New nonlinear optical microscope and its application to the observation of ferroelectric domain structure

We have constructed a new nonlinear optical device called the SHG microscope. In the microscope, the fundamental wave with λ = 1.06 μm from a Nd:YAG laser enters a specimen and the second harmonic waves emitted from the specimen are collected by the IR objective lens and the two-dimen-sional image is detected by the CCD camera. By using the SHG microscope, we observed several kinds of specimens with inhomogeneous distribution of the nonlinear optical constant. In particular, we succeeded in observing 90° domains in BaTiO3 and a periodically inverted antiparallel ferroelectric domain in LiTaO3 in a nondestructive way. The general method for observing antiparallel ferroelectric domain structure is discussed.