LASER REFLECTANCE TEST SETUP

The Laser Reflectance test measures the grating period by illuminating a subaperature of the grating under test with a known wavelength and measuring the angles of reflection and diffraction. The period is calculated from a linearized grating equation. A collection of subaperatures across the grating are measured to determine the period uniformity. From this data a contour map of the grating period is formed and kept in the database for grating selection.