Lateral shearing interferometer for measuring photoinduced refractive index change in As(2)S(3)

We have built and demonstrated a lateral shearing interferometer as a process engineering and control tool for the fabrication and characterization of direct-laser-written waveguide structures in chalcogenide glasses. Photoinduced change in refractive index of 0.154+/-0.002 was measured for as-deposited amorphous As(2)S(3) thin films at 633 nm with an estimated measurement uncertainty of 1.3% for this air-gap interferometer configuration. The simple design of this interferometer can easily be adapted to other wavelengths including mid- and long-wave infrared regions to measure changes in refractive index or material inhomogeneities in transmissive materials.