Design of a Low-Crosstalk Sub-Wavelength-Pitch Silicon Waveguide Array for Optical Phased Array

Guangzhu Zhou,Jieyun Wu,Shiwen Yang,Shi-Wei Qu

doi:10.1109/jphot.2021.3103392

Guangzhu Zhou, Jieyun Wu + Show 2 more

Open Access

https://doi.org/10.1109/jphot.2021.3103392

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Abstract

In this work, a compact sub-wavelength-pitch silicon waveguide array with low crosstalk is proposed and analyzed. The crosstalk is suppressed by periodic silicon nano-blocks symmetrically arranged along the silicon strip waveguides. The silicon nano-blocks are properly designed to work in the resonant region as a high-reflection boundary so that the evanescent fields of the silicon waveguide, which directly contribute to the coupling between waveguides, can be truncated. Meanwhile, the nano-blocks periodically perturb the evanescent fields to form a weak-radiating grating, leading to a millimeter-long effective radiation length required for highly directive optical phased arrays. Simulation results show that the crosstalk between the waveguides in the proposed design is at least 10 dB lower than traditional waveguide array with identical sizes within the 1500-1590 nm bandwidth. Furthermore, the proposed design achieves an effective radiation length up to 1.47 mm, resulting in a theoretical narrow beam width of 0.052°. Combining both the low crosstalk and the long effective radiating length, our design offers a promising platform for high-performance two-dimensional scanning optical phased array with a large field of view and a narrow beam width.

Highlights

D UE to the rapid development of photonic integrated circuits (PICs), on-chip optical phased arrays (OPAs) have attracted much attention for their rapid and precise beam steering without mechanical actuators
We propose a compact sub-wavelength-pitch silicon waveguide array, where one-dimensional periodic blocks are symmetrically arranged along silicon strip waveguides
Simulation results show that within the 1500 ∼ 1590 nm bandwidth, the crosstalk between the waveguides in the proposed design is at least 10 dB lower than the referenced traditional waveguide array with identical physical parameters

Summary

INTRODUCTION

D UE to the rapid development of photonic integrated circuits (PICs), on-chip optical phased arrays (OPAs) have attracted much attention for their rapid and precise beam steering without mechanical actuators. A sparse optical phased array with a scanning range of 50° is achieved in [12], where the minimum element pitch is 4λ to avoid crosstalk between waveguides and the position of each element is optimized to suppress the grating lobes caused by the large element spacing. In [14], [15], subarrays composed of strip waveguides with different sizes are utilized to suppress the waveguide crosstalk, achieving an ideal half-wavelength element spacing Another type of half-wavelength-pitch silicon waveguide array with low crosstalk is proposed in [16]. For the waveguide array with an element pitch of 1 μm in this design, overall aliasing-free beam steering ranges of 100° can be achieved with the phase modulation method and 19.3° beam steering ranges via wavelength tuning by 113 nm is numerically demonstrated. Our design offers a promising platform for realization of two-dimensional scanning optical phased array with a large field of view and a narrow beam width

Crosstalk Reduction

Radiation Rates and Frequency-Scanning Characteristics

Findings

CONCLUSION