Abstract

A commercial argon-ion-pumped single-mode dye laser was used to Injection-seed a stable optical cavity with a XeCI gain medium. Figure 1 is a schematic diagram of the apparatus. The excimer oscillator cavity consisted of a 30% reflecting, 200-cm radius, concave mirror and a 90% reflecting flat. Intracavity apertures (not shown) were placed adjacent to the cavity mirrors to limit operation to a single transverse mode. The injection beam was spatially filtered and matched to the transverse mode of the oscillator cavity. A polarizing beam splitter and quarterwave plate were used to separate the injected and output beams. Because of table vibration, it was not possible to maintain longitudinal-mode matching of the cavity to the injection beam. Instead a PIN photodiode was used to monitor the transmission by the cavity of the injected beam. As with any etalon, the cavity transmission is a maximum when a longitudinal mode matches the injected frequency. When the photodiode signal exceeded a set threshold, the XeCI laser was fired. In this way, the frequency of the injection laser was certain to be within 0.1 of the mode spacing (i.e., <10 MHz). The measured output energy and pulse duration were measured to be 0.5 mJ and 100-ns (FWHM), respectively. Consequently, a 1-mW injection beam was sufficient to control a 5-kW excimer oscillator.

© 1988 Optical Society of America