Feng Guoying

Investigation of laser-induced damage by nanoabsorbers at the surface of fused silica

A model for describing laser-induced damage in optical materials by nanosecond laser pulses is investigated. The laser-damage critical fluence is obtained based on calculating the light absorption of nanoabsorbers by using Mie theory and solving the heat equation. Considering a power law distribution of nano-absorbers, we calculated the damage probability at the surface of fused silica including Pt particles. The theoretical results calculated with appropriate parameters are applied to fit the experimental data in order to identify the properties of nanodefects.A model for describing laser-induced damage in optical materials by nanosecond laser pulses is investigated. The laser-damage critical fluence is obtained based on calculating the light absorption of nanoabsorbers by using Mie theory and solving the heat equation. Considering a power law distribution of nano-absorbers, we calculated the damage probability at the surface of fused silica including Pt particles. The theoretical results calculated with appropriate parameters are applied to fit the experimental data in order to identify the properties of nanodefects.

Relative importance of static contribution to the thermal shifts of spectral lines in Nd3+-doped Y3Al5O12 laser crystals

By means of the observed pressure and temperature dependences of several spectral lines in yttrium aluminum garnet Y3Al5O12 (YAG) : Nd3+ laser crystals, the static contribution due to lattice thermal expansion and the vibrational contribution due to electron-phonon interaction to the thermal shifts of these spectral lines are studied. It is found that (i) the importance of static contribution of a spectral line depends on the pressure dependence of this line, (ii) the static contribution always leads the spectral lines to shift to the blue (i. e. higher energy) with increasing temperature, while the vibrational one leads the lines to shift to the red, and (iii) the relative importance of static contribution changes not only from crystal to crystal (as suggested in the previous papers for hard or soft crystals), but also from spectral line to spectral line in the same crystal. So, the general statement in previous studies that the static contribution to thermal shift is negligibly small in a hard crystal is inappropriate.

A Temperature Sensor Based on a Symmetrical Metal-Cladding Optical Waveguide

A compact temperature sensor based on a symmetrical metal-cladding optical waveguide using free-space coupling is proposed and demonstrated theoretically and experimentally. The symmetrical Au-cladding optical waveguide is based on a thin LiNbO3 slab sandwiched between two metal films, which serve as the coupling layer and reflecting panel, respectively. The sensitivity of this sensor of 9.08 × 10−2 deg/°C, 6.6 × 10−2 deg/°C and 4.8 × 10−2 deg/°C corresponding to 3238-order, 3237-order and 3236-order modes, respectively, are obtained. Higher resolution is predicted with a larger linear expansion coefficient material and a higher resolution θ/2θ goniometer.