Development of a mid-infrared refractive index measurement system at cryogenic temperature for the development of an immersion grating to be onboard next-generation infrared space telescope GREX-PLUS

Le résumé fourni par la source

We’re developing an immersion grating made of CdZnTe designed for a high-dispersion mid-infrared spectrograph (10-18 μm, R = λ/Δλ ∼ 30, 000) to be onboard the next-generation infrared space telescope GREX-PLUS. The adoption of an immersion grating will reduce the spectrometer size to 1/n (1/n3 in volume, n: refractive index) compared to conventional diffraction gratings. To determine this absorption coefficient accurately, we need to take the effect of multiple reflection into account that depend on the refractive index. However, the accurate refractive index of CdZnTe (Δn < 10−4) at 10-18 μm below 20 K has not been measured yet. Therefore, we’re developing a measurement system of the refractive index at cryogenic temperatures in the mid-infrared range. We adopt the minimum deviation method in this system to measure the refractive index, measuring the apex and deviation angle of the prismatic sample of material to be measured. Here we give an overview of the measurement system, as well as preliminary results of the refractive index measurement.

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