Design and Fabrication of Robust Hybrid Photonic Crystal Cavities

TL;DR

This paper presents a design methodology for robust hybrid photonic crystal cavities that achieve high quality factors by addressing substrate-mediated losses, enabling improved integration of quantum memories.

Contribution

The authors develop a new design approach for hybrid photonic crystals that accounts for fabrication errors and substrate effects, leading to high-Q GaAs-on-diamond cavities.

Findings

Achieved Q factors approaching 30,000 in experiments.

Designed cavities with enhanced robustness against fabrication errors.

Provided a methodology for substrate loss mitigation in hybrid photonic structures.

Abstract

Heterogeneously integrated hybrid photonic crystal cavities enable strong light-matter interactions with solid-state, optically addressable quantum memories. A key challenge to realizing high quality factor (Q) hybrid photonic crystals is the reduced index contrast on the substrate compared to suspended devices in air. This challenge is particularly acute for color centers in diamond because of diamond's high refractive index, which leads to increased scattering loss into the substrate. Here we develop a design methodology for hybrid photonic crystals utilizing a detailed understanding of substrate-mediated loss, which incorporates sensitivity to fabrication errors as a critical parameter. Using this methodology we design robust, high-Q, GaAs-on-diamond photonic crystal cavities, and by optimizing our fabrication procedure we experimentally realize cavities with Q approaching 30,000 at a resonance wavelength of 955 nm.