Optical poling and frequency doubling effect is one of the effective manners to induce second order nonlinearity and realize frequency doubling in glass materials. The classical model believes that an internal electric field is built in glass when it’s exposed by fundamental and frequency-doubled light at the same time, and second order nonlinearity appears as a result of the electric field and the orientation of poles. The process of frequency doubling in glass is quasi phase matched. In this letter, the physical process of poling and doubling process in optical poling and frequency doubling effect is deeply discussed in detail. The magnitude and direction of internal electric field, second order nonlinear coefficient and its components, strength and direction of frequency doubled output signal, quasi phase matched coupled wave equations are given in analytic expression. Model of optical poling and frequency doubling effect which can be quantitatively analyzed are constructed in theory, which set a foundation for intensive study of optical poling and frequency doubling effect.
We measured the Raman spectra of the ν1 mode in KDP crystal over the temperature range from 285.3 K to 345.2 K. And the temperature dependence of the Raman characteristics (Raman shift, FWHM and intensity) were well analyzed. The result reveals that with temperature increasing the ν1 mode displays a red-shift and the linewidth broadens, but the scattering intensity shows no obvious tendency. The stimulated Raman scattering (SRS) gain coefficient of the ν1 mode decrease about 12% at 345.2 K.