Efficient Cherenkov emission of terahertz radiation from an ultrashort laser pulse propagating along a waveguiding structure with nonlinear core

A scheme for efficient Cherenkov emission of terahertz radiation using nonlinear optical rectification of femtosecond laser pulses propagating in a sandwich-like structure is proposed and investigated. The structure consists of a thin nonlinear core covered by prisms with low terahertz absorption. We developed a theory of terahertz generation in such structures and calculated spatial distributions of the generated terahertz field, its energy spectrum and conversion efficiency. The developed theory predicts the optical-to-terahertz conversion efficiency of up to several percent in a 1 cm long and 1 cm wide Si-LiNbO₃-Si sandwich structure with a 40 mum thick nonlinear layer pumped by 5 muJ Ti: sapphire laser with pulse duration of 100 fs.