A Nonuniform Sparse 2-D Large-FOV Optical Phased Array With a Low-Power PWM Drive

Abstract

Integrated optical phased arrays (OPAs) capable of adaptive beamforming and beam steering enable a wide range of applications. For many of these applications, a large scale 2-D OPA with full phase control for each radiating element is essential to achieve a functional low-cost solution. However, the scalability of such OPAs has been hampered by the optical feed distribution difficulties in a planar photonics process, as well as the high power consumption associated with having a large number of phase control units. In this paper, we present a two-chip solution low-power scalable OPA with a nonuniform sparse aperture, providing radiation pattern adjustment and feed distribution feasibility in a CMOS compatible silicon photonics process. The demonstrated OPA with a 128-element aperture achieves the highest reported grating-lobe-free field-of-view (FOV)-tobeamwidth ratio of 16 • /0.8 • , which is equivalent to a 484-element uniform array. This translates to at least 400 resolvable spots, 30 times more than the state-of-the-art 2-D OPAs. Moreover, by utilizing compact phase shifters in a row-column power delivery grid, we reduce the number of required drivers from 144 to 37. A high-swing pulsewidth modulation (PWM) driving circuit featuring breakdown voltage multipliers and soft turnon activation significantly reduces the power consumption of the system. The electronic driver chip and the integrated photonic chip are fabricated on a 65-nm CMOS process and a thick siliconon-insulator (SOI) silicon photonics process, occupying 1.7 mm 2 and 2.08 mm 2 of active area, respectively.

On-chip 2D beam-steering with a liquid-crystal-tunable optical phased array

“…Integrated optical phased arrays (OPAs) [1][2][3][4][5][6][7][8][9][10][11][12][13], inspired by phased-array radars, perform versatile beamsteering, such as random-access pointing and focusing on regions of interest, as well as sequential scanning. They are suitable for applications such as LiDAR [3][4][5][6][7][8][9][10][11][12][13], image projection [3,[14][15][16] and optical communication [12,17,18]. In contrast to mechanical scanning, OPAs have the additional advantage of being compact and capable of high-speed response, allowing their functionality to be adapted to other systems such as 2D image sensors.…”

“…While 1D-OPAs allow wide-angle beam steering in one-dimension, scanning in the second dimension has been usually achieved with widely tunable lasers [5][6][7][8][9]13]. Single wavelength beam-steering in two-dimensions is naturally achieved by 2D-OPAs with a variable phase in each pixel [2,3,12]. However, such an approach requires the enormous numbers of phase shifters, thereby signi cantly increasing the system complexity and power consumption.…”

“…The 1D array generates only a few OPA grating-lobes, which could even be completely suppressed by reducing the antenna pitch [4,27], leading to a large power fraction in the main beam. The large antenna pitch used in 2D OPAs means that they suffer severely from a reduction in the main beam power caused by the presence of multiple grating-lobes [2,3,12], which poses challenges for long-range applications. (Fig.…”

Breaking FOV-Aperture Trade-Off With Multi-Mode Nano-Photonic Antennas

“…An integrated nano-photonic antenna is a planar structure fabricated on a chip [1]- [17] which is defined as a transducer that couples the guided mode into the free-space mode and vice versa 1 [4]. In other words, an antenna is an on-chip component that in the transmitter setting is fed with a guided mode and radiates into the free-space, and in the receiver setting, captures the free-space incident wave and couples it into a waveguide (Fig.…”

Plasmonic Nanoantenna Array Design

“…The existing dielectric grating antenna suffers from large footprint and bidirectional radiation, which result in large element spacing and waste of radiation energy of the optical nanoantenna array [14][15][16][17][18]. In a uniform antenna array, the element spacing larger than the operating wavelength will lead to the appearance of grating lobes in the radiation pattern of the antenna array, which will limit the steering range of the optical nanoantenna array.…”