Chip-scale Lidar


The superiority of lidar compared to radio-frequency and ultrasonic solutions in terms of depth and lateral resolution habeen known for decades. In recent years, both application pull such as 3D vision for robotics, rapid prototyping, self-driving cars, and medical diagnosticsas well as technology developments such as integrated optics and tunable lasers have resulted in new activities

Pulsed, amplitude-modulated continuous-wave (AMCW), and frequency-modulated continuous-wave (FMCW) lidars can all be used for ranging. The latter option enables excellent depth resolution at the micron level. Achieving this level of performance is contingent on a precision light source with accurate frequency modulation. This thesis presents a fully integrated solution realizing an electro-optical phase-locked loop (EO-PLL) fabricated on separate complementary metal-oxide-semiconductor (CMOS) and silicon-photonic wafers interconnected with through-silicon vias (TSVs).

The system performs 180,000 range measurements per second, with a root-mean square (RMS) depth precision of 8 μm at distances of ±5cm from the range baseline increasing to 4.2 mm RMS error at a range of 1.4 m, limited by the coherence length of the laser used in these experiments. Optical elements including input light couplers, waveguides, and photodiodes are realized on a 3 mm by 3 mm silicon-photonic chip. The 0.18 μm CMOS application-specific integrated circuit (ASIC) of the same area comprises the front-end trans-impedance amplifier, analog electro-optical PLL, and digital control circuitry consuming 1.7 mA from a 1.8-V supply and 14.1 mA from a 5-V supply. The latter includes 12.5 mA bias current for the distributed Bragg reflector (DBR) section of the tunable laser. Also presented in the thesis is a novel dual mode lidar that combines FMCW and chirped-AMCW operation to simultaneously achieve precision depth resolution and a longer operating range not limited by Laser coherence length.

Behnam Behroozpour Baghmisheh
Publication date: 
January 31, 2017
Publication type: 
Ph.D. Dissertation
Baghmisheh, B. B. (2017). Chip-Scale Lidar. United States: University of California, Berkeley.

*Only registered BSAC Industrial Members may view project materials & publications. Click here to request member-only access.