Tuneable spectrometer for submillimeter astronomy based on silicon Fabry-Perot, preliminary results

Abstract

We are studying and developing high performance spectroscopy solutions in silicon technology in the framework of the instrumental developments around the B-BOP bolometer arrays [1] and in the continuity of the former developments of the Herschel space telescope instruments and in particular its PACS instrument [2]. The integration of multi-wavelength spectroscopic capabilities close to the array of a cooled bolometer would make it possible to detect the interstellar medium (ISM) continuum by scanning and to trace its evolution in particular by the detection of characteristic lines such as the cooling line [CII] at 158µm. In this paper, we present the first concept under development and the preliminary results obtained in our cryogenic optical test bench. This solution is a tunable cavity Fabry-Perot (FP) with silicon mirrors driven by a cryogenic piezoelectric mechanism with a nanometric step. Each mirror is a dielectric Bragg structure, a stack of quarter-wave layers of silicon and air providing a high reflectivity without metal losses. This solution allows extremely accurate scanning around a targeted wavelength. The first prototype is a relatively bulky proof of concept and future optimizations will allow it to be adapted to a focal plane array.