Measurement of refractive indices of 20 optical materials at low temperatures

We build a refractometer capable of measuring refractive indices at low temperatures from visible to near-infrared wavelength. Refractive indices of 20 optical materials (three fluorides, 15 glasses, fused silica, and KRS-5) are measured at wavelengths of 365.0, 435.8, 546.1, 1014.0, 1529.6, 2122, and 3298 nm at temperatures of ~80, 120, 180, 240, and 293 K. The temperature dependences of the refractive indices are shown in a table and figures.