Characteristics of efficient few-cycle terahertz radiation generated in as-grown nonlinear organic single crystals

•Efficient terahertz (THz) wave generation in highly nonlinear organic crystals.•Direct application of as-grown organic crystals without additional treatments.•Generation of high-field THz wave (>110 kV/cm) in a compact configuration.•High optical-to-THz conversion efficiency (3.1 × 10−4).

We investigated efficient terahertz wave generation by optical rectification in as-grown nonlinear organic single crystal HMQ-T (2-(4-hydroxy-3-methoxystyryl)-1-methylquinolinium 4-methylbenzenesulfonate). Optimal thickness of crystals directly available by a slow cooling method in methanol solution enabled us to achieve high-field few-cycle THz waves at 800-nm pumping. With 95-mW pumping at 1-kHz repetition rate, an optical-to-THz conversion efficiency of 2.7 × 10−4 was achieved and the THz electric field strength, measured by electro-optic sampling, was as high as 110.1 kV/cm. Such an efficient THz source based on as-grown HMQ-T crystals can be used for investigation of various nonlinear phenomena in the THz spectral region.