T. Thilak

Bio: T. Thilak is an academic researcher from B. S. Abdur Rahman University. The author has contributed to research in topics: Single crystal & Second-harmonic generation. The author has an hindex of 3, co-authored 4 publications receiving 95 citations.

Optical, thermal and mechanical studies on nonlinear optical material diglycine barium chloride monohydrate (dgbcm) single crystal

Abstract: The nonlinear optical single crystals of diglycine barium chloride monohydrate were grown by slow evaporation solution growth technique from the mixture of an aqueous solution of glycine and barium chloride in the ratio 2:1 at room temperature. The grown crystals were characterized by various techniques such as single crystals X-ray diffraction, FTIR, UV-Vis-NIR spectra, Vickers hardness studies, thermogravimetric analysis, and fluorescence spectra. Its second harmonic generation efficiency was measured by Kurtz and Perry powder technique using Nd:YAG laser.

Physical and optical study of potassium-doped meta-Nitroaniline crystal (mNAK)

Abstract: A nonlinear optical crystal of potassium-doped meta-Nitroaniline (mNAK) was grown by slow evaporation method using methanol as solvent. The growth mechanism was understood by chemical etching studies. The presence of potassium in the crystal was identified by energy-dispersive X-ray diffraction. Lattice parameters for the title crystal were determined by single-crystal X-ray diffraction and powder X-ray diffraction techniques, and the functional groups in the crystal were revealed by Fourier transform infrared study. Optical properties of the crystal were evaluated by UV-Vis-NIR transmission and absorption spectra in the range of 200–1000 nm. Thermal stability of the crystal was studied by thermo gravimetric analysis and differential thermal analysis. Mechanical properties of the crystal were analyzed using Vicker's microhardness technique. Second harmonic generation efficiency of the crystal was examined using pulsed Nd:YAG laser. Finally, the third-order nonlinear optical properties of the crystal were measured using single-beam Z-scan technique.

Effect of Fe3+ on third-order optical nonlinearity of KDP single crystals

Abstract: A series of trace Fe3+-doped KH2PO4 single crystals were grown using the conventional temperature cooling method. The Fe3+ ion content in the as-grown crystals and the corresponding transmission spectrum were measured, respectively. With an increase of Fe3+ ion concentration, the transmittance of the crystal gradually decreases within the wavelength range of 200 nm to 370 nm. Under picosecond pulse laser irradiation, third-order nonlinear optical characteristics were systematically measured at λ = 532 nm. The existence of nonlinear absorption and nonlinear refraction was demonstrated. The results show that the nonlinear refractive index n2 is positive, indicating the presence of a self-focusing effect for the as-grown crystals. Specially, nonlinear absorption and refraction have a heavy dependence on the Fe3+ ion content and crystal directions (II and z). With increasing Fe3+ ion concentration, a significant variation has been observed with respect to the nonlinear absorption coefficient β, nonlinear refractive index n2 and third-order nonlinear susceptibility χ(3). A similar pattern for II < z has been presented for nonlinear absorption and refraction. The investigations suggest that nonlinear absorption and refraction caused by distortion of the electron cloud might be associated with the H2PO4− and (FeO4)2− groups.

Crystal growth and characterization of semi-organic 2-amino-5-nitropyridinium bromide (2A5NPBr) single crystals for third-order nonlinear optical (NLO) applications

Abstract: Semi-organic nonlinear optical (NLO) 2-amino-5-nitropyridinium bromide (2A5NPBr) single crystals have been grown by slow evaporation solution technique (SEST) with the growth period of 60 days. The single-crystal XRD analysis confirms the unit cell parameters of the grown crystal. The crystallinity of grown 2A5NPBr was analyzed by powder X-ray diffraction (PXRD) measurement. The presence of functional groups of 2A5NPBr crystal was confirmed by Fourier transform infrared (FTIR) spectrum analysis. The optical transmittance of the grown crystal was analyzed by UV–Vis–NIR analysis. It shows good transparency in the visible and NIR region and it is favorable for nonlinear optical (NLO) device applications. The chemical etching study was carried out and it reveals that the grown crystal has less dislocation density. The photoconductivity study reveals that the grown crystal possesses positive photoconductive nature. The thermal stability of the crystal has been investigated by thermogravimetric (TG) and differential thermal analysis (DTA). The dielectric constant and dielectric loss as a function of frequency were measured. The electronic polarizability (α) of 2A5NPBr molecule has been calculated theoretically by different ways such as Penn analysis, Clausius–Mossotti relation, Lorentz–Lorenz equation, optical bandgap, and coupled dipole method (CDM). The obtained values of electronic polarizability (α) are in good agreement with each other. Laser damage threshold (LDT) of 2A5NPBr crystal has been measured using Nd:YAG laser with the wavelength of 1064 nm. Third-order nonlinear optical property of the grown crystal was studied by Z-scan technique using He–Ne laser of wavelength 632.8 nm.