Anuj Krishna

Key aspects of L-threoninium picrate single crystal: an excellent organic nonlinear optical material with a high laser-induced damage threshold

Recent trends focuses on the usage of nonlinear optical materials owing to their increasing demand in frontier areas of optical communication and switching applications. In the present work single crystal of L-threoninium picrate, an excellent material for nonlinear optical applications was grown using conventional slow evaporation solution technique to meet the increasing demand of photonics industry. The lattice parameters of the grown crystal were analysed by using powder X-ray diffraction, and it was found that it crystallised in monoclinic system with space group P21. The strain in the lattice of the grown crystal was calculated using Hall–Williamson relation. Crystalline perfection of the grown crystal was assessed using high resolution X-ray diffraction technique and observed that quality of crystal was fairly good. Optical transmission analysis and band gap evaluation were performed using UV-Vis spectroscopy. Laser damage threshold value for the crystal was also measured and was found to be higher than most of reported organic single crystals. Optical homogeneity of the crystal and birefringence was evaluated using modified channel spectrum method. Thermal behaviour of the grown specimen was examined by using photopyroelectric technique. Further its various mechanical properties, such as hardness, stiffness, youngs modulus, were measured using nanoindentation technique.

Single crystal growth of ninhydrin by unidirectional Sankaranarayanan–Ramasamy (SR) method by using a glass ampoule for nonlinear optical applications

An organic nonlinear optical single crystal of ninhydrin was grown by Sankaranarayanan–Ramasamy (SR) method by using specially designed glass ampoule. The good quality seed crystal has been prepared by conventional solution growth technique using double distilled water as the solvent. The lattice dimension of the grown specimen was identified from the powder X-ray diffraction analysis and found that it crystallized in a monoclinic system with non-centrosymmetric space group P21. The presence of functional groups was examined by Fourier transform infrared (FTIR) analysis and it was found that there was no incorporation of foreign elements during crystallization. The surface defects were assessed by optical microscope and the dielectric constant and dielectric loss were carried out by LCR meter. Laser damaged threshold, relative second harmonic generation (SHG) and phase matching were measured by using a high intensity Nd:YAG laser as a source having the wavelength of 1064 nm. Its thermal stability has been assessed by TG–DTA and specific heat measurements with respect to different temperatures. The optical studies show that the crystal has transmittance ability of light in the entire visible region.

Nucleation kinetics, growth, mechanical, thermal and optical characterization of sulphamic acid single crystal

Sulphamic acid (HSO3NH2) is a potential material that exhibits excellent piezoelectric and non-linear optical properties. Nucleation and growth kinetics give valuable information about the crystal growth process, which can be employed in the growth of large size crystals. Thus we have studied its nucleation parameters such as solubility, metastable zone width, induction period, interfacial tension, critical free energy, volume free energy change, critical nucleus and found that good quality sulphamic acid crystal can be grown at low temperature. Growth of good quality crystal was done by adopting slow evaporation solution growth technique at room temperature and as a result, good quality single crystal was grown. The grown bulk single crystal of the title compound was subjected to various characterization analyses. Its unit cell dimensions were confirmed using powder X-ray diffraction. Further its crystalline perfection was assessed using high resolution X-ray diffraction and X-ray topography techniques and it was found that it is reasonably good. Its various functional groups were identified from the Fourier transform-Raman method. Nanoindentation was performed to identify the load dependence and independence of hardness (H) and Youngs modulus (E) using the Oliver–Pharr method and it was found that both H and E exhibit peak load dependence. Photopyroelectric study was performed to identify its thermal properties such as thermal diffusivity (α), thermal conductivity (k), thermal effusivity (e), and heat capacity (cp). These studies reveal that it has high thermal stability compared to other single crystals. The optical homogeneity of the grown crystal was assessed using a birefringence interferometer and it was found to be reasonably good.

Synthesis and single crystal growth of L-proline cadmium chloride monohydrate and its characterization for higher order harmonic generation applications

The semi-organic non linear optical single crystal of L-proline cadmium chloride monohydrate was successfully synthesized and the single crystal was grown by a slow evaporation solution growth technique, using double distilled water as the solvent. The lattice dimensions of the grown crystal were examined by powder X-ray diffraction and it was found to belong to the orthorhombic crystal system with a noncentrosymmetric space group. Its crystallinity was assessed by a high resolution X-ray diffraction method and its structural imperfections were recorded using X-ray topography. The presence of functional groups was identified from heteronuclear correlation methods. Its optical behavior was examined by birefringence and photoluminescence and its optical constants were determined from UV-Vis. analysis. Its thermal and third order nonlinear optical properties were characterised by photopyroelectric and Z-scan methods, respectively. The mechanical and ferroelectric behavior was also assessed on the grown single crystal of L-proline cadmium chloride monohydrate.

Enhancement of thermoelectric figure of merit in Bi2Se3 crystals through a necking process

The growth of good quality bulk single crystals of bismuth selenide by employing a high-temperature vertical Bridgman technique with a specially designed ampoule having a provision for a necking process is reported. Several growth experiments were performed and reproducible results were obtained. The crystal structure and lattice dimensions were confirmed by powder X-ray diffraction (PXRD), the bulk crystalline perfection was assessed using high-resolution X-ray diffractometry and the good bulk crystalline perfection with an indication of layered structure was confirmed. Transmission electron microscopy (TEM) was carried out for the grown single crystal and confirmed the layered structure. High-resolution TEM (HRTEM) was also used to further assess the crystalline perfection. The direct measurement of d spacing obtained from HRTEM imaging was found to be in good agreement with the data obtained from PXRD. The thermal behavior was examined by differential scanning calorimetry and a sharp melting was found at 983 K, which revealed the purity of the bismuth selenide. The Seebeck coefficient and electrical and thermal conductivities were measured, and a thermoelectric figure of merit was calculated in order to assess the suitability of the crystal for thermoelectric applications such as refrigeration and portable power generation. Nanoindentation analysis was also performed for the first time.

Effect of ampoule support on the growth of organic benzimidazole single crystals by vertical Bridgman technique for nonlinear optical applications

Benzimidazole single crystals were grown using a vertical Bridgman technique with modified ampoule design. The thermal fluctuations during the melt were effectively controlled by the glass ampoule support which was filled with alumina wool in order to maintain a proper temperature gradient throughout the growth process. The unit cell dimensions of the grown crystals were assessed using powder X-ray diffraction technique. Comparative analyses have been carried out for both the crystals which were grown using a conventional ampoule and using the ampoule with support, via high resolution X-ray diffraction and it was found that there was a significant enhancement in crystalline perfection for the crystal which was grown using the ampoule with support. Further, optical transmission and photoluminescence studies on the grown crystals were carried out using UV-vis and photoluminescence spectroscopy and it was observed that there was a noticeable variation in the optical transmission and luminescence results.

Synthesis and nucleation studies on L‐leucine hydrobromide: a promising nonlinear optical material

To achieve good quality bulk size crystal growth, an assessment of the nucleation kinetics of a semi-organic l-leucine hydrobromide (L-LHBr) crystal was carried out using double-distilled water as solvent medium. The effect on metastable zone width (MSZW) with increasing temperature and on induction period with varied supersaturation level was determined experimentally and was found to be very well in accordance with the nucleation theory prospects. Thereafter, various other nucleation parameters, such as Gibbs free energy and interfacial energy, were also determined. The knowledge of these nucleation parameters indicated the requisite temperature domain and the appropriate growth technique, leading to the successful single-crystal growth of L-LHBr by slow cooling in the temperature range 298-291 K. The cooling rate of 0.25 K per day was optimized after repeated trials. X-ray diffraction and Raman analysis were performed on grown crystals for the verification of the material. High-resolution X-ray diffraction analysis was used to assess the crystalline perfection of the grown crystals. To further explore the properties of the grown crystals, photoluminescence and time decay studies, etching analysis, and Z-scan measurements were performed.

Crystalline perfection, thermal, mechanical and optical investigations on solution grown l-arginine monohydrochloride single crystal

In the present work we report crystallization and detailed analyses on l-arginine monohydrochloride single crystal an efficient material for nonlinear optical applications. The crystal of titled material was grown using slow evaporation solution growth technique using double distilled water as solvent. Single crystal X-ray diffraction technique revealed that lattice dimensions of grown crystal are in good agreement with the reported literature and it crystallised in monoclinic crystal system. High resolution X-ray diffraction study revealed that crystalline perfection is fairly good. Optical homogeneity and variation of birefringence across the sample cross-section was studied using birefringence interferometer. Specific heat and thermal conductivity of grown crystal was measured using photopyroelectric technique and was found to be higher than many organic and inorganic crystals. Its various mechanical properties and resistance toward deformation was examined using nano-indentation technique. Further laser damage threshold value and phase matching angle was also measured.

Structural, optical, mechanical and dielectric studies of pure and doped L-Prolinium trichloroacetate single crystals.

In the present work, pure and metal substituted L-Prolinium trichloroacetate (LPTCA) single crystals were grown by slow evaporation method. The grown crystals were subjected to single crystal X-ray diffraction (XRD), powder X-ray diffraction, FTIR, UV-Visible-NIR, hardness, photoluminescence and dielectric studies. The dopant concentration in the crystals was measured by inductively coupled plasma (ICP) analysis. Single crystal X-ray diffraction studies of the pure and metal substituted LPTCA revealed that the grown crystals belong to the trigonal system. Ni(2+) and Co(2+) doping slightly altered the lattice parameters of LPTCA without affecting the basic structure of the crystal. FTIR spectral analysis confirms the presence of various functional groups in the grown crystals. The mechanical behavior of pure and doped crystals was analyzed by Vickerss microhardness test. The optical transmittance, dielectric and photoluminescence properties of the pure and doped crystals were analyzed.

An in-depth study into the growth aspects and characteristic properties of ethyl 4-amino benzoate: a potential candidate for electro-optical applications

In the present work we report the growth of a bulk size ethyl 4-amino benzoate crystal, a potential candidate for electro-optical applications, using an indigenously developed single zone transparent resistive furnace because of observed difficulties involved in its growth via a solution growth technique. The structure of the grown crystal was examined using single crystal X-ray diffraction and it was found that it crystallized in an orthorhombic crystal system with the non-centrosymmetric space group P212121. The lattice parameters of the title material were further analysed using powder X-ray diffraction and they were found to be in agreement with the single crystal X-ray diffraction results. The strain in the lattice of the grown crystal was evaluated using the Hall–Williamson relation. The quality of the grown crystal was examined using a high resolution X-ray diffraction technique. Surface defects on the grown crystal were analysed using an etching technique. The transparency of the grown crystal was assessed using UV-vis spectroscopy and it was observed that the crystal possesses reasonably good transmittance over the visible spectrum. The optical band gap was also evaluated using Taucs plot. Furthermore, the laser damage threshold value was calculated using a Nd:YAG laser. Moreover, the thermal parameters and mechanical properties of the grown crystal were evaluated using photopyroelectric and nano-indentation techniques and it was observed that the crystal possesses quite fair thermal stability, however, the mechanical strength was low. With reduction in defects as observed it could be a potential candidate for non-linear optical applications.