Terahertz difference-frequency generation by tilted amplitude front excitation

To circumvent a velocity mismatch between optical pump and terahertz waves in electro-optic crystals, we propose to use dual-wavelength optical beams tilted with respect to their planes of equal amplitude. The tilt is achieved by transmission of a dual-wavelength laser beam through a diffraction grating placed on the crystal boundary. The proposed technique extends optical rectification of tilted-front femtosecond laser pulses to difference-frequency generation with longer (nanosecond) pulses. Our analysis of the technique for LiNbO(3) pumped at 1.3 μm and GaAs pumped at 1.55 μm shows its efficiency.