Ultrahigh reflectivity photonic crystal membranes with optimal geometry

Published

July 30, 2024

Author(s)

Feng Zhou, Yiliang Bao, Jason Gorman, John R. Lawall

Abstract

Photonic crystal (PhC) structures with subwavelength periods are widely used for diffractive optics, including high reflectivity membranes with nanoscale thickness. Here, we report on a design procedure for 2D PhC silicon nitride membrane mirrors providing optimal crys-tal geometry using simulation results obtained with rigorous coupled-wave analysis. The Downhill Simplex algorithm, a robust numerical approach to finding local extrema of a function of multiple variables, is used to optimize the period and hole radius of PhCs with both hexagonal and square lattices, as the membrane thickness is varied. Following these design principles, nanofabricated PhC membranes made from silicon nitride have been used as input couplers for an optical cavity, resulting in a maximum cavity finesse of 33 000, corresponding to a reflectivity of 0.999 82. The role played by the spot size of the cavity mode on the PhC was investigated, demonstrating the existence of an optimal spot size that agrees well with predictions. We find that, compared to the square lattice, the hexagonal lattice exhibits a spec-trally wider reflective range, less sensitivity to fabrication tolerances, and higher reflectivity for membranes thinner than 200 nm, which may be advantageous in cavity optomechanical experiments. Finally, we find that all of the cavities that we have constructed exhibit well-resolved polarization mode splitting, which we expect is due primarily to a small amount of anisotropic stress in the silicon nitride and PhC asymmetry arising during fabrication.

Citation

Applied Physics Letters Photonics

Volume

9

Pub Type

Journals

Download Paper

https://doi.org/10.1063/5.0204067

Local Download

Keywords

photonic crystal, membrane, silicon nitride, RCWA, Fabry-Perot

Citation

Zhou, F. , Bao, Y. , Gorman, J. and Lawall, J. (2024), Ultrahigh reflectivity photonic crystal membranes with optimal geometry, Applied Physics Letters Photonics, [online], https://doi.org/10.1063/5.0204067, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=956827 (Accessed May 10, 2026)

Additional citation formats