Stilbazolium Tosylate Crystal Research Articles

Generation of single-cycle terahertz pulse using Cherenkov phase matching with 4-dimethylamino-N′-methyl-4′-stilbazolium tosylate crystal

This is the first report of single-cycle terahertz (THz)-wave pulse generation with a wide band (over 6 THz) and a high dynamic range (over 70 dB) using an organic nonlinear optical crystal, 4-dimethylamino-N′-methyl-4′-stilbazolium tosylate (DAST), and the prism-coupled Cherenkov phase-matching method. The prism-coupled approach allowed the use of a DAST crystal as a Cherenkov-type emitter for reduced light absorption by the crystal, resulting in the generation of single- and half-cycle THz pulse shapes, which were detected using dipole and bow-tie antennas, respectively. The resulting THz pulse generation is suitable for various THz-wave application technologies, such as tomography.

Influence of organic dopants on the optical properties of 4-N,N′-dimethylamino-N′-methyl stilbazolium tosylate crystals

Organic crystals of 4-N,N′-dimethylamino-N′-methyl stilbazolium tosylate (DAST), 2-amino-5-nitro pyridinium (2A5NP) and 2-amino-5-nitro pyridine toluene sulfonate (2A5NPTS) doped DAST crystals were grown by slow cooling method. The powder samples were examined by X-ray diffraction to estimate the lattice parameter values of the crystals. Fourier Transform Infra-Red (FT-IR) and Fourier Transform-Raman (FT-Raman) spectroscopic studies were performed to identify the various functional groups associated with the crystals. The four strong vibrational modes were observed at 1161cm−1, 1181cm−1, 1346cm−1 and 1577cm−1 contributing to linear electro-optic effect in DAST crystals. The Density Functional Theory (DFT) was used for FT-IR and FT-Raman analysis by means of the hybrid functional DFT/B3LYP with 6-311 G (d, p) basis set. The optical band-gaps were calculated from the UV–vis and photoluminescence spectra of pure and doped DAST samples.

Growth and characterization of novel organic 3-Hydroxy Benzaldehyde-N-methyl 4 Stilbazolium Tosylate crystals for NLO applications

The 3-Hydroxy Benzaldehyde-N-methyl 4-Stilbazolium Tosylate (3- HBST) is a new organic NLO crystal and it is a new derivative in stilbazolium tosylate family. In this work we have synthesized 3-HBST and the single crystal was grown by conventional slow cooling method. The structure and lattice parameters of the grown crystal were determined by the single crystal X-ray diffraction (XRD) technique and it is exhibiting good crystalline nature which is observed from the powder XRD. In order to check the crystalline quality the rocking curve was recorded using multi crystal X-ray diffractometer. The functional groups were identified from both FTIR and NMR spectral analyses. The π–π* and n–π* optical transition energy levels were estimated from the absorption peaks. The NLO property was confirmed by measuring relative SHG efficiency by Kurtz powder test; it shows 24 times higher SHG efficiency than that of urea. In order to test the mechanical stability the Vickers and Knoop micro hardness measurement were carried out and found that the micro hardness number decreases with increasing load. The melting point was determined from Differential Scanning Colorimetry (DSC).

Real-time terahertz wave imaging by nonlinear optical frequency up-conversion in a 4-dimethylamino-N′-methyl-4′-stilbazolium tosylate crystal

Real-time terahertz (THz) wave imaging has wide applications in areas such as security, industry, biology, medicine, pharmacy, and arts. In this letter, we report on real-time room-temperature THz imaging by nonlinear optical frequency up-conversion in organic 4-dimethylamino-N′-methyl-4′-stilbazolium tosylate crystal. The active projection-imaging system consisted of (1) THz wave generation, (2) THz-near-infrared hybrid optics, (3) THz wave up-conversion, and (4) an InGaAs camera working at 60 frames per second. The pumping laser system consisted of two optical parametric oscillators pumped by a nano-second frequency-doubled Nd:YAG laser. THz-wave images of handmade samples at 19.3 THz were taken, and videos of a sample moving and a ruler stuck with a black polyethylene film moving were supplied online to show real-time ability. Thanks to the high speed and high responsivity of this technology, real-time THz imaging with a higher signal-to-noise ratio than a commercially available THz micro-bolometer camera was proven to be feasible. By changing the phase-matching condition, i.e., by changing the wavelength of the pumping laser, we suggest THz imaging with a narrow THz frequency band of interest in a wide range from approximately 2 to 30 THz is possible.

Bridging a few terahertz to tens of terahertz: Inspection on a cost-effective, room-temperature operated measurement system based on frequency conversion via 4-dimethylamino-N′-methyl-4′-stilbazolium tosylate crystal

Based on experimental studies, we inspected the feasibility of a frequency conversion system, including both terahertz (THz) generation and detection, by using 4-dimethylamino-N′-methy-4′-stilbazolium tosylate crystal for wideband measurement. At 27 THz, more than five orders dynamic range in power have been obtained. Compared with typical pyroelectric detectors, it is four orders better in terms of sensitivity. Power calibration has been implemented and the minimum detectable pulse energy is 3 fJ, with a corresponding noise equivalent power of 22 pW/Hz1/2. For broadband operation, we have achieved good signal level downwards to 2.5 THz. Such a system can be an excellent complement to classical time-domain spectroscopy systems.

Pump-beam-induced optical damage depended on repetition frequency and pulse width in 4-dimethylamino-N ′-methyl-4′-stilbazolium tosylate crystal

We investigated the dependence of optical damage to an organic nonlinear optical crystal of 4-dimethylamino-N′-methyl-4′-stilbazolium tosylate (DAST) on the repetition frequency and pulse width of the pump beam used to cause the thermal damage. For a pump beam with a pulse width of 15 ns at a wavelength of 1064 nm, the highest damage threshold of 8.0 J/cm2 was measured for repetition frequencies in the range from 10 to 40 Hz. On the other hand, DAST crystals were easily damaged under the repetition rates from 50 to 100 Hz. For 600-ps pulses, a higher damage threshold that was a factor of 11 to 28 times higher in terms of peak intensity was obtained compared with that of 15-ns pulses. In both the cases of 15-ns pulse duration and 600-ps duration, we demonstrated that the thermal effects in DAST crystals dominated the optical damage, which depended on thermal accumulation and dissipation.