Cryogenic high-accuracy absolute prism refractometer for infrared through far-ultraviolet optical materials: implementation and initial results

摘要

There currently exists a great void in high quality, cryogenic, infrared (IR) refractive index data, even for the most common IR optical materials. Meanwhile, as the designs of many future refractive IR optical systems and instruments will rely critically on very accurate knowledge of the indices of refraction of their constituent optical components at design operating temperatures, there has been increasing demand for such data within the IR community. We present our progress to date in the design and construction of a Cryogenic, High-Accuracy Refraction Measuring System (CHARMS), which will measure absolute indices of refraction accurate to better than +-1 x 10~(-5). We will operate at wavelengths from 0.105 μm in the far ultraviolet to 20 μm in the mid-IR for sample temperatures ranging from near absolute zero to somewhat above room temperature. Technical challenges, accomplishments, and component developments necessary for successful implementation of the refractometer are discussed. We also present component level accuracy measurements and initial ambient index of refraction measurements for fused silica.