A hydrogen-bonded organic nonlinear optical crystal for high-efficiency terahertz generation and detection

ETH Zurich, Institute of Quantum Electronics, Nonlinear Optics Laboratory, 8093 Zurich,Switzerland.
Optics Express (Impact Factor: 3.49). 11/2008; 16(21):16496-508. DOI: 10.1364/OE.16.016496
Source: PubMed


Broadband THz pulses have been generated in 2-[3-(4- hydroxystyryl)-5,5-dimethylcyclohex-2-enylidene]malononitrile (OH1) by optical rectification of sub-picosecond laser pulses. We show that OH1 crystals allow velocity-matched generation and detection of THz frequencies in the whole range between 0.3 and 2.5 THz for a pump laser wavelength range from 1200 to 1460 nm. OH1 crystals show a higher figure of merit for THz generation and detection in the optimized range compared to the benchmark inorganic semiconductor crystals ZnTe and GaAs and the organic ionic salt crystal 4-N,N-dimethylamino-4'-N'-methyl stilbazolium tosylate (DAST). The material shows a low THz absorption coefficient alpha3 in the range between 0.3 and 2.5 THz, reaching values lower than 0.2mm(-1) between 0.7 and 1.0 THz. This is similar as in ZnTe and GaAs, but much lower than in DAST in the respective optimum frequency range. A peak THz electric field of 100 kV/cm and a photon conversion efficiency of 11 percent have been achieved at a pump pulse energy of 45 microJ.

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    • "THz. The main absorption resonances occur at 1.45 THz and 2.85 THz (consistent with previous reports [26]). Here again we could not find reports on higher frequencies resonances, but from our spectrum we anticipate resonances around {4.9, 6.3} THz. "
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    ABSTRACT: The brightness of a light source defines its applicability to nonlinear phenomena in science. Bright low frequency terahertz (< 5THz) radiation confined to a diffraction-limited spot size is a present hurdle due to the broad bandwidth and long wavelengths associated with single-cycle terahertz pulses as well as due to the lack of terahertz wavefront correctors. Here, using a present-technology system, we employ a new concept of terahertz wavefront manipulation and focusing optimization. We demonstrate a spatio-temporal confinement of terahertz energy at its physical limits to the least possible 3-dimensional light bullet volume of lambda cubic. This leads to a new regime of extremely bright terahertz radiation reaching 40 PW/m2 intensity. The presented work is focused on the sub-5 THz range using small aperture organic crystals DSTMS and OH1. The obtained peak field of up to 5 GV/m and 17 Tesla is order of magnitude higher than any reported single-cycle field oscillation in the entire THz range from a laser-based system and surpassing large scale accelerator systems. The presented results are foreseen to have a great impact on future nonlinear terahertz applications in different science disciplines.
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    ABSTRACT: We report efficient terahertz (THz), pulse generation in a newly-developed single organic crystal OH1 (2-(3-(4-hydroxystyryl)-5,5-dimethylcyclohex-2-enylidene)malononitrile). The THz output characteristics were compared with those generated in inorganic nonlinear crystals such as ZnTe and CdZnTe. We achieved quasi single-cycle terahertz pulses at 1 kHz with an amplitude of ~8 kV/cm (peak-to-peak) at the central frequency of 0.8 THz. We believe that such high-power THz pulses can be effectively used for investigation of various nonlinear phenomena in the THz regime.
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    ABSTRACT: We demonstrate that the hydrogen-bonded organic nonlinear optical crystals COANP, OH1, and DANPH allow a highly efficient generation of a gap-free terahertz spectrum. COANP at the Ti:sapphire laser wavelength of 776 nm and OH1 at a wavelength of 1460 nm show a higher conversion efficiency than the respective benchmark materials ZnTe and DAST. An unprecedented photon conversion efficiency of 11 percent has been achieved in OH1. First results in DANPH indicate that this material holds an equal potential as OH1.
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