White light interferometer for measuring polarization extinction ratio

A white light interferometer was developed for measuring polarization extinction ratios in proton-exchanged, integrated-optic (IO) chips. Usually, such measurements require expensive strain-free polarization components. The instrument which was developed at United Technologies Research Center measured extinction ratios in excess of 95 dB using only interferometric quality optics. The system used a superluminescent diode operating at 825 nanometers as the illumination source and two interferometers combined in series, a measurement interferometer and an analyzing interferometer. The measurement interferometer relied upon the two axes of polarization in the IO chip having different optical pathlengths and the analyzing interferometer was a modified Mach-Zehnder. Results using this system on the IO chips showed that the extinction ratio was 58 dB.