Mid-infrared dispersion relations in InP based photonic crystal slabs revealed by Fourier-transform angle-resolved reflection spectroscopy

TL;DR

This paper introduces a high-precision angle-resolved Fourier-transform spectroscopy method to measure mid-infrared dispersion relations in InP-based photonic crystal slabs, enabling better design of mid-infrared photonic devices.

Contribution

It develops a novel angle-resolved measurement technique compatible with Fourier-transform spectrometers for mid-infrared photonic crystals, overcoming detector sensitivity limitations.

Findings

Mapped 2D photonic band structures of InP-based PC slabs.

Identified complex PC modes using polarization selection rules.

Evaluated mode quality factors for device optimization.

Abstract

Photonic crystals (PCs) offer unique ways to control light-matter interactions. The measurement of dispersion relations is a fundamental prerequisite if we are to create novel functionalities in PC devices. Angle-resolved spectroscopic techniques are commonly used for characterizing PCs that work in the visible and near-infrared regions. However, the techniques cannot be applied to the mid- and long-wavelength infrared regions due to the limited sensitivity of infrared detectors. Here, we propose an alternative approach to measuring infrared dispersion relations. We construct a high-precision angle-resolved setup compatible with a Fourier-transform spectrometer with an angle resolution as high as 0.3 degrees. Hence, the reflection spectra are mapped to the 2D photonic band structures of In(Ga,Al)As/InP based PC slabs, which are designed as mid-infrared PC surface-emitting lasers. We identify complex PC modes with the aid of polarization selection rules derived by the group theory. Spectral analysis makes it possible to evaluate the mode quality (Q) factors. Therefore, angle-resolved reflection is a useful way of optimizing 2D PC parameters for mid-infrared devices.