1. Field of the Invention
The present invention relates to specially shaped electrodes for producing a very uniform electric field, especially as used to create an electric discharge to excite gas lasers.
2. Description of the Prior Art
Specially shaped electrodes for generating a uniform electric field throughout a specified region of space are required in many applications. An especially important application is the generation of uniform, large volume, pulsed electrical discharges in transversely excited gas lasers. Other applications include designing high-voltage components and measuring the breakdown field strength of gases.
A transversely excited gas laser is a gas laser excited by an electric discharge arising from a transverse electric field between a pair of electrodes disposed on opposite sides of a gas-filled laser cavity. It is well known that the electric field strength between the electrodes should be as uniform as possible throughout the region in which the electric discharge is to occur in order to achieve high laser conversion efficiency and a spatially uniform output beam.
Because of fringe effects near the edges of flat electrodes, all known electrode designs for achieving a uniform electric field strength throughout a predetermined region require the electrodes to extend considerably beyond the region. Unfortunately, extending the electrodes lessens the compactness of the apparatus and, even more importantly, increases the inductance of the electrodes, thereby lengthening the rise and fall times of electrical current pulses applied thereto. This reduces the conversion efficiency of lasers, such as excimer lasers, whose gain media have relatively short lifetimes in their excited state.
To avoid the disadvantages of overly extended electrodes, most prior art designs adhere to a chosen theoretical contour in the central region of the electrode and then truncate or round off the edges of the electrode at some empirically determined point. This results in a degradation in the uniformity of the electric field which is difficult to predict analytically and must be overcome by modifying the electrode shape by laborious trial and error.