Wavelength-division multiplexing Si photonic crystal beam steering device for high-throughput parallel sensing.

Hiroyuki Ito,Toshihiko Baba,Hiroshi Abe,Tomoki Tatebe

doi:10.1364/oe.26.026145

Abstract

We proposed and demonstrated a wavelength-division multiplexing (WDM) optical beam-steering device consisting of a thermally controlled doubly periodic Si two-dimensional bulk photonic crystal waveguide and coupled microring multiplexers. Beam forming and steering while maintaining a sharp profile is much easier in this device than with optical phased arrays which need the fine phase control. By dividing the range of beam-steering angles into different wavelength channels, it is possible to cover a wide range of angles, even when each angle is small. In this study, we fabricated a device with four wavelength channels, each of which showed beam steering of 4°-5° as a result of heating, resulting in a total of 16°. Two-dimensional steering is also achieved by loading a collimator lens and selecting one waveguide from those arrayed. We evaluated 112 resolution points with four wavelengths and 448 points in total by switching four waveguides. If this WDM concept is introduced into light detection and ranging and the number of wavelengths is increased, it will be possible to increase the sensing throughput, which is usually constrained by the round-trip time of light, by simultaneous parallel operation.

Highlights

Si photonics achieves high-performance optical devices and allows their large-scale photonic integration via a complementary metal oxide semiconductor (CMOS) process
If we apply this to sensors such as light detection and ranging (LiDAR), it is possible to improve the sensing throughput, which is usually constrained by the round-trip time of light, by simultaneous parallel sensing
We proposed and demonstrated a wavelength-division multiplexing (WDM) optical beam-steering device consisting of a thermally controlled doubly periodic Si bulk photonic crystal waveguide (BPCW) and coupled microring MUXs

Summary

Introduction

Si photonics achieves high-performance optical devices and allows their large-scale photonic integration via a complementary metal oxide semiconductor (CMOS) process. This means that, if the number of pixels in the acquired image is, e.g., 100 k, the frame rate of LiDAR cannot exceed 10 fps even if the sensing duration is ignored To solve these problems, we propose and demonstrate here the allocation of different wavelengths to each beam-steering range using wavelength-division multiplexing (WDM). We adopted a doubly periodic two-dimensional (2D) bulk photonic crystal waveguide (BPCW), which acts as a beam-steering device operated by TO heaters without complex tuning. Using the FEM calculation, ΔT = 400 K was estimated for heating at 2.9 W and considering the above index sensitivity, Δθ = 6.8° was expected This heating is not so efficient and fast because the BPCW is wide and heated indirectly from the heaters buried in the SiO2 cladding having a low thermal conductivity.

Measurement

Discussion

Conclusion