Optical Terahertz Sources Based on Difference Frequency Generation in Nonlinear Crystals

Terahertz (THz) sources, ranging from 0.1 THz to 10 THz, between microwaves and infrared waves, have important applications in spectral detection, medical imaging, communication, etc. Difference frequency generation (DFG) is an effective method for generating terahertz with the characteristics of low cost, simple structure, widely tunable range, no threshold, room-temperature operation. This paper reviews various optical sources difference based on nonlinear crystals, including DFG inorganic organic quasi-phase-matching (QPM) waveguides, cavity-enhanced DFG, cascaded DFG. Their recent advances, as well their advantages disadvantages, are fully present discussed. review expected provide a comprehensive reference researchers this field quick understanding crystals.