Phase Errors in mid-IR Arrayed Waveguide Gratings based on graded index SiGe-Si technology

TL;DR

This paper introduces a semi-analytical method to analyze phase errors and power truncation in mid-infrared SiGe/Si arrayed waveguide gratings, highlighting the effects of effective index variation and power truncation on device performance.

Contribution

It presents a novel Gaussian approximation and Fourier optics-based model for analyzing phase errors in mid-IR AWGs, linking crosstalk to index deviations and power truncation.

Findings

Power truncation should be kept below 5% for optimal performance.

Effective index variation impacts smaller wavelength AWGs more significantly.

Experimental data shows low relative errors with high crosstalk levels.

Abstract

In this paper, we present a method for analysis of phase errors and power truncation in SiGe/Si graded index arrayed waveguide gratings (AWGs) operating in mid-infrared spectral range. Semi-analytical model used herein is based on Gaussian approximation of the modal field and Fourier Optics. This method is applied to study the correlation between crosstalk level, effective index deviation in array waveguides and power truncation in 3.4 micrometer, 4.5 micrometer, 5.7 micrometer and 7.6 micrometer central wavelength AWGs. We show that the impact of effective index variation is more critical for AWGs with smaller operational wavelengths and power truncation should not exceed 5% for these types of devices. In conclusion, we refer to experimental data of 4.5 {\mu}m, 5.7 {\mu}m and 7.6 {\mu}m central wavelength AWGs where a cross talk level of 24 dB is obtained, corresponding to relative errors of effective indices and equivalent path length deviations respectively lower than 2 10-5 and of 0.2 micrometer in 10 mm length of the devices.