Silicon Photonic FMCW LiDAR Calibration Engine With Optimized On-Chip Delay Lines

This study presents the comprehensive design, optimization, and experimental validation of an advanced silicon photonic delay line tailored for nonlinearity calibration in frequency-modulated continuous-wave (FMCW) LiDAR systems. The novel delay line employs a hybrid architecture combining Archimedes' and Euler's spirals, which significantly minimizes connection loss and higher-order mode crosstalk, resulting in a low-loss, high-density optical path. Fabricated using a standard CMOS multiple project wafer (MPW) process, the delay line achieves 0.24 dB/cm loss and 7.56 ns optical delay within a compact 1 × 3 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> area, representing a substantial 41.5% improvement in delay density over our prior designs. Experimental outcomes validate the engine's capability for nonlinearity calibration, demonstrating a notable enhancement in signal-to-noise ratio and linewidth narrowing post-calibration. This work paves the way for the development of multifunctional, highly integrated FMCW LiDAR optical-electrical engines through the optimization of essential packaging and circuit functionalities.