Photonic integrated coherent LiDAR engine

Light Detection and Ranging (LiDAR) is a key technology that will be pivotal for navigation both in future autonomous vehicles as well as for drones and in space on satellites. Coherent LiDAR, also known as Frequency Modulated Continuous Wave, is a technique for ultra-long range, high sensitivity ranging that is immune to sunlight and interference from other LiDAR signals and facilitates classification enabled by instantaneous position and velocity information per pixel. Yet, to date, the use of coherent FMCW sources is impeded by the dual laser requirements of frequency agility and narrow linewidth, which makes LiDAR based on multiple parallel laser sources difficult to equate with legacy time of flight LiDAR. At EPFL, we have recently demonstrated a massively parallel soliton based FMCW LiDAR, whose key functionality is on chip, compact and provides a clear path towards full photonic integration.This is a new approach, based on commercially available Si3N4 based nonlinear and ultra-low loss integrated photonics (commercialized via LIGENTEC SA). This approach allows a frequency chirped pump to be faithfully transduced onto dozens of spectral lines of an optical frequency comb, constituting a multichannel FMCW LiDAR engine, while simultaneously providing a path to ultra-compact and fully chip integrated LiDAR engines. This system can be further, and substantially, enhanced leveraging the concepts of dual-comb spectroscopy and multi-heterodyne techniques, where a 2nd FMCW local oscillator comb with slight repetition rate offset would allow simultaneous detection of all LiDAR channels on the high-bandwidth coherent receiver, thus alleviating an array of photodiodes and demultiplexer modules. Further advancements in planning at EPFL are to demonstrate a fully integrated LiDAR engine based on an injection locked DFB laser chip coupled to Si3N4 integrated photonics.