Si–LiNbO3–air–metal structure for concentrated terahertz emission from ultrashort laser pulses

Abstract

A planar Si–LiNbO3–air–metal structure is proposed as a further development of the highly efficient optical-to-terahertz conversion scheme in sandwich structures that was recently demonstrated. The new structure allows one to collect the terahertz emission into one spatial direction and to control its spectrum by varying an air gap between the metal substrate and the LiNbO3 layer. While the overall increase in the terahertz generation can reach a factor of 2, the spectral density in the interesting for practical application interval 0.5–1.5 THz can be increased by a factor of 3.5–4.