Efficient multi-cycle terahertz generation based on a multi-lines source

We demonstrate efficient multicycle THz generation with periodically poled lithium niobate crystals via difference frequency generation using a multiple-line source. The THz yield for different crystal lengths as well as pump pulse durations is investigated. Our experimental results show excellent agreement with the theoretical predictions. By employing a 20-mm PPLN crystal, up to 2.7 μJ at 0.5 THz was obtained with 6.2 mJ input pump pulse energy (130 mJ/cm² peak fluence) at 77 K, corresponding to an internal conversion efficiency of 0.3%. The record internal efficiency at the peak fluence of 130 mJ/cm² shows the great potential for high-energy multicycle THz generation with a multiple-line source.