Optimization of Stealthy Hyperuniform Materials for Quantum Cascade Lasers Using Various Geometries

Abstract

Stealthy hyperuniform (SHU) materials are a novel class of metamaterials that combine the band gap properties of photonic crystals with spatial isotropy, enabling applications in optics and photonics such as silicon photonic waveguides, mode selection in THz quantum cascade lasers, tailored light scattering, edge detection, and mid-infrared filtering. These metamaterials often have much smaller or complete photonic band gaps (PBG) compared to their photonic crystal counterparts, without requiring the incoming light to be at normal incidence. A large PBG or gap-to-midgap ratio, balancing the width of the PBG against its central frequency, is desirable for precise control over the propagation of light or electromagnetic waves. This thesis investigated the optimization of PBGs through numerical simulation and experiments using various geometric patterns, including triangles, squares, rectangles, hexagons, circles, ellipses, and crosses. After simulating such patterns on a 1x1 unit cell in MIT Photonic Bands (MPB) software, the optimal geometric patterns were determined to be square, hexagon, and circle. For experimental validation, a circle-based SHU-patterned Indium Phosphide (InP) crystal was fabricated and analyzed using FTIR transmission spectroscopy. Compared to the unpatterned InP crystal, the patterned sample exhibited lower transmission across all mid-IR frequencies and reduced angular dependence, confirming its isotropic properties. Notably, a photonic band gap emerged around the 1000 cm⁻¹ wavenumber. These findings demonstrate the potential of SHU-based geometries in tunable, angle-independent photonic devices for mid-IR applications.