High-efficiency end-fire 3D optical phased array based on a multi-layer Si₃N₄/SiO₂ platform

Abstract

Beam steering device such as optical phased array (OPA) is a key component in applications of solid-state Lidar and wireless communication. The traditional single-layer optical phased array (OPA) results in a significant energy loss due to the substrate leakage caused by the downward coupling from the grating coupler structure. In this work we have investigated a structure based on multi-layers Si 3 N 4 /SiO 2 platform that can form a 3-D OPA to emit the light from the edge of the device with high efficiency, a 2-D converged out-coupling beam will be end-fired to the air. The high efficiency and wide horizontal beam steering are demonstrated numerically, the influence of vertical crosstalk, the delay length, number of waveguide layers, and the fabrication feasibility are also discussed.

Silicon electro-optic micro-modulator fabricated in standard CMOS technology as components for all silicon monolithic integrated optoelectronic systems *

“…Calculations using the refractive index of n = 3.48 for Si, an absorption factor for Si of 0.59 at 650 nm, and internal reflection considerations as the light moves from higher refractive indices to lower refractive indices surface layers, reveals an emission factor of 0.21 for emission from Si to SiO 2 . Calculations using the refractive indices of n = 1.4 for SiO 2 , 2.5 for Si 3 N 4 an absorption factor of 0.3 for Si 3 N 4 layer, and considering 1 µm thickness layers, yield an emission factor of 0.25 for transmission through the SiO 2 and Si 3 N 4 surface layer to ambient air [16]. The Si 3 N 4 layer contributes to an absorption loss of about 0.3.…”

Photonic Integrated Circuits for an Optical Phased Array

“…The advent of 3-D OPA technology (Figure 14) presents a promising avenue to address these challenges [139,[143][144][145][146][147][148]. Unlike traditional 2-D OPAs, which are limited to emitting 1-D converged beams, 3-D OPAs can emit 2-D converged beams through an end-fire array mechanism, offering highly efficient broadband.…”

“…In summary, the transition towards 3-D OPAs signifies a pivotal shift in overcoming the limitations of the current OPA-LiDAR technologies, especially for long-range detection Moreover, the exploration of passive 3-D OPAs offers a simplified fabrication route, while maintaining CMOS compatibility. By employing a multi-waveguide-layer design, these OPAs can produce 2-D converged beams via end-fire emission and enhanced fiberto-chip coupling efficiency [139,[146][147][148]. Innovations such as the shaped region for wavelength-tuned beam steering and aperiodic arrangements to suppress aliasing underscore the potential of passive 3-D OPAs in reducing the manufacturing complexity without necessitating phase shifters on each layer.…”

Perception and Sensing for Autonomous Vehicles Under Adverse Weather Conditions: A Survey

“…Thermal optics tuning is currently the dominant method as the thermo-optic coefficients of the two major materials, Si and SiN, have a difference of over an order of magnitude [30]. Tunability of thermal tuning is somehow limited, whereas wavelength tuning could achieve a tunability of a couple of dozen degrees per 100 nm change around 1550 nm laser wavelength [31]. There are also other cutting-edge beam steering techniques, such as metasurfaces [32], starting to emerge these years.…”