Sungok Kwon

Development and Characterization of a 400-W Slab-type Nd:YAG Gain Module

We have developed a slab-type Nd:YAG gain module based on the techniques of conduction cooling and end pumping. The Nd:YAG slab is end-capped on both ends by undoped pure YAG and is pumped through the end-caps by stacked arrays of laser diode bars. The slabs surfaces of total internal reflection are in contact on both sides with microchannel cooling blocks which are cooled by water circulation. The power oscillator based on the gain module generates more than 400 W at 1-kW pumping with a slope efficiency of 55%. The small-signal gain of the gain module is 10 in a single zig-zag pass, and the amplified beam shows a near diffraction-limited beam quality.

BHP jet stabilization of COIL

A COIL (Chemical Oxygen-Iodine Laser) of 2.2 kW output power has been developed in Korea. The effects of stability and uniformity of the BHP(Basic Hydrogen Peroxide) jet columns on the operation of the COIL are reported. In this paper, the uniform jet speed distribution ofjet SOG (JSOG) in a supersonic COIL is achieved by using the centrifugal pump. And the vane plate in front of BHP jet plate is installed to suppress the turbulent BHP flow generated by the centrifugal pump. The stability and uniformity of BHP jet columns are increased by installing the vane plates. Substantially, the chemical efficiency is increased up to 21 .7 %.

Performance optimization of COIL using the visualization of supersonic flow

This paper describes the results achieved in the development of a chemical oxygen iodine laser (COIL) for industrial applications. The COIL was designed to obtain kW class output power with jet type singlet oxygen generator (SOG). The output power with subsonic flow was 230 W at 15 mmole/sec chlorine flow rate. The real-time holographic interferometer with a digital high-speed camera was applied to the visualization of mixed gas flow in COIL. The visualization of gas flow shows the profile of the variation of refractive index and can be applied to the measurement of the variations in the pressure and the temperature of the gas.

Fast neutron emission from a deuterated polystyrene solid target irradiated by a high-intensity laser pulse

Fast neutrons were generated from a deuterated polystyrene (C8D8) solid-target irradiated by a high-intensity laser. A TOF neutron signal is analyzed in detail. A neutron yield of 1206 n/pulse is estimated from a CR-39 neutron detection, and a maximum deuterium ion energy of 76 keV is measured from a Faraday cup signal. The employed laser has a 27-fs pulse width and a 260-mJ pulse energy.

Holographic visualization of the mixed gas in COIL

The chemical oxygen iodine laser (COIL) is an efficient source of high power with excellent beam quality and flexibility in beam delivery through an optical fiber. The understanding of density distribution of the gas flow in a COIL is important because the uniform gas flow is required for uniform laser output. The knowledge in the density distribution show the profile of the pressure and the temperature. Many optical methods such as shadowgraphy, schlieren, Mach-Zehnder interferometer have been applied to visualize the density distribution of mixed gas in various fields, but the visualization of gas flow in a COIL has never been investigated. The measurement of density distribution by the interferometric visualization has the advantage of quantitative analysis and high sensitivity. In the paper, the gas flow in a COIL was visualized with a real-time holographic interferometer and recorded with a high-speed camera under an environment with some vibration. The interference fringe patterns induced by the variations in the refractive index of gas were measured both in the iodine mixing region and in the laser gain region.