Narrow Results

The laser damage resistance of fused silica optics depends significantly on the surface quality. In this work, anisotropic etching with inert ion beams at various ion incident angles was performed to investigate the evolution of the fused silica surface. The results show that the surface is smoothed when the incident angle is below $30^{\circ }$. However, the fused silica surface starts to become coarse owing to the formation of nanostructures on the surface when the incident angle exceeds $30^{\circ }$. Further, ion beam etching at a large incident angle of $70^{\circ }$ removes subsurface defects and less induces nanostructures, resulting in reduction of the surface roughness. The concentrations of impurities and defects are both significantly reduced after ion beam etching. The surface quality, subsurface and surface defects, and surface impurities determine the variation in the laser damage threshold of fused silica with the ion incident angle. The results demonstrate successful application of ion beam etching to improve the laser damage resistant characteristics of fused silica optics. Ion beam etching is a very versatile tool that provides physical erosion to anisotropically mitigate surface damage of fused silica.

Organic single crystals of Benzilic Acid (BA) were grown by slow solvent evaporating method by using acetone as solvent. The unit cell parameter values and the crystal system are recognized by using single crystal XRD technique. The optical assessment of BA molecules is observed by with UV-Vis spectral analysis as the ultraviolet range between 200 and 400 nm and the visible region between 400 and 800 nm. The nonlinear optical (NLO) properties such as second harmonic efficiency nature of BA crystal were analyzed using Nd:YAG laser. The laser-induced damage threshold assessment of BA crystal is measured as 2.76 GW/cm². From the Density Functional Theory (DFT), the molecular structural feature and vibrational frequencies were defined by using the Gaussian system along with comparisons of experimental frequencies. Using the DFT method, the derived vibrational frequency values showed an admirable accord with experimental frequencies. The charge interactions within the BA molecules are confirmed by HOMO and LUMO energy value. The first-order molecular hyperpolarizabilities, dipole moment, polarizability and Mulliken charge analysis of the BA molecule are also evaluated.

A semi-organic nonlinear optical material L-Arginine tetrafluoroborate (LAFB) was synthesized as single crystal using Slow Evaporation Technique. Various properties of this material were analyzed to make it suitable for NLO applications. The structural behavior of the material was determined by single crystal XRD and found that the crystal has orthorhombic structure and was synthesized with P2₁2₁2₁ space group. The High-Resolution X-Ray Diffraction (HRXRD) study was conducted to determine the change in the lattice parameters resulting from strain, defects or by other means in LAFB material. The diffraction curve analysis show that the grown crystal consisted of interstitial type point defect. The Shock Damage Threshold (SDT) measures the stability of the compound against shock, the analysis exhibits that under Mach number 2.2 up to 10th shock no significant cracks were observed in the crystal but damage area of the crystal was increased. The mechanical behavior of the sample against highly intense laser was analyzed through Laser Damage Threshold (LDT). The calculated value of LDT was to be 0.75GW/cm² for 1 pulse per second whereas it decreased to 0.57GW/cm² for 10 pulse per second. To explore the mechanical properties of the material, Nano indentation was carried out, by which the values of H${}_0=131.548$MPa and E${}_0=4.38769$GPa were obtained.

Hydrophobic antireflective coating is fabricated by physical vapor deposition. The optical, contact angle and laser damage resistance properties are investigated, respectively. The transmittance of the antireflective coating with hydrophobic layer is 99.58% at 1064 nm with normal incidence. The contact angle with water is 115.6${}^{\circ }$. The laser damage threshold of the zero probability is 22 J/cm² at 1064 nm with the 12 ns pulse width. This new hydrophobic antireflective coating can be applied in the areas of astronomical optics, laser medical equipment and solar energy, etc.

Single crystals of L-valine zinc hydrochloride (LVZHCl), a novel semi-organic nonlinear optical material were synthesized and grown from aqueous solution by slow evaporation method at room temperature. The cell parameters of LVZHCl had been determined using single crystal X-ray diffraction technique. The linear and non-linear optical properties of the crystals were studied by Fourier Transform Infrared, Ultraviolet Visible Near infrared, ac impedance, laser damage threshold, and second harmonic generation analysis. The thermal stability of the crystals was assessed by Differential thermal-Thermogravimetric analysis. The crystallinity and mechanical properties of the crystals were studied by Dielectric behavior and Vickers microhardness test.

In the present study, L-alanine crystal is grown with cobalt chloride as dopant by low temperature solution growth using slow evaporation technique at room temperature. The lattice parameters of the grown pure and cobalt chloride doped L-alanine crystals were determined by the single crystal X-ray diffraction technique. The presence of the elemental composition such as cobalt chloride present in the L-alanine lattice was confirmed by energy dispersive X-ray analysis. The optical transmittance, absorbance, reflectance was measured and used to study the optical properties of the pure and doped L-alanine crystal. The pure L-alanine crystal has high optical transmittance in the whole visible range and UV transparency with lower cutoff wavelength at 240nm. By adding cobalt chloride to L-alanine crystal, the transmittance decreases the value of cutoff shifts to the higher wavelengths. Nonlinear optical studies reveal that the SHG efficiency and laser damage threshold energy increases when the L-alanine crystal is doped with cobalt chloride. From microhardness studies, it is observed that the cobalt chloride doped L-alanine crystal is harder than the pure crystal.

An organic nonlinear optical centric single crystal, sulphanilic acid monohydrate (SAM) was successfully grown by slow evaporation method. The cell parameters of the grown crystal were assessed by single crystal XRD. The UV absorption edge was found to be 249nm providing a wide optical transmittance covering the visible region. The thermal, mechanical and dielectric properties of the grown crystal were examined. Fluorescence emission spectrum was recorded and lifetime was studied. A multiple shot laser technique was adopted to investigate the surface laser damage of the crystal. The third-order nonlinear optical characteristics of the grown crystal, investigated by $Z$-scan technique attest its suitability in the field of nonlinear optical applications.

Since the discovery of lasers, high-quality nonlinear optical (NLO) single crystals have served as the foundation for the creation of novel, cutting-edge devices that meet societal demands. Modern optoelectronic applications such as telecommunication lasers, optical fibers, photodiodes, solar cells, etc. favor high-performance nonlinear optical single crystals with improved optical nonlinearity. Organic crystals are extensively explored for these applications because of their high NLO coefficient. This paper deals with the problems and advancements of organic nonlinear optical single crystals. Here, we review the growth and characterizations of various tosylate family crystals from the vast realm of organic single crystals and their potential applications in the field of optoelectronic devices. Various properties like linear and nonlinear optical, thermal, mechanical, and laser damage threshold values for these samples have been summarized. The attempts are made for highlighting how these tosylate (p-Toluenesulfonic acid based) family crystals can be realized into efficient optoelectronic devices by summarizing variously reported cut-off wavelengths and their wide transmission ranges.