ABSTRACT
Integrated optical phased arrays (OPA) require calibration to account for mismatches amongst the channels. Furthermore, beams emitted from an OPA tend to distort when the chip's temperature changes. We propose to utilize a deep neural network (DNN) to adaptively control the phase modulator voltages of the OPA and create a desired beam pattern in the presence of process mismatches and temperature changes. As a proof of concept, adaptive beam forming was demonstrated with an integrated 128-channel OPA realized in a commercial foundry silicon photonics (SiP) process. Beam forming within 50° field of view (FoV) is demonstrated, while accuracy of 0.025° is achieved when the beam is swept in 0.1° step at a fixed temperature. The DNN is also used to create beams with multiple peaks at desired spatial angles. The DNN is shown to properly adjust the phase modulator voltages to keep the beam nearly intact as temperature changes within 20°C range.
ABSTRACT
A single-photon avalanche diode (SPAD) with enhanced near-infrared (NIR) sensitivity has been developed, based on 0.18 µm CMOS technology, for use in future automotive light detection and ranging (LIDAR) systems. The newly proposed SPAD operating in Geiger mode achieves a high NIR photon detection efficiency (PDE) without compromising the fill factor (FF) and a low breakdown voltage of approximately 20.5 V. These properties are obtained by employing two custom layers that are designed to provide a full-depletion layer with a high electric field profile. Experimental evaluation of the proposed SPAD reveals an FF of 33.1% and a PDE of 19.4% at 870 nm, which is the laser wavelength of our LIDAR system. The dark count rate (DCR) measurements shows that DCR levels of the proposed SPAD have a small effect on the ranging performance, even if the worst DCR (12.7 kcps) SPAD among the test samples is used. Furthermore, with an eye toward vehicle installations, the DCR is measured over a wide temperature range of 25-132 °C. The ranging experiment demonstrates that target distances are successfully measured in the distance range of 50-180 cm.
ABSTRACT
A CMOS light pulse receiver (LPR) cell for spatial optical communications is designed and evaluated by device simulations and a prototype chip implementation. The LPR cell consists of a pinned photodiode and four transistors. It works under sub-threshold region of a MOS transistor and the source terminal voltage which responds to the logarithm of the photo current are read out with a source follower circuit. For finding the position of the light spot on the focal plane, an image pixel array is embedded on the same plane of the LPR cell array. A prototype chip with 640 × 240 image pixels and 640 × 240 LPR cells is implemented with 0.18 µm CMOS technology. A proposed model of the transient response of the LPR cell agrees with the result of the device simulations and measurements. Both imaging at 60 fps and optical communication at the carrier frequency of 1 MHz are successfully performed. The measured signal amplitude and the calculation results of photocurrents show that the spatial optical communication up to 100 m is feasible using a 10 × 10 LED array.
