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A laser-induced breakdown spectrometer (LIBS) was built and optimized to detect levels of toxic elements such as lead, cadmium, and arsenic present in the roots of extracted teeth of smokers and nonsmokers. Sixty extracted teeth from patients having a history of chronic periodontitis were divided into two groups of 30 teeth each for smoker and nonsmoker patients and, as controls, a third group of 30 patients who did not have a history of chronic periodontitis. The respective elemental concentration (Pb, Cd, and As) 23-29, 0.26-0. 31, and 0.64-11 ppm are for nonsmokers, 35-55, 0.33-0.51, and 0.91-1.5 ppm are for smokers, and lastly 0.17-0.31, 0.01-0.05, and 0.05-0.09 ppm are for control group. In order to test the validity of the results achieved using our LIBS system, a standard inductively coupled plasma (ICP) technique was also applied for the analysis of the same teeth samples, and ICP results were found to be in excellent agreement with our LIBS results. In addition to this, the gingival index, plaque index, clinical attachment loss (CAL) and probing pocket depth were also recorded. Our LIBS spectroscopic analysis showed high levels of lead, cadmium, and arsenic concentration on root surfaces of teeth, which may be due to CAL.

Second harmonic generation (SHG) from metasurfaces consisting of square array of split ring, heptagon and triangle cross-polarized double resonant resonators, is investigated both experimentally and numerically. The structures are fabricated on single crystalline Au plates using Focused Ion Beam technique. Array of the triangular structure exhibits most efficient SHG. Experimental observation is explained reasonably well by theoretical evaluation of SHG using the overlapping integral of nonlinear polarization and the microscopic field distribution on the metal surface at the SHG frequency taking phase relation between the two fields into account.

A spectrometer based on pulsed UV laser-induced breakdown spectroscopy (LIBS) and a highly sensitive intensified charged coupled device camera was developed to determine the carcinogenic substances like fluorine in various brands of cigarettes available commercially. In order to achieve the high sensitivity required for the determination of trace amounts of fluoride in cigarettes and eventually the best limit of detection, the experimental parameters (influence of incident laser energy on LIBS signal intensity and time response of plasma emission) were optimized. In addition, the plasma parameters like electron temperature and electron density were evaluated using Boltzman's plot for cigarette tobacco for the first time. To the best of our knowledge, LIBS has never been applied to determine the fluorine concentration in cigarettes. Along with the detection of fluorine, other trace metals like Ba, Ca, Ni, Cu, and Na were also detected in cigarettes. For determination of the concentration of fluorine, calibration curve was drawn by preparing standard samples in various fluoride concentrations in tobacco matrix. The concentration of fluorine in different cigarette tobacco samples was 234, 317, 341, and 360 ppm respectively, which is considered to be much higher than the safe permissible limits. The limit of detection of our LIBS spectrometer was 14 ppm for fluorine.

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Metasurface consisting of square array of obtuse isosceles triangle metaatoms is found to exhibit much more efficient second harmonic generation (SHG) compared to that of split ring resonators and its heptagonal modification, experimentally as well as numerically. All of them are designed to lack inversion symmetry in horizontal direction but to have vertical symmetry, and to meet the double resonance condition for vertically-polarized fundamental and horizontally-polarized SHG waves. SHG efficiencies were estimated numerically for each structure by evaluating an overlap integral of second order nonlinear polarization and field distribution at the SHG wavelength. The large overlap integral for the triangle metasurface is ascribed to the nonlocal response at the SHG wavelength. Current induced at the center of the triangle near the obtuse angle by horizontally polarized light at SHG wavelength flows toward two corners of acute angles. As a result, polarization charges oscillate in time at the surfaces of two acute corners, which results in strong field oscillation away from the center where the electric field is applied to majority of free electrons. Experimentally observed wavelength dependence of SHG efficiencies for the three metasurfaces are reasonably reproduced by a numerical estimation.