WIDEBAND SPECTRAL DISPERSER MADE OF ZnS FOR EXOPLANET CHARACTERIZATION USING SPACE-BORNE TELESCOPES

Abstract

We present the development of a spectral dispersion device for wideband spectroscopy for which the primary scientific objective is the characterization of transiting exoplanets. The principle of the disperser is simple: a grating is fabricated on the surface of a prism. The direction of the spectral dispersion power of the prism is crossed with the grating. Thus, the prism separates the spectrum into individual orders while the grating produces a spectrum for each order. In this work, ZnS was selected as the material for the cross disperser, which was designed to cover the wavelength region, λ = 0.6-13 µm, with a spectral resolving power, R ≥ 50. A disperser was fabricated, and an evaluation of its surface was conducted. Two spectrometer designs, one adopting ZnS (λ = 0.6-13 µm, R ≥ 300) and the other adopting CdZnTe (λ = 1-23 µm, R ≥ 250), are presented. The spectrometers, each of which has no moving mechanical parts, consist simply of a disperser, a focusing mirror, and a detector.