THz Pulse Generation Emitted from Slant-Stripe-Type PPLN Via Optical Rectification Effect

To generate THz wave efficiency, phase-matching condition and small absorption of THz waves in nonlinear crystal are required. PPLN has attracted attention as a promising candidate for nonlinear crystal for THz wave generation, since periodically poled lithium niobate (PPLN) can be controlled its phase matching condition by designing periodically-poled structure. In case of ultrashort pulse pumping, multi-cycle THz pulses are obtained from PPLNs via optical rectification effect [1]. In this case, THz pulses with an arbitrary frequency shift are expected to be obtained by optimizing the periodic structures of the PPLNs [1,2]. Utilizing this feature, it is expected that multi-cycled THz pulses can be applied to radar techniques with high resolution. However, the pulse length is limited by 10∼30 ps owing to absorption of PPLN. Note that PPLNs have absorption coefficient of approximately a few tens cm−1 at room temperature [3].