Spectroellipsometric approach to determine linear electro-optic coefficient of c-axis-oriented LiNbO3 thin films

We present a simple method to determine the linear electro-optic coefficient of thin films with spectroscopic ellipsometry. This technique allows noncontact and nondestructive measurement of the as-grown state of films without the need to fabricate a waveguide. The principle behind this is that the electro-optic effect is regarded as perturbation to the optical parameters. Comparing differences in tanΨ spectra in terms of applied voltage and wavelength yields a change in the effective wavelength of light propagating through a dielectric medium, which is equivalent to electro-optic-induced phase shift. We demonstrate the feasibility of this procedure to determine the Pockels coefficient (r33) of a preferentially c-axis-oriented LiNbO3 film on a Si(100) substrate. Dispersion of effective r33 values at wavelengths between 0.3 and 0.8μm was obtained.