Abstract

The incorporation of discrete ceramic capacitors into a Blumlein-type circuit in a N₂ laser was first introduced by Nagata and Kimura.¹ This design has the advantage of allowing for a large energy storage capacity in a fast current discharge circuit. We have developed an improved version of such a nitrogen laser system. Figure 1 shows a double-decker type laser head where two rows of capacitors, one above the other, are utilized on each side of the laser channel. Both the single-deck and the double-decker type laser heads have been built. An EG&G grounded-grid thyratron is used as the switch. By tightly coupling the thyratron to one electrode and locating it an equal distance from both ends of the electrodes, a uniform glow discharge is obtained. Since the excitation in this case is not the traveling-wave type, the pulsewidth is 7.5 nsec as compared with the 2-4 nsec obtained from the usual Blumlein design.² Our laser configuration allows us to set up a cavity with a total reflector at one end and a partially reflecting mirror at the other end. An increase in output power and a decrease in beam divergence are observed in this situation as compared with the case when no output coupler is used. This is in contrast to the case of traveling-wave excitation when most of the energy is derived from one end of the laser.² A plot of efficiency (output energy/input energy per pulse) vs the applied voltage for output mirrors with different reflectivities is shown in Fig. 2 for a single-deck laser. This laser has a gap of 1.5 cm between the electrodes and a total capacitance of 25 nF. When a 4% output coupler is used, this laser has a peak power of 175 kW at 15 kV and 130-Torr N₂ pressure when operating at 20 pulses/sec. The half-angle divergence is 0.7 × 3.5 mrad. These data can be extended to the double-decker laser, which has comparable efficiencies but twice the energy storage capacity. Peak power of 500 kW has been obtained from a double-decker laser with 3-cm gap spacing. The combined features of high power, long pulsewideth, and low divergence make this type of N₂ laser a highly efficient pump for dye lasers. It is also stable, compact, durable, and simple to build. Work is under way to increase the pulse repetition rate. Further technical details will be presented, and limits on the performance and reliability of this type of N₂ laser will be discussed.

© 1976 Optical Society of America