High spatial resolution second-harmonic interferometry

A monolithic compact fully fiber coupled Nd:YAG (yttrium aluminum garnet) continuous wave laser based second-harmonic interferometer with 60 μm spatial resolution is presented. The device is tested by measuring the dispersion of laser etched polymeric films; the result found is a phase shift sensitivity down to 7 × 10−3 rad for an acquisition time as fast as 300 μs. These results demonstrate the feasibility of high spatial resolution second-harmonic interferometry, and an outlook is given for its use as a novel quantitative phase sensitive imaging technique.