Improving the Efficiency of Cherenkov-Type Terahertz Generation in LiNbO3 by Using Longer Wavelength Optical Pump

Terahertz generation by optical rectification of femtosecond laser pulses in a structure comprising a 40-μm thick LiNbO 3 waveguide layer and an output Si prism has been investigated for different (800-2400 nm) central wavelengths of the optical pump. An increase in the optical-to-terahertz conversion efficiency for longer pump wavelengths has been obtained and attributed to higher saturation pump energy. In particular, record high conversion efficiency of 0.6 % has been achieved for μJ-level pump at 2100 nm.