Pushing the Limits of Broadband and High Frequency Metamaterial Silicon Antireflection Coatings

TL;DR

This paper advances silicon lens technology by developing broadband metamaterial antireflection coatings capable of operating at higher frequencies and wider bandwidths, crucial for next-generation CMB and sub-millimeter observatories.

Contribution

It introduces novel design, fabrication, and testing of silicon metamaterial AR coatings with significantly increased bandwidth and high-frequency performance.

Findings

Octave bandwidth coatings with <0.5% reflection

Prototype 4:1 bandwidth coating demonstrated

Optimized coating for 1.4 THz operation

Abstract

Broadband refractive optics realized from high index materials provide compelling design solutions for the next generation of observatories for the Cosmic Microwave Background (CMB), and for sub-millimeter astronomy. In this paper, work is presented which extends the state of the art in silicon lenses with metamaterial antireflection (AR) coatings towards larger bandwidth and higher frequency operation. Examples presented include octave bandwidth coatings with less than $0.5\%$ reflection, a prototype 4:1 bandwidth coating, and a coating optimized for 1.4 THz. For these coatings the detailed design, fabrication and testing processes are described as well as the inherent performance trade offs.