High radiation in GHz-THz range can be obtained both by free electron lasers (FELS) and solid state emitters. The pulsed optical excited emitters are not powerful and efficient yet. By means of the nonlinear frequency conversion the greater part of the GHz&THz radiation generation techniques were realized without phase matching. In these studies the crystals with hgih coefficient of nonlinear susceptibility were applied, their length being less than the length of coherence. Among nonorganic nonlinear crystals the semiconductor crystals GaAs. InTe, ZnTe, GaP, possess a high nonlinear coefficient d_14 of the order 100 pm/V or more, and among organic crystals DAST and DANPH have the same property. Since these semiconductor crystals are nonbirefringent, they cannot be phase matched by angle tuning.
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