Nonlinear Integrated Photonics for Ranging Applications

This thesis explores the application of recent advances in integrated photonics to the field of light detection and ranging (LiDAR). The progress in photonic integration allows for unprecedented levels of light manipulation on micrometer scales through the fabrication of high-confinement, low-loss optical waveguides. In combination with medium nonlinearity, these waveguides enable a plethora of phenomena, one of which is frequency combs. Since their discovery in 2007, microcombs have been used in a wide range of applications, including astronomical spectrometer calibration, chip-scale atomic clocks, optical telecommunications, and microwave synthesis. In this thesis, I investigate new approaches to optical ranging with SiN microresonator frequency combs and novel photonic integrated laser sources.

First, I report on the demonstration of massively parallel coherent ranging enabled by a newly discovered frequency-modulated microcomb. This study solves a longstanding bottleneck of parallel acquisition in frequency-modulated continuous-wave (FMCW) LiDAR community. Owing to a single high coherence frequency agile laser, ranging with 40 parallel independent channels was achieved. The subsequent result highlights the possibilities attained by the convergence of microresonator combs, metrology and optical telecommunications fields. The dual chirped comb implementation, in conjunction with a high-bandwidth telecommunication receiver, resulted in 6 MPix/s imaging rates, which were the fastest demonstrated at that time for coherent LiDAR. Next, by revisiting the foundations of the complex dynamics of nonlinear systems, the chaotic frequency combs were studied in the context of optical ranging. For the first time, it was shown that incoherent combs can be harnessed to utilize their unique chaotic properties, which so far had not been considered before, and to implement random modulation LiDAR. Counter-intuitively, the wide band amplitude and frequency noise allowed the performance comparable to FM microcombs while alleviating the transmitter requirements for modulators and high-speed electronics. Based on the previous discoveries, parallel and inertia-free 3D ranging was presented. The combination of 2D optical disperses with broadband tuning of a noisy microcomb, enabled by integrated microheaters, resulted in fully passive scanning, which had never been demonstrated with frequency combs and is widely required for future LiDAR. Lastly, photonic-electronic integrated LiDAR engine was developed. This result truly highlights the late progress in photonic integration at EPFL and in general. The engine includes: low-noise frequency agile Vernier laser based on \SiN waveguides with integrated piezo actuators and hybrid integrated III-V gain media, Erbium-doped chip-scale optical amplifier, and a high-voltage arbitrary waveform generation circuit using standard CMOS foundry process. Coherent ranging demonstrated with this source paves the way to fully integ