Xin Hua, Kailai Liu, Yifan Liu, Ming Luo, Jia Liu, Ziyue Dang, Ye Liu, Min Liu, Hongguang Zhang, Daigao Chen, Lei Wang, Xi Xiao, and Shaohua Yu
Artificial intelligence (AI), owing to its substantial computing demands, necessitates computing hardware that offers both high speed and high power efficiency. A silicon photonic integrated circuit shows promise as a hardware solution due to its attributes, including high power efficiency, low latency, large bandwidth, and complementary metal–oxide–semiconductor (CMOS) compatibility. Here, we propose a silicon photonic convolution accelerator (SiPh-CA) and experimentally realize a prototype with sub-integrated coherent transmit–receive optical sub-assemblies (sub-IC-TROSAs). The prototype, compared to a previous IC-TROSA-based convolution accelerator, achieves almost the same performances of 1.024 TOPS/channel and 96.22% inference accuracy when it processes neural networks for image recognition, using half the numbers of the modulators and the drivers with which over 1/3 chip footprint and 37.01% power consumption are reduced. By incorporating a broadcasting scheme based on splitters and combiners, the approach can efficiently process multiple convolutions in parallel, achieving several tera operations per second. This scalability feature allows the SiPh-CA to process complex AI and high-performance computing tasks. Artificial intelligence (AI), owing to its substantial computing demands, necessitates computing hardware that offers both high speed and high power efficiency. A silicon photonic integrated circuit shows promise as a hardware solution due to its attributes, including high power efficiency, low latency, large bandwidth, and complementary metal–oxide–semiconductor (CMOS) compatibility. Here, we propose a silicon photonic convolution accelerator (SiPh-CA) and experimentally realize a prototype with sub-integrated coherent transmit–receive optical sub-assemblies (sub-IC-TROSAs). The prototype, compared to a previous IC-TROSA-based convolution accelerator, achieves almost the same performances of 1.024 TOPS/channel and 96.22% inference accuracy when it processes neural networks for image recognition, using half the numbers of the modulators and the drivers with which over 1/3 chip footprint and 37.01% power consumption are reduced. By incorporating a broadcasting scheme based on splitters and combiners, the approach can efficiently process multiple convolutions in parallel, achieving several tera operations per second. This scalability feature allows the SiPh-CA to process complex AI and high-performance computing tasks.
Photonics Research
- Publication Date: Jan. 31, 2025
- Vol. 13, Issue 2, 497 (2025)
All-optically linearized silicon modulator with ultrahigh SFDR of 131 dB · Hz6/7
Qiang Zhang, Qikai Huang, Penghui Xia, Yan Li, Xingyi Jiang, Shuyue Zhang, Shengyu Fang, Jianyi Yang, and Hui Yu
Integrated high-linearity modulators are crucial for high dynamic-range microwave photonic (MWP) systems. Conventional linearization schemes usually involve the fine tuning of radio-frequency (RF) power distribution, which is rather inconvenient for practical applications and can hardly be implemented on the integrated photonics chip. In this paper, we propose an elegant scheme to linearize a silicon-based modulator in which the active tuning of RF power is eliminated. The device consists of two carrier-depletion-based Mach–Zehnder modulators (MZMs), which are connected in series by a 1×2 thermal optical switch (OS). The OS is used to adjust the ratio between the modulation depths of the two sub-MZMs. Under a proper ratio, the complementary third-order intermodulation distortion (IMD3) of the two sub-MZMs can effectively cancel each other out. The measured spurious-free dynamic ranges for IMD3 are 131, 127, 118, 110, and 109 dB·Hz6/7 at frequencies of 1, 10, 20, 30, and 40 GHz, respectively, which represent the highest linearities ever reached by the integrated modulator chips on all available material platforms. Integrated high-linearity modulators are crucial for high dynamic-range microwave photonic (MWP) systems. Conventional linearization schemes usually involve the fine tuning of radio-frequency (RF) power distribution, which is rather inconvenient for practical applications and can hardly be implemented on the integrated photonics chip. In this paper, we propose an elegant scheme to linearize a silicon-based modulator in which the active tuning of RF power is eliminated. The device consists of two carrier-depletion-based Mach–Zehnder modulators (MZMs), which are connected in series by a 1×2 thermal optical switch (OS). The OS is used to adjust the ratio between the modulation depths of the two sub-MZMs. Under a proper ratio, the complementary third-order intermodulation distortion (IMD3) of the two sub-MZMs can effectively cancel each other out. The measured spurious-free dynamic ranges for IMD3 are 131, 127, 118, 110, and 109 dB·Hz6/7 at frequencies of 1, 10, 20, 30, and 40 GHz, respectively, which represent the highest linearities ever reached by the integrated modulator chips on all available material platforms.
Photonics Research
- Publication Date: Jan. 30, 2025
- Vol. 13, Issue 2, 433 (2025)
Polarization-insensitive silicon intensity modulator with a maximum speed of 224 Gb/s
Zanyun Zhang, Beiju Huang, Qixin Wang, Zilong Chen, Ke Li, Kaixin Zhang, Meixin Li, Hao Jiang, Jiaming Xing, Tianjun Liu, Xiaoqing Lv, and Graham T. Reed
Polarization-insensitive optical modulators allow an external laser to be remotely interconnected by single-mode optical fibers while avoiding polarization controllers, which would be convenient and cost-effective for co-packaged optics, 5G, and future 6G applications. In this article, a polarization-insensitive silicon intensity modulator is proposed and experimentally demonstrated based on two-dimensional centrally symmetric gratings, featuring a low polarization-dependent loss of 0.15 dB in minimum and polarization insensitivity of eye diagrams. The device exhibits a low fiber-to-fiber insertion loss of 9 dB and an electro-optic (EO) bandwidth of 49.8 GHz. A modulation speed of up to 224 Gb/s is also demonstrated. Polarization-insensitive optical modulators allow an external laser to be remotely interconnected by single-mode optical fibers while avoiding polarization controllers, which would be convenient and cost-effective for co-packaged optics, 5G, and future 6G applications. In this article, a polarization-insensitive silicon intensity modulator is proposed and experimentally demonstrated based on two-dimensional centrally symmetric gratings, featuring a low polarization-dependent loss of 0.15 dB in minimum and polarization insensitivity of eye diagrams. The device exhibits a low fiber-to-fiber insertion loss of 9 dB and an electro-optic (EO) bandwidth of 49.8 GHz. A modulation speed of up to 224 Gb/s is also demonstrated.
Photonics Research
- Publication Date: Jan. 09, 2025
- Vol. 13, Issue 2, 274 (2025)
Correction of laser sweeping nonlinearities using ultralow-loss on-chip 7 m spiral resonators
Osama Terra, Warren Jin, Hussein Kotb, Joel Guo, and John E. Bowers
Swept laser interferometry is an extremely powerful solution embedded in several recent technologies such as absolute distance measurement, light detection and ranging (LiDAR), optical frequency domain reflectometry, optical coherence tomography, microresonator characterization, and gas spectroscopy. Nonlinearity in the optical frequency sweeping of tunable lasers is a fatal drawback in gaining the expected outcome from these technologies. Here, we introduce an on-chip, millimeter-scale, 7 m spiral resonator that is made of ultralow-loss Si3N4 to act as a frequency ruler for correction of the tunable lasers sweeping nonlinearities. The sharp 2 MHz frequency lines of the 8.5×107 high-quality factor resonator and the narrow-spaced 25.566 MHz frequency ticks of the 7 m spiral allow unprecedented precision for an on-chip solution to correct the laser sweeping nonlinearity. Accurate measurements of the ruler’s frequency spacing, linewidth, and temperature and wavelength sensitivities of the frequency ticks are performed here to demonstrate the quality of the frequency ruler. In addition, the spiral resonator is implemented in an frequency-modulated continuous-wave LiDAR experiment to demonstrate a potential application of the proposed on-chip frequency ruler. Swept laser interferometry is an extremely powerful solution embedded in several recent technologies such as absolute distance measurement, light detection and ranging (LiDAR), optical frequency domain reflectometry, optical coherence tomography, microresonator characterization, and gas spectroscopy. Nonlinearity in the optical frequency sweeping of tunable lasers is a fatal drawback in gaining the expected outcome from these technologies. Here, we introduce an on-chip, millimeter-scale, 7 m spiral resonator that is made of ultralow-loss Si3N4 to act as a frequency ruler for correction of the tunable lasers sweeping nonlinearities. The sharp 2 MHz frequency lines of the 8.5×107 high-quality factor resonator and the narrow-spaced 25.566 MHz frequency ticks of the 7 m spiral allow unprecedented precision for an on-chip solution to correct the laser sweeping nonlinearity. Accurate measurements of the ruler’s frequency spacing, linewidth, and temperature and wavelength sensitivities of the frequency ticks are performed here to demonstrate the quality of the frequency ruler. In addition, the spiral resonator is implemented in an frequency-modulated continuous-wave LiDAR experiment to demonstrate a potential application of the proposed on-chip frequency ruler.
Photonics Research
- Publication Date: Dec. 16, 2024
- Vol. 13, Issue 1, 40 (2025)
Experimental demonstration of a silicon nanophotonic antenna for far-field broadened optical phased arrays
Shahrzad Khajavi, Jianhao Zhang, Pavel Cheben, Daniele Melati, Jens H. Schmid, Ross Cheriton, Martin Vachon, Shurui Wang, Ahmad Atieh, Carlos Alonso Ramos, and Winnie N. Ye
Optical antennas play a pivotal role in interfacing integrated photonic circuits with free-space systems. Designing antennas for optical phased arrays ideally requires achieving compact antenna apertures, wide radiation angles, and high radiation efficiency all at once, which presents a significant challenge. Here, we experimentally demonstrate a novel ultra-compact silicon grating antenna, utilizing subwavelength grating nanostructures arranged in a transversally interleaved topology to control the antenna radiation pattern. Through near-field phase engineering, we increase the antenna’s far-field beam width beyond the Fraunhofer limit for a given aperture size. The antenna incorporates a single-etch grating and a Bragg reflector implemented on a 300-nm-thick silicon-on-insulator (SOI) platform. Experimental characterizations demonstrate a beam width of 44°×52° with -3.22 dB diffraction efficiency, for an aperture size of 3.4 μm×1.78 μm. Furthermore, to the best of our knowledge, a novel topology of a 2D antenna array is demonstrated for the first time, leveraging evanescently coupled architecture to yield a very compact antenna array. We validated the functionality of our antenna design through its integration into this new 2D array topology. Specifically, we demonstrate a small proof-of-concept two-dimensional optical phased array with 2×4 elements and a wide beam steering range of 19.3º × 39.7º. A path towards scalability and larger-scale integration is also demonstrated on the antenna array of 8×20 elements with a transverse beam steering of 31.4º. Optical antennas play a pivotal role in interfacing integrated photonic circuits with free-space systems. Designing antennas for optical phased arrays ideally requires achieving compact antenna apertures, wide radiation angles, and high radiation efficiency all at once, which presents a significant challenge. Here, we experimentally demonstrate a novel ultra-compact silicon grating antenna, utilizing subwavelength grating nanostructures arranged in a transversally interleaved topology to control the antenna radiation pattern. Through near-field phase engineering, we increase the antenna’s far-field beam width beyond the Fraunhofer limit for a given aperture size. The antenna incorporates a single-etch grating and a Bragg reflector implemented on a 300-nm-thick silicon-on-insulator (SOI) platform. Experimental characterizations demonstrate a beam width of 44°×52° with -3.22 dB diffraction efficiency, for an aperture size of 3.4 μm×1.78 μm. Furthermore, to the best of our knowledge, a novel topology of a 2D antenna array is demonstrated for the first time, leveraging evanescently coupled architecture to yield a very compact antenna array. We validated the functionality of our antenna design through its integration into this new 2D array topology. Specifically, we demonstrate a small proof-of-concept two-dimensional optical phased array with 2×4 elements and a wide beam steering range of 19.3º × 39.7º. A path towards scalability and larger-scale integration is also demonstrated on the antenna array of 8×20 elements with a transverse beam steering of 31.4º.
Photonics Research
- Publication Date: Aug. 29, 2024
- Vol. 12, Issue 9, 1954 (2024)
Integrated photonic fractional convolution accelerator
Kevin Zelaya, and Mohammed-Ali Miri
An integrated photonic circuit architecture to perform a modified-convolution operation based on the discrete fractional Fourier transform (DFrFT) is introduced. This is accomplished by utilizing two nonuniformly coupled waveguide lattices with equally spaced eigenmode spectra, the lengths of which are chosen so that the DFrFT and its inverse operations are achieved. A programmable modulator array is interlaced so that the required fractional convolution operation is performed. Numerical simulations demonstrate that the proposed architecture can effectively perform smoothing and edge detection tasks even for noisy input signals, which is further verified by electromagnetic wave simulations. Notably, mild lattice defects do not jeopardize the architecture performance, showing its resilience to manufacturing errors. An integrated photonic circuit architecture to perform a modified-convolution operation based on the discrete fractional Fourier transform (DFrFT) is introduced. This is accomplished by utilizing two nonuniformly coupled waveguide lattices with equally spaced eigenmode spectra, the lengths of which are chosen so that the DFrFT and its inverse operations are achieved. A programmable modulator array is interlaced so that the required fractional convolution operation is performed. Numerical simulations demonstrate that the proposed architecture can effectively perform smoothing and edge detection tasks even for noisy input signals, which is further verified by electromagnetic wave simulations. Notably, mild lattice defects do not jeopardize the architecture performance, showing its resilience to manufacturing errors.
Photonics Research
- Publication Date: Aug. 01, 2024
- Vol. 12, Issue 8, 1828 (2024)
Photonic crystal-connected bidirectional micro-ring resonator array for duplex mode and wavelength channel (de)multiplexing
Zhiwei Guan, Chaofeng Wang, Chuangxin Xie, Haisheng Wu, Junmin Liu, Huapeng Ye, Dianyuan Fan, Jiangnan Xiao, and Shuqing Chen
The progress of on-chip optical communication relies on integrated multi-dimensional mode (de)multiplexers to enhance communication capacity and establish comprehensive networks. However, existing multi-dimensional (de)multiplexers, involving modes and wavelengths, face limitations due to their reliance on single-directional total internal reflection and multi-level mode conversion based on directional coupling principles. These constraints restrict their potential for full-duplex functionality and highly integrated communication. We solve these problems by introducing a photonic-like crystal-connected bidirectional micro-ring resonator array (PBMRA) and apply it to duplex mode-wavelength multiplexing communication. The directional independence of total internal reflection and the cumulative effect of the subwavelength-scale pillar within the single-level photonic crystal enable bidirectional mode and wavelength multiplexed signals to transmit among multi-pair nodes without interference, improving on-chip integration in single-level mode conversion. As a proof of concept, we fabricated a nine-channel bidirectional multi-dimensional (de)multiplexer, featuring three wavelengths and three TE modes, compactly housed within a footprint of 80 μm×80 μm, which efficiently transmits QPSK-OFDM signals at a rate of 216 Gbit/s, achieving a bit error rate lower than 10-4. Leveraging the co-ring transmission characteristic and the orthogonality of the mode-wavelength channel, this (de)multiplexer also enables a doubling of communication capacity using two physical transmission channels. The progress of on-chip optical communication relies on integrated multi-dimensional mode (de)multiplexers to enhance communication capacity and establish comprehensive networks. However, existing multi-dimensional (de)multiplexers, involving modes and wavelengths, face limitations due to their reliance on single-directional total internal reflection and multi-level mode conversion based on directional coupling principles. These constraints restrict their potential for full-duplex functionality and highly integrated communication. We solve these problems by introducing a photonic-like crystal-connected bidirectional micro-ring resonator array (PBMRA) and apply it to duplex mode-wavelength multiplexing communication. The directional independence of total internal reflection and the cumulative effect of the subwavelength-scale pillar within the single-level photonic crystal enable bidirectional mode and wavelength multiplexed signals to transmit among multi-pair nodes without interference, improving on-chip integration in single-level mode conversion. As a proof of concept, we fabricated a nine-channel bidirectional multi-dimensional (de)multiplexer, featuring three wavelengths and three TE modes, compactly housed within a footprint of 80 μm×80 μm, which efficiently transmits QPSK-OFDM signals at a rate of 216 Gbit/s, achieving a bit error rate lower than 10-4. Leveraging the co-ring transmission characteristic and the orthogonality of the mode-wavelength channel, this (de)multiplexer also enables a doubling of communication capacity using two physical transmission channels.
Photonics Research
- Publication Date: Aug. 01, 2024
- Vol. 12, Issue 8, 1802 (2024)
High-order Autler–Townes splitting in electrically tunable photonic molecules
Yihao Chen, Juntao Duan, Jin Li, Yan Chen, Jiewen Li, Jianan Duan, Xiaochuan Xu, and Jiawei Wang
Whispering gallery mode optical microresonators represent a promising avenue for realizing optical analogs of coherent light–atom interactions, circumventing experimental complexities. All-optical analogs of Autler–Townes splitting have been widely demonstrated, harnessing coupled optical microresonators, also known as photonic molecules, wherein the strong coupling between resonant fields enables energy level splitting. Here, we report the characterizations of Autler–Townes splitting in waveguide-coupled microring dimers featuring mismatched sizes. By exploiting backscattering-induced coupling via Rayleigh and Mie scatterers in individual rings, high-order Autler–Townes splitting has been realized, yielding supermode hybridization in a multi-level system. Upon resonance detuning using an integrated phase shifter, intra-cavity coupling-induced splitting becomes almost indistinguishable at the zero-detuning point where the strong inter-cavity coupling counteracts the imbalance of backscattering strengths in individual rings. Through demonstrations on the maturing silicon photonics platform, our findings establish a framework of electrically tunable photonic molecules for coupling-mediated Autler–Townes splitting, offering promising prospects for on-chip signal generation and processing across classical and quantum regimes. Whispering gallery mode optical microresonators represent a promising avenue for realizing optical analogs of coherent light–atom interactions, circumventing experimental complexities. All-optical analogs of Autler–Townes splitting have been widely demonstrated, harnessing coupled optical microresonators, also known as photonic molecules, wherein the strong coupling between resonant fields enables energy level splitting. Here, we report the characterizations of Autler–Townes splitting in waveguide-coupled microring dimers featuring mismatched sizes. By exploiting backscattering-induced coupling via Rayleigh and Mie scatterers in individual rings, high-order Autler–Townes splitting has been realized, yielding supermode hybridization in a multi-level system. Upon resonance detuning using an integrated phase shifter, intra-cavity coupling-induced splitting becomes almost indistinguishable at the zero-detuning point where the strong inter-cavity coupling counteracts the imbalance of backscattering strengths in individual rings. Through demonstrations on the maturing silicon photonics platform, our findings establish a framework of electrically tunable photonic molecules for coupling-mediated Autler–Townes splitting, offering promising prospects for on-chip signal generation and processing across classical and quantum regimes.
Photonics Research
- Publication Date: Aug. 01, 2024
- Vol. 12, Issue 8, 1794 (2024)
High-performance and wavelength-transplantable on-chip Fourier transform spectrometer using MEMS in-plane reconfiguration
Heng Chen, Hui Zhang, Jing Zhou, Chen Ma, Qian Huang, Hanxing Wang, Qinghua Ren, Nan Wang, Chengkuo Lee, and Yiming Ma
On-chip spectrometers with high compactness and portability enable new applications in scientific research and industrial development. Fourier transform (FT) spectrometers have the potential to realize a high signal-to-noise ratio. Here we propose and demonstrate a generalized design for high-performance on-chip FT spectrometers. The spectrometer is based on the dynamic in-plane reconfiguration of a waveguide coupler enabled by an integrated comb-drive actuator array. The electrostatic actuation intrinsically features ultra-low power consumption. The coupling gap is crucial to the spectral resolution. The in-plane reconfiguration surmounts the lithography accuracy limitation of the coupling gap, boosting the resolution to 0.2 nm for dual spectral spikes over a large bandwidth of 100 nm (1.5–1.6 μm) within a compact footprint of 75 μm×1000 μm. Meanwhile, the in-plane tuning range can be large enough for arbitrary wavelengths to ensure the effectiveness of spectrum reconstruction. As a result, the proposed spectrometer can be easily transplanted to other operation bands by simply scaling the structural parameters. As a proof-of-concept, a mid-infrared spectrometer is further demonstrated with a dual-spike reconstruction resolution of 1.5 nm and a bandwidth of 300 nm (4–4.3 μm). On-chip spectrometers with high compactness and portability enable new applications in scientific research and industrial development. Fourier transform (FT) spectrometers have the potential to realize a high signal-to-noise ratio. Here we propose and demonstrate a generalized design for high-performance on-chip FT spectrometers. The spectrometer is based on the dynamic in-plane reconfiguration of a waveguide coupler enabled by an integrated comb-drive actuator array. The electrostatic actuation intrinsically features ultra-low power consumption. The coupling gap is crucial to the spectral resolution. The in-plane reconfiguration surmounts the lithography accuracy limitation of the coupling gap, boosting the resolution to 0.2 nm for dual spectral spikes over a large bandwidth of 100 nm (1.5–1.6 μm) within a compact footprint of 75 μm×1000 μm. Meanwhile, the in-plane tuning range can be large enough for arbitrary wavelengths to ensure the effectiveness of spectrum reconstruction. As a result, the proposed spectrometer can be easily transplanted to other operation bands by simply scaling the structural parameters. As a proof-of-concept, a mid-infrared spectrometer is further demonstrated with a dual-spike reconstruction resolution of 1.5 nm and a bandwidth of 300 nm (4–4.3 μm).
Photonics Research
- Publication Date: Aug. 01, 2024
- Vol. 12, Issue 8, 1730 (2024)
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