Investigation On Chopping Descend Edge Of KrF Laser Pulse Using Optical Breakdown

KrF laser has characteristics of short-pulse, high-efficiency, high-power and broad-frequency. It is applied to many fields in scientific research and industry, especially provided with promising potential in Inertia Confinement Fusion (ICF) study. And that short-pulse are required in ICF system, so we have to compress pulse width. Optical breakdown is an effective method used in laser pulse control. Accordingly, it is important to study the method of optical breakdown using in KrF laser pulse clipping.In this dissertation, the KrF laser pulse clipping by optical breakdown is investigated theoretically and experimentally, the parameters have effect on the laser pulse width and shape is analyzed.In theory, based on the plasma density evolutive velocity equation, the expression of optical breakdown threshold is obtained, the theoretical model of optical breakdown is constructed. By numerically simulating, the breakdown threshold versus parameters of wavelength, laser width, pressure and initialized electron density are obtained.In experiment, the optical breakdown of SF₆ by a KrF laser were investigated. We obtained the functions of pulse width and shape versus pressure, laser energy and breakdown points, and compared the experimental results with the theoretical calculation. With the pressure of SF₆ increasing, the pulse width first decreases then increases, and finally reaches a saturated value. The pulse width decreases with the energy increasing. The laser energy has effect on the pulse shape and its stabilization. With the delay time increasing, the pulse width increases and the descend edge of pulse decreases.