Domain Wall Characterization in Sub-μm Period Ferroelectric Crystals by Čerenkov Second Harmonic Generation
Molecular Physics seminar
Monday 27 April 2015
to 11:00 at
Chang Liu (Molecular Physics Division)
As a method of improving the conversion efficiency in nonlinear optical processes, quasi-phase-matching (QPM) is becoming more and more popular during the last several decades. Usually, QPM is achieved by electric field periodic poling in ferroelectric crystals. Thus, there is a need to investigate the poling quality nondestructively and sensitively. In this thesis, I proposed a new method to utilize Čerenkov Second Harmonic Generation (CSHG) for domain structure characterization, which is noninvasive and can probe deep in the crystal bulk. Based on Boyd and Kleinman’s theory, I derived the coupled wave equations and the solution for CSHG with Gaussian laser beams in periodically poled crystals, according to which the CSHG power is proportional to the domain wall density (twice the reciprocal of the QPM grating period). Additionally, I explained the characteristic angle of nonlinear Cerenkov radiation with Fermat’s principle.