Development of a cryogenic high precision refractive index measurement system for CdZnTe using the minimum deviation method

We have developed a compact cryogenic system for high precision refractive index measurements of CdZnTe, aimed at supporting the optical design of the GREX PLUS high resolution spectrograph. The system is based on the minimum deviation method and incorporates improved vacuum rotation mechanics, non contact magnetic torque transfer, a low temperature ceramic thrust bearing, and flexible high purity copper thermal links. Together with narrow band mid infrared illumination and liquid nitrogen cooled InSb/MCT detectors using lock in detection, the setup enables stable angle measurements in the 4–20 K temperature range. The achieved accuracy of ∣δn∣<10^(-3) in the 10–18 µm wavelength region meets the requirements for designing high dispersion immersion gratings for space infrared instrumentation.