Quality evaluation of quasi-phase-matched devices by far-field diffraction pattern analysis

摘要

Periodically poled ferroelectric crystals form highly efficient quasi-phase matched optical frequency conversion devices. For optimal performance of such devices, accurate period and duty-cycle are required throughout the poled region. For the quality evaluation we demonstrate a simple and a powerful technique using far-field diffraction measurement. Periodically poled lithium niobates were fabricated and etched out to reveal a surface-relief grating. The far-field diffraction pattern was analyzed to obtain statistical information for the duty-cycle. We explored the equivalence between the linear diffraction experiment and the conventional second-harmonic generation method for poling quality evaluation, through the Fourier-transform of the spatial modulation of domains.