Serpentine optical phased arrays for scalable integrated photonic lidar beam steering

Abstract

Optical phased arrays (OPAs) implemented in integrated photonic circuits could enable a variety of 3D sensing, imaging, illumination, and ranging applications, and their convergence in new lidar technology. However, current integrated OPA approaches do not scale—in control complexity, power consumption, or optical efficiency—to the large aperture sizes needed to support medium- to long-range lidar. We present the serpentine OPA (SOPA), a new OPA concept that addresses these fundamental challenges and enables architectures that scale up to large apertures. The SOPA is based on a serially interconnected array of low-loss grating waveguides and supports fully passive, 2D wavelength-controlled beam steering. A fundamentally space-efficient design that folds the feed network into the aperture also enables scalable tiling of SOPAs into large apertures with a high fill-factor. We experimentally demonstrate, to the best of our knowledge, the first SOPA using a 1450–1650 nm wavelength sweep to produce 16,500 addressable spots in a 27 × 610 array. We also demonstrate, for the first time, far-field interference of beams from two separate OPAs on a single silicon photonic chip, as an initial step towards long-range computational imaging lidar based on novel active aperture synthesis schemes.

A 2D Pixelated Optical Beam Scanner Controlled by the Laser Wavelength

“…2b-c), where some light is tapped off after each antenna while the waveguide continues to the next grating coupler. The taps can be implemented as (tunable) directional couplers, or the grating coupler can be embedded inside the waveguide and immediately radiate the light off-chip [22], [23], [19]. The snake-like concepts scales much better, as the total waveguide area scales linearly with N x .…”

“…While within a block the phase between antennas is changing as function of wavelengths, the phase between the blocks is different. The distribution can be implemented without phase control between the blocks, and it can be extracted using a calibration routine [23]. Alternatively, as we do it here, we use a balanced splitter tree to connect the input to all the blocks, keeping the inputs of the blocks at the same phase, irrespective of the wavelength.…”

“…(b) Snake, where light is tapped off at fixed distances ∆L. (c) An alternative implementation of Snake[22],[23], where the grating is part of the delay and taps off the light directly. (d) Imbalanced splitter tree, where in each stage m a delay 2 m • ∆L is added in one arm.…”

High-Efficiency, Wide Working Bandwidth Antenna Based on SOI Platform for Optical Phased Array

“…However, the ensuing difficulties are high power consumption and control complexity. A considerable amount of excellent work has been conducted by researchers for these concerns [ 1 , 2 , 3 ]. One approach is to combine beam wavelength modulation in one dimension with phase modulation in the other dimension, thus reducing the number of phase shifters from N 2 to N to achieve reduced power consumption and simplified control.…”

Dispersive OPA at Very Near-Infrared Wavelengths

“…Several integrated OPAs have been recently demonstrated for beam steering, either by wavelength dispersion or active phase control, or a combination of both [2][3]. In this work, we demonstrate a serpentine-based 16-element OPA [4] at very near-IR wavelengths that leverage Silicon Nitride (SiN) waveguide feeding. The 2D calibration-free [5] beam steering has been achieved in the dispersive OPA architecture by just a laser wavelength sweep [6].…”