Efficient generation of backward terahertz pulses from multiperiod periodically poled lithium niobate.

Backward terahertz pulses were converted from ultrafast pulses of a laser amplifier within multiperiod periodically poled LiNbO3 (PPLN) wafers. The average output powers of more than 2 microW were obtained from all six domain periods, corresponding to the frequency range of 217 GHz-2.373 THz. Among the six periods, the highest output power of 10.7 microW and the narrowest linewidth of 5.98 GHz were achieved at the periods of 66.5 microm and 150.0 microm, respectively.