Iraj K. Pour

Sudden onset of strong absorption followed by forced recovery in KrF laser-irradiated fused silica

A high-purity synthetic fused silica sample (Suprasil 2) was irradiated by a KrF laser at 248 nm, 300 Hz, and 500 mJ/cm(2). Transmission at 248 nm, transmission at 210 nm, and fluorescence at 650 nm were monitored in real time. The sample starts out in a weakly absorbing state. Then, after several million pulses, it experiences a sudden increase in 248-nm absorption with accompanying dramatic changes in its relaxation and fluorescence behavior. Further irradiation leads to (partial) bleaching of the UV absorption.

Effects of KrF laser radiation on fused-silica glass: a comparison of samples exposed in air vs vacuum

High-purity synthetic fused silica glass is known to undergo changes in optical properties during high repetition rate KrF laser exposures. (Results of studies on six glass types irradiated in air are summarized elsewhere at this symposium.) We have also irradiated several samples in vacuum (248 nm, 300 Hz, (Phi) equals 400 mJ/cm2). Transmission at 248 nm, transmission at 210 nm, fluorescence at 650 nm, and vacuum cell pressure were monitored in real time. Although bulk outgassing is expected to be very slow at room temperature, our results indicate that the vacuum environment does affect the interior of the sample. Furthermore, a curious irradiation effect on the transmission of the CaF2 windows used on the vacuum cell is discussed.

New laser texturing process of magnetic disks for stiction reduction

Microscopic bumps of heights being tens of nm can be produced on a smooth nickel-phosphorus disk substrate using Q-switched laser pulses from a diode-pumped laser. This technique is being used in the manufacture of high-end disk drives where tens of thousands of such bumps are produced to form a dedicated landing-zone racetrack for the magnetic head to land and takeoff without stiction.