Coherent tunable monochromatic Terahertz-wave generation using N-Benzyl-2-methyl-4-nitroaniline (BNA) crystal

Abstract

Widely tunable terahertz (THz) -wave generation using difference frequency generation (DFG) in an organic N-Benzyl-2-methyl-4-nitroaniline (BNA) crystal was demonstrated. An organic nonlinear optical (NLO) BNA crystal is one of the promising materials for efficient and strong THz-wave generation because of its potential to have a sufficiently large enough second-order optical nonlinearity. Large and high quality single crystals of BNA (φ8×30mm) were successfully grown by a vertical Bridgman method. The NLO coefficient d 33 of BNA crystal is about 230pm/V. It is the largest value reported for any yellow-colored NLO materials. BNA has low refractive index dispersion between the optical and THzwave region, therefore the colinear phase matching condition of the Type0 configuration is satisfied by using 0.7~1µm band pump wavelength. So, we developed a near-infrared dual-wavelength pump source for BNA-DFG. Two KTiOPO 4 (KTP) crystals were mounted on galvano scanners inside a double-pass optical parametric oscillator (OPO). It is pumped using a frequency-doubled Nd:YAG laser (532 nm, 8 ns, 100 Hz). The signal wave of the KTP-OPO output was controlled independently and rapidly using a galvano scanner. We successfully generated THz-wave using organic BNA crystal. The THz-wave generation range is from 0.1 to 15THz, while the pumping dual-wavelength is controlled in the 0.8-0.9µm range.

Optimization of Spatial Arrangement and Optical Nonlinearity of Chalcone Crystals by Halogen Substituted Donor Groups

“…A large nonlinear optical effect is generated so that the crystal exhibits a large nonlinear optical effect and an optical response speed. Among them, isophorone-based OH1 (2-(3-(4-hydroxystyryl)-5,5-dimethylcyclohex-2-enylidene)­malononitrile) crystals and aniline-based BNA ( N -benzyl-2-methyl-4- nitroaniline) crystals have good application prospects, both of which can be used as efficient terahertz wave radiation sources. − However, single-molecule crystals have high nonlinear performance, but also have the contradictions of low thermal stability and narrow light transmission range. It is necessary to optimize the design to obtain new nonlinear crystals with better performance.…”