Measurement of the reflectance of the INM cryogenic radiometer cavity at several wavelengths

This article gives the results of the measurements of the Institut National de Metrologie (INM) LaseRad cavity reflectance. These measurements were performed at several laser wavelengths: 325 nm, 488 nm, 514 nm, 543 nm, 633 nm and 1550 nm. The comparison of our measurements at 633 nm with those carried out by Cambridge Research & Instrumentation, Inc. (USA) five years ago shows satisfactory agreement. The discrepancy between these two measurements is within the measurement uncertainties in the range of 5 × 10 -5 . The change in the reflectance with wavelength is not negligible. The reflectance varies from 2.8 × 10 -4 to 1.10 × 10 -4 , according to the wavelength.