Ultra-Precision Photometry of AR Coatings.

摘要

The configuration of the AFWL Laser Window Test Apparatus (LWTA) has been modified so that ultra-high precision scans can be made to determine the spacial variations in the reflection of anti-reflective (AR) coatings and other low reflection specimens, such as low efficiency gratings for lasers. The LWTA consists of a computer-controlled rastering device used to position specimens with respect to two stationary CO2 laser probing beams -- one for photometry and one for interferometry. Data are gathered and processed by an on-line computer, are presented to the operator, and are written out on magnetic tape for further analysis. Typically, from 500 to 50,000 points are gathered per specimen, depending upon the spacial precision required. This paper addresses a modification to the LWTA photometer in which the measurement of specimen transmission and attenuation has been sacrificed to obtain a 15-fold improvement in the measurement of specimen reflection.