Flat low-loss silicon gradient index lens for millimeter and submillimeter wavelengths

TL;DR

This paper introduces a flat silicon gradient index lens for millimeter and submillimeter wavelengths, designed for low absorption losses and achromatic performance over a wide bandwidth, with promising simulation results.

Contribution

It presents a novel design of a flat silicon GRIN lens with a wide bandwidth and low losses, including simulation and planned fabrication methods.

Findings

Simulated efficiency exceeds that of traditional silicon lenses.

Achromatic performance over a broad bandwidth achieved.

Design suitable for fabrication using DRIE and wafer-bonding.

Abstract

We present the design, simulation, and planned fabrication process of a flat high resistivity silicon gradient index (GRIN) lens for millimeter and submillimeter wavelengths with very low absorption losses. The gradient index is created by subwavelength holes whose size increases with the radius of the lens. The effective refractive index created by the subwavelength holes is constant over a very wide bandwidth, allowing the fabrication of achromatic lenses up to submillimeter wavelengths. The designed GRIN lens was successfully simulated and shows an expected efficiency better than that of a classic silicon plano-concave spherical lens with approximately the same thickness and focal length. Deep reactive ion etching (DRIE) and wafer-bonding of several patterned wafers will be used to realize our first GRIN lens prototype.