New method for high-accuracy measurements of the internal transmittance in the deep-ultraviolet spectral region using prism-shaped samples

A method capable of measuring the internal transmittance T_i of fused silica @193 nm with a precision better than 0.01 %/cm (3σ) is presented. The basic idea is to vary the optical pathlength during the measurement within one and the same prism-shaped sample by moving the latter through the optical test beam. In comparison to the standard multiple-sample experiment this greatly relaxes the requirements for the repeatability of surface preparation. Lack of any standards makes it currently impossible to determine the absolute accuracy experimentally. However, calculations indicate that it is very likely within 0.02 %/cm (3σ). The application to materials and wavelengths other than what were chosen here for demonstration is straightforward.