Enhanced third harmonic generation by introducing quasi-phase mismatches due to electro-optic effect

Abstract

Third harmonic can be realized by the coupled second-harmonic (ω1 + ω1 → ω2) and sum-frequency (ω1 + ω2 → ω3) generation. However, in quasi-phase matching conditions, the efficiency of third harmonic is usually low due to the larger coupling coefficient ratio. In this paper, the third-harmonic generation in a periodically poled LiTaO3 has been experimentally studied, where the electro-optic effect was employed to manipulate the phase mismatches and energy distribution of the coupled waves. With the DC electric field varying from 0 to 140 V/mm, the output of third harmonic can be enhanced from about 95 to 312 mW. The method provides a simple and convenient way to control the efficiencies of frequency conversion.