Arbitrary wave-form-pulsed power source for flash-lamp-pumped solid-state lasers

An arbitrary wave-form-pulsed power source for driving pulsed flash lamps electrically to pump quasi-continuous-wave Nd:YAG lasers has been developed. It is based on a high-frequency switching converter as opposed to conventional pulse-forming network or linear power amplifier circuit-based pulse generators. The system can generate rectangular pulses through the flash lamp with fine adjustment in pulse parameters over a wide range. The system can also generate an arbitrary-shaped pulsed current within a bandwidth of 500 Hz. The design of the system and the results in the form of rectangular- and arbitrary-shaped pulsed-current wave forms with different pulse parameters are presented. In addition, a burst of consecutive pulses with different arbitrary shapes can also be generated as desired or as programed. The developed pulsed power source offers advantages of more flexibility in control and adjustment of output pulse parameters, arbitrary-shaped pulse generation, better efficiency, compactness, and higher reliability as compared to the pulsed power sources based on normal schemes. The electronic system developed is of immense value in studying the dependence of flash-lamp impedance, spectral output, and energy-transfer efficiency on pulse parameters as well as optimization of these parameters for use in various laser material processing applications

MORPHOLOGY OF SELF-SUPPORTING POROUS SILICON LAYERS

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Chemical treatment of photoluminescent porous silicon

Porous silicon layers formed by electrochemical anodizing show photoluminescence in the visible region. We report on the effect of chemical treatments such as hydrofluoric acid dip, ammonium fluoride solution treatment and boiling water treatment on the photoluminescence of porous silicon. In view of our results the mechanism of photoluminescence of porous silicon is discussed

Generation of Crystal-Structure Transverse Patterns via a Self-Frequency-Doubling Laser

Two-dimensional (2D) visible crystal-structure patterns analogous to the quantum harmonic oscillator (QHO) have been experimentally observed in the near- and far-fields of a self-frequency-doubling (SFD) microchip laser. Different with the fundamental modes, the localization of the SFD light is changed with the propagation. Calculation based on Hermite-Gaussian (HG) functions and second harmonic generation theory reproduces well the patterns both in the near- and far-field which correspond to the intensity distribution in coordinate and momentum spaces, respectively. Considering the analogy of wave functions of the transverse HG mode and 2D harmonic oscillator, we propose that the simple monolithic SFD lasers can be used for developing of new materials and devices and testing 2D quantum mechanical theories