Terahertz generation in quasi-phase-matching structures using femtosecond laser pulses

Abstract

Terahertz radiation generated by using femtosecond laser pulses was demonstrated in a periodically poled lithium niobate crystal. Two different terahertz radiations, forward and backward, could be obtained in the quasi-phase matching structures due to the difference frequency generation. A broadband femtosecond optical pulse contributes to such a difference frequency generation process, which occurs between an ultrashort laser pulse and a terahertz pulse. We achieved a backward terahertz radiation around 1.3 THz with quasi-phase-matching periods of 30.3, 30.5 and 30.8 pm by using about 150-fs laser pulses. The terahertz radiations with narrow-bandwidths could be easily controlled by varying the quasi-phase-matching structures.