Highly efficient optical-to-terahertz conversion in a sandwich structure with LiNbO3 core

We demonstrate experimentally the efficiency of a recently proposed scheme of terahertz generation based on Cherenkov emission from ultrashort laser pulses in a sandwich structure. The structure has a thin nonlinear core covered with a prism of low terahertz absorption. Using an 8 mm long Si-LiNbO3- BK7 structure with a 50 mu m thick LiNbO3 core, we converted 40 mu J, 50 fs Ti:sapphire laser pulses into terahertz pulses of similar to 3 THz bandwidth with a record efficiency of over 0.1%. (C) 2009 Optical Society of America