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.
Microring resonators (MRRs) are widely used in optical filters due to their compact size, high Q, and narrow linewidth. However, traditional MRR-based high sensitivity sensors suffer from narrow free spectral range (FSR), which limits the number of channels for detecting substances and causes interference with the identification of the center wavelength when the refractive index of analytes changes significantly. In this paper, we propose an ultra-large FSR and high sensitivity filter utilizing subwavelength grating slot microring resonator with inner silicon blocks with different widths, achieving FSR of 95.5 nm and refractive index sensitivity of 743 nm/RIU. And a lab-on-chip system comprised of eight channels-based filters is presented, promoting the development of silicon photonics in the detecting resolution of small refractive index changes of analytes to 3.60×10-4 RIU and multiple analytes simultaneously.
Silicon photonics enables large-scale integration of Frequency Modulated Continuous Wave (FMCW) Light Detection and Ranging (LiDAR) system on silicon on insulator (SOI) substrate. In this paper, we set up an FMCW LiDAR system for a chip-scale coherent receiver chip based on a 3 µm SOI platform which has the advantages of low waveguide loss and high process tolerance. An iterative learning pre-distortion method is used for linear frequency sweep. With the home-built FMCW LiDAR system, we have achieved a detection range of 160 m with an accuracy of 0.3 m which pave the way for miniaturized LiDAR used for autonomous driving.
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