Patent ID: 9261429
Filing Date: 2016-02-16
CPC Classification: G01B,G01J,G01L,G01M,G01N,G02B

Claim Text:
1. A measurement system for measuring at least one mode spectrum of a waveguide formed in a top surface of a substrate and having a depth-of-layer (DOL) of greater than 50 microns, the system comprising: a coupling prism having an input surface, an output surface and a coupling surface, a refractive index n a light source system configured to illuminate the substrate-prism interface through the input surface of the prism, thereby forming reflected light that includes mode lines of the at least one mode spectrum having a first size, wherein the reflected light exits the output surface of the coupling prism; a photodetector system having a detector and arranged to receive the reflected light from the coupling prism and detect the at least one mode spectrum on the detector; and a controller configured to process the detected at least one mode spectrum to correct a distortion of the mode lines caused by refraction of the reflected light at the output surface of the coupling prism to a corrected mode spectrum having a second size; and wherein the coupling prism has a maximum prism angle α