Enhancing the spectral response of filled bolometer arrays for submillimeter astronomy

TL;DR

This paper presents a technique to enhance the spectral response of filled bolometer arrays for submillimeter astronomy by adding an anti-reflecting dielectric layer, significantly improving their sensitivity over broad bands.

Contribution

It introduces a novel method of using an anti-reflecting dielectric layer to increase the spectral response of quarter wave cavity bolometer arrays, demonstrated on Herschel PACS bolometers.

Findings

Spectral response improved by a factor of 1.7 in the 450 micron band.

Optimized dielectric layer parameters enhance broad-band sensitivity.

Experimental validation confirms the effectiveness of the technique.

Abstract

The future missions for astrophysical studies in the submillimeter region will need detectors with very high sensitivity and large field of view. Bolometer arrays can fulfill these requirements over a very broad band. We describe a technique that enables bolometer arrays that use quarter wave cavities to have a high spectral response over most of the submillimeter band. This technique is based on the addition on the front of the array of an anti-reflecting dielectric layer. The optimum parameters (layer thickness and distance to the array) are determined by a 2D analytic code. This general principle is applied to the case of the Herschel PACS bolometers (optimized for the 60 - 210 micron band). As an example, we demonstrate experimentally that a PACS array covered by a 138 micron thick silicon layer can improve the spectral response by a factor 1.7 in the 450 micron band.