In this study, Au colloidal nanoparticle is performed by laser ablation method. The linear and nonlinear absorption of the
laser dye Rhodamine B dissolved in DI water with and without the presence of Au nanoparticles were investigated. The
emission spectra of the samples were studied. Results show the red shift of the fluorescence emission in the case of dye
with the presence of Au nanoparticles. The measurement of nonlinear absorption in Au, Au/Rhodamine B and
Rhodamine B solutions were carried out using the standard Z-scan technique. Our measurements indicate positive signs
for the nonlinear optical absorption coefficients of the samples.
In this paper, we report on designing a new raster-scanned CO2 laser heater for homogeneous heating of the disk-shaped substrates. This new design aims at concentrating the laser energy near the substrate peripheral edge, which mostly tends to remain cooler than the inner parts during the heating process. A comprehensive heat diffusion model has been developed to predict the temperature and its homogeneity on the substrate depositioning face. This new kind of laser heater can favorably be used in preparation of nanostructured thin films where the shape and size of the embedded nanoparticles depend on the maintained temperature during the depositioning time interval. This heater can also be used for CO<sub>2</sub> laser conditioning of the prepared thin films to enhance their damage threshold for high power laser applications.
In this work, preparation of zinc nanostructured thin films using the pulsed laser deposition (PLD) technique has been
described. Optical absorption spectera of the thin films have been obtained by Spectrophotometry. Morphology and
mean size of nanoparticles in the prepared nanostructured thin films were obtained by Atomic Force Microscopy.
Nonlinear optical properties of the films have been investigated using the well-known Z-scan technique. Our
measurements indicate positive signs for both nonlinear optical absorption coefficients and refraction indices of the
nanostructured zinc thin films. The used method for measuring the optical limiting properties of the thin films and its
results are also represented.
A method is introduced for small signal gain measurement in a low-saturation regime using an amplified spontaneous emission (ASE) footprint of a gain media. By this method, the ratio of intensities, with and without a reflector, is measured beside the bandwidth of the ASE, hence two equations are formed. An iterative solution of these equations will simultaneously determine both the small signal gain and the loss.
We report on designing a new raster-scanned CO2 laser heater for homogenous heating of the disk-shaped substrates during pulsed laser depositioning of materials. This new design aims at concentrating the laser energy near the substrate peripheral edge, which mostly tends to remain cooler than the inner parts during the heating process. A comprehensive heat diffusion model has been developed to predict the temperature and its homogeneity on the substrate depositioning face. Conduction and radiation heat transfer in three dimensions with temperature dependant material properties and a moving heat source are taken into account in this transient model. The model is validated by a simple stationary Gaussian laser heat source whose results are in good agreement with our measured values. Using this model, optimum conditions for the growth of garnets are calculated. Short heat-up times, some within minutes, are corroborated by calculations and measurements. An experimental procedure is designed to test the possibility of optical damage occurring in the substrate during this short temperature heat-up time.
In this paper we model and design a composite Yb:YAG/YAG hexagonal disk laser. In this edge-pumped thin disk laser
configuration, the pump light incidents from disk edges and propagates through the disk along the zigzag path and
repeatedly passes the gain medium, thus improve the pump uniformity and absorption efficiency. At the first we
calculate the absorbed pump distribution by ray tracing method; secondly with using the fraction of the absorbed pump
density as the heat source, the temperature distribution is simulated by 3D-FEM. Finally the output power is calculated
by solving the quasi-three-level system rate equations. The absorption efficiency, the pump uniformity and temperature
distribution are three effective parameters on the laser system operation. These parameters are investigated and
optimized by this model.