Mid-infrared sub-wavelength grating mirror design: tolerance and influence of technological constraints

TL;DR

This paper presents the design and analysis of mid-infrared sub-wavelength grating mirrors, focusing on how manufacturing constraints affect their optical performance and robustness, with implications for VCSEL integration.

Contribution

It introduces an optimization-based design method that incorporates technological constraints and evaluates their impact on mirror performance and fabrication tolerance.

Findings

Technological constraints reduce the mirror's optical performance.

More stringent manufacturing control improves robustness.

Design trade-offs between performance and tolerance are identified.

Abstract

High polarization selective Si/SiO2 mid-infrared sub-wavelength grating mirrors with large bandwidth adapted to VCSEL integration are compared. These mirrors have been automatically designed for operation at \lambda = 2.3 $\mu$m by an optimization algorithm which maximizes a specially defined quality factor. Several technological constraints in relation with the grating manufacturing process have been imposed within the optimization algorithm and their impact on the optical properties of the mirror have been evaluated. Furthermore, through the tolerance computation of the different dimensions of the structure, the robustness with respect to fabrication errors has been tested. Finally, it appears that the increase of the optical performances of the mirror imposes a less tolerant design with severer technological constraints resulting in a more stringent control of the manufacturing process.