A waveguide grating antenna (WGA) is an important component in optical phased array (OPA) systems featured by all-solid-state configurations for 3D imaging. The high-performance WGAs with dual polarization, easy fabrication, high radiation efficiency, and high angular resolution are desired for OPAs. This paper presents, to our knowledge, a novel polarization-insensitive WGA design capable of supporting both TE and TM modes, featuring a critical feature size exceeding 250 nm. The designed device demonstrates that this grating antenna exhibits similar upward radiation efficiencies (similar to 85% for TE and similar to 80% for TM) and radiation angles at a wavelength of 1550 nm. The experimental results show that grating antenna perturbation strength can be achieved at less than 4.8 & times; 10-4/mu m for both polarizations. The measured beam divergences are 0.01 degrees (TE) and 0.0101 degrees (TM), with a wavelength scanning sensitivity of 0.123 deg/nm. The proposed polarization-insensitive WGA with high performance is compatible with the 3 mu m commercial platform and an OPA system based on the designed WGA has been designed and simulated. (c) 2026 Chinese Laser Press

High-efficiency, low-loss optical power splitters are essential in photonic integrated circuits. Power splitters with arbitrary splitting ratios and polarization insensitivity are crucial in numerous polarization processing circuits. In this work, we demonstrate a power splitter on thick silicon-on-insulator platform. The device design offers ultra-broadband, polarization-insensitive, low insertion loss performance, and an arbitrary splitting ratio. Experimental results show that splitting ratios between 50:50 and 96:4 can be attained across the C-band wavelength. The 50:50 splitting ratio configuration demonstrated an average insertion loss of less than 0.35 dB and a polarization-dependent loss of under 0.1 dB. The polarization-dependent loss of the splitting ratio is below 0.05 dB.

Power splitters are crucial components in optical communication, sensing, and computing, but their size and operational bandwidth remain constrained. An anti-symmetric tapered sub-wavelength grating waveguide (ATSWG)-based power splitter is theoretically and experimentally verified with a bandwidth of 120 nm and a coupling length of 6 μm. For 3-dB power splitters, the insertion loss is less than 0.94 dB. By varying the spacing ratio of the coupled waveguides, the power splitters are able to achieve different designs with spectral ratios such as 90:10, 80:20, 75:25, and 50:50. This remarkable process resilience positions the ATSWG splitter as a promising candidate for high-yield integration.

Thin-film lithium niobate (TFLN)-based photonic integrated circuits (PICs) require grating couplers that are not only efficient but also compact and compatible with standard fabrication processes to ensure optimal device performance. In this work, we present a novel, to our knowledge, design approach to improve the coupling efficiency of lithium niobate grating couplers. A photonic crystal structure is introduced on an ultra-thin silicon substrate to suppress optical leakage, thereby reducing its detrimental effect on coupling performance. Furthermore, a tapered structure is implemented on the TFLN layer to enhance mode matching between the fiber and the waveguide. Three-dimensional finite-difference time-domain simulations demonstrate that, under TE polarization, the proposed design achieves a maximum coupling efficiency of 69% at a central wavelength of 1549 nm, with a 1 dB bandwidth of 30 nm and a 3 dB bandwidth of 97 nm.

The surging demand for AI-driven massive data transmission has rendered optical communication increasingly vital, necessitating smaller devices capable of sub-diffraction-limit operation. Surface plasmons, capable of overcoming the diffraction limit to achieve nanoscale light manipulation, represent a novel approach for producing high-density integrated photonic chips. Here, we demonstrate a novel approach for actively manipulating plasmon generation using asymmetric nanogrooves integrated with the phase-change material Ge2Sb2Te5. The phase transition modulates the coupling of plasmonic fields, which enables tunable directional excitation. By exploiting the contrasting optical properties of Ge2Sb2Te5 in its amorphous and crystalline phases, we demonstrate active multilevel control of SPP launching with a high extinction ratio (ER) contrast, enabling both one-way and two-way nanosecond switching. The one-way switching achieves high ER values of -15.4 dB (on) and -0.42 dB (off), while the two-way switching exhibits an ER of -10.8 dB (rightward) in the amorphous state and an ER of 5.0 dB (leftward) in the crystalline state. The extinction ratio contrast reaches 15 dB, resulting in a modulation efficiency of up to 96.8%. This approach for surface plasmon manipulation paves the way for ultra-compact plasmonic devices, such as modulators and optical switches, advancing the miniaturization of photonic components.

With the explosion of AI, the requirements for system performance of silicon photonic chips are becoming increasingly higher. High-reliability, low-loss edge couplers are very important for the application of silicon photonic chips. It can support longer-distance transmission and reduce the requirements for the optical source's output power. This paper conducts an in-depth study on a high-reliability, low-loss edge coupler. We numerically studied the factors that affect the coupling loss between standard SMF-28 (Ultra single-mode optical fibers) and Si3N4 (Silicon nitride) based edge coupler, and found that the refractive index of the upper cladding oxide is one of the most important factors. By engineering this refractive index, we experimentally demonstrated that ∼ 0.5 dB coupling loss for TE and ∼ 0.7 dB for TM polarization can be achieved across the full O-band (1250-1350 nm). To our knowledge, this result represents one of the lowest coupling losses reported for a solid edge coupler directly interfacing with SMF-28 fiber across the full O-band.

On $3 \mu \mathrm{m}$-SOI platform, we conducted design optimization and performance comparison of thermo-optic phase shifter and variable optical attenuator (VOA) based on P++ doped silicon, aiming to explore the power consumption limit and the impact on polarization-insensitive performance under different power, distance, and etching pattern conditions. These designs do not require special material processing, have negligible loss, and exhibit excellent power consumption stability. The optimized switching power Ppi = 160 mW, and the power consumption of the tunable optical attenuator at 10 dB attenuation is 135 mW, this performance indicator is applicable to both polarization states (TE&TM). Given the wide applications of thermo-optic phase shifters and VOA, the research findings provide an important preliminary exploration foundation for the large-scale integrated photonic integration on the ${3} \mu \mathrm{m}$ SOI platform.

We proposed a subwavelength grating slot waveguide (SWGS) micro-ring resonator integrated with a one-dimensional (1D) photonic crystal, which is fabricated on a silicon-on-insulator (SOI) platform, and demonstrate its applicability in bulk refractive index sensing applications. The design of the SWGS enables the electric field to be mostly confined in the cladding, thereby enhancing the sensing sensitivity. The cosine-type 1D photonic crystal is utilized to open a photonic bandgap in the micro-ring resonance spectrum, breaking the limitation imposed by the free spectral range (FSR) on the sensing dynamic range. Experiment on measuring sodium chloride solutions with different concentrations shows that the bulk refractive index sensitivity of the air-band mode reaches 621 nm/RIU.

We investigated the impact of gamma-rays and proton irradiation on the performance of high-speed modulators by exposing four-channel 4 x 100 Gbps silicon transmitter chips to both of these radiation sources. The results of our studies indicate that the modulators demonstrated exceptional radiation resistance for various combinations of energy-dose exposure to gamma-rays and proton irradiation in terms of the electro-optic modulation rate, extinction ratio, and modulation efficiency. When subjected to a cumulative radiation dose of 25 Mrad(Si) gamma-rays irradiation, the modulation bandwidth decreases from 52 to 31 GHz. Nevertheless, it was mostly restored using a 7 h annealing procedure at a temperature of 100 degrees C. Proton irradiation at different energy levels and fluences did not have significant detrimental effects on the performance of the modulators. Moreover, it did enhance the modulation efficiency at low fluence.

This paper presents an isolated stratified waveguide filter (Isolated-SWF) array as a core component for miniaturized visible-light spectrometers, fabricated in a 150 nm silicon nitride photonic platform. The designed IsolatedSWFs exhibit low mutual correlation in their spectral responses, enabling high-fidelity reconstruction in an underdetermined system where the number of physical measurement channels $(m=16)$ is substantially smaller than the number of spectral sampling points $(n=800)$. Through structural optimization, an average cross-correlation coefficient of 0.513 was achieved across the 200 nm bandwidth, while an end-to-end deep learning network enabled spectral reconstruction fidelity exceeding 0.99 under underdetermined conditions. The proposed system offers a compact, structurally simple solution with compelling potential for high-resolution broadband visible light spectrometers.

The 3 mu m silicon photonic platform is polarization-insensitive, making polarization beam splitting difficult when integrating with other platforms. We have demonstrated a broadband polarization beam splitter (PBS) on a 3-mu m-thick silicon-on-insulator (SOI) platform using an asymmetric Mach-Zehnder interferometer (AMZI) with optimized waveguide geometry. By engineering the phase accumulation contrast between TE and TM modes via the thermo-optic effect, the device achieves polarization splitting across 1525-1585 nm, delivering extinction ratios (ERs) > 10 dB for TE and TM with insertion loss <0.8 dB.

Spectral routing techniques have attracted plenty of research attention for the past decades, as they enable light manipulation in both the frequency domain and the spatial domain, which is crucial for applications in on-chip spectroscopy, optical switching, and modern communications. Here, we demonstrate an ultra-compact asymmetric nanoplasmonic router for communication bands that routes O and C bands to opposite positions. The nanorouter consists of two uneven grooves that create bidirectional scattered optical fields, utilizing the interference between different optical modes inside the grooves. A broadband spectrum exceeding 100 nm and a maximum extinction ratio of 31 dB are achieved, providing new opportunities for nanophotonic color routing solutions and extensions to other areas such as imaging sensors and spectral measurements.

Silicon photonics is considered as the ideal solution for chip-scale solid Frequency Modulated Continuous Wave (FMCW) Light Detection and Ranging (LiDAR). In this paper, a coherent receiver chip, integrating beam splitters, 180-degree mixers, germanium-balanced photodetectors, and an on-chip temperature sensor is presented. Benefiting from the micron-scale silicon photonics platform, the propagation loss of the waveguide is 0.19 dB/cm, and the imbalance of 180-degree mixers is only 0.30 dB at 1550 nm. The 3 dB cut-off frequency of the balanced photodetector reaches 37.3 GHz, and the responsivity is 0.32A considering the coupling loss. An FMCW LiDAR system with the coherent receiver chip is built for ranging and velocity measurement. Ranging of distance at 120 m with the precision of 0.3 m is achieved. The micron-scale silicon photonics platform can also provide the capabilities for multi-channel coherent receivers and monolithic integration of transmitters and receivers, providing another practical approach for solid state FMCW LiDAR system which can be applied to autopilot, medical and other field for their lightweight requirement.

Integration of resonators impacts the utilization of the 3-mu m-thick silicon-on-insulator (SOI) platform in photonics integrated circuits (PICs). We propose an integrated resonator leveraging a deep-etch silicon waveguide. Through the utilization of a tunable coupler based on multimode interferometers (MMIs), the resonator achieves high fabrication tolerance and reconfigurability. In a critical-coupling state, it serves as a filter with an extinction ratio (ER) of 23.5 dB and quality ( Q) factor of 3.1 x 105, operating within the range of 1530-1570 nm. In an extreme over-coupling state, it functions as a large-bandwidth delay line, offering continuous change in delay time of 22 ps, nearly wavelength-independent. This work provides devices to the 3-mu m-thick silicon photonics device library, enriching the potential applications of this technology platform. (c) 2024 Optica Publishing Group

We design, fabricate, and characterize a polarization-insensitivity 8-bit optical tunable delay line (OTDL) on the 3-μm-thick silicon-on-insulator (SOI) platform, employing low-loss waveguide spirals and rapid-calibrated integrated optical switches. The spirals integrate mode converters and Euler bends, have high fabrication tolerance, low wavelength sensitivity, and propagation loss as low as 0.32 dB/cm within 140 nm bandwidth. The 4-cm-length waveguide spiral has polarization dependent loss (PDL) less than 0.3 dB within 140nm bandwidth. OTTDL utilizes optical switches with extinction ratio (ER) of up to 50 dB for path switching. The switch integrated multimode interferences (MMIs), thermo-optic phase shifter and variable optical attenuators (VOAs). VOAs not only enhance the delay signal-to-noise ratio, but also facilitate rapid calibration in OTDLs. With maximum delay time of 3570 ps and resolution of 14 ps, our OTDL holds significant promise for future applications, particularly in the integration of delay line arrays for microwave photon radar systems.

Optical tunable delay lines (OTDLs) which can capture temporal optical signals, and overcome the challenge of halting light are crucial for optical communications and microwave photonics. Here, a rapid-calibration 8-bit OTDL on the 3-µm-thick silicon-on-insulator (SOI) platform consisting of waveguide spirals and integrated optical switches is proposed, achieving a maximum delay time of 3570 ps with a resolution of 14 ps/stage. The large delay is attributed to the spirals of a 3-µm-thick SOI platform featuring a delay efficiency of approximately 11.49 ps/mm, with wavelength-insensitivity transmission loss of 0.32 dB/cm, and the polarization-dependent loss is only 0.075 dB/cm within 140 nm bandwidth. In addition, the optical switches with extinction ratios up to 50 dB. Integrated variable optical attenuators can suppress crosstalk and facilitate rapid calibration for OTDLs. The advantages of OTDLs' large delay time, high signal-to-noise, and rapid calibration make them suitable for optical programmers and microwave photonics radars.

Crosstalk, calibration complexity, and polarization dependence obstacle the precision of optical networks such as microwave photonics beamforming networks (MPBNs). The optical switch presented in this work, boasting high tolerance and polarization insensitivity, utilizes multimode interferometers (MMIs), a thermo-optical phase shifter, and variable optical attenuators (VOAs) on the 3μm-thick silicon-on-insulator (SOI) platform. The switch exhibits extinction ratio (ER) exceeding 32.5 dB within 140 nm bandwidth, with maximum ER of 50 dB, accompanied by 0.4 dB loss, and features switching speed of 16 μs/21μs. In 10-layer networks, the VOA-assist golden-section algorithm enables optimal calibration within 170 iterations, serving as fundamental component for establishing precise optical networks.

In this work, a vertical N-I-P germanium (Ge) photodetector (PD) with a multi-mode waveguide input is presented. The fabricated devices exhibit a low dark current of 10 nA at bias of −1 V, and a high responsivity of exceeding 0.75 A/W over the wavelength range from 1270 to 1350 nm. High-frequency characteristics measurements show that the photodetector has a 3 dB opto-electrical (OE) bandwidth of 23 GHz under −3 V bias, which can be further improved by optimization of the photodetector configuration. A 50 Gb/s clear eye diagram with a non-return-to-zero (NRZ) modulation format is demonstrated. By using a single-mode excitation source, which is used to simulate light coming from the wavelength division multiplexing (WDM) devices, and sweeping its position, it is shown that the multi-mode input photodetector can be utilized in a WDM receiver to achieve both high responsivity and a flat-top passband.