Reduction of Effective Terahertz Focal Spot Size By Means Of Nested Concentric Parabolic Reflectors

TL;DR

This paper introduces a nested concentric parabolic reflector design that significantly reduces the terahertz focal spot size, enhancing the ability to analyze smaller samples in spectroscopy.

Contribution

The novel nested parabolic reflector design increases terahertz light throughput and reduces focal spot size, enabling smaller sample analysis in terahertz spectroscopy.

Findings

A 15-fold increase in light throughput for a 2 mm aperture.

Effective reduction of the terahertz focal spot size.

Potential to study smaller samples in spectroscopy.

Abstract

An ongoing limitation of terahertz spectroscopy is that the technique is generally limited to the study of relatively large samples of order 4 mm across due to the generally large size of the focal beam spot. We present a nested concentric parabolic reflector design which can reduce the terahertz focal spot size. This parabolic reflector design takes advantage of the feature that reflected rays experience a relative time delay which is the same for all paths. The increase in effective optical path for reflected light is equivalent to the aperture diameter itself. We have shown that the light throughput of an aperture of 2 mm can be increased by a factor 15 as compared to a regular aperture of the same size at low frequencies. This technique can potentially be used to reduce the focal spot size in terahertz spectroscopy and enable the study of smaller samples.