A radio frequency (RF)-excited gas laser produces laser power when a gas medium within the laser is excited by RF power applied between a pair of electrodes. The RF energy is delivered to the laser electrodes by a drive system that includes an RF energy source and a transmission line. The impedance of the gas medium typically is initially 1,000-2,000 ohms before the gas medium in the laser is ignited and approximately 200 ohms after ignition.
One system that overcomes some of the problems of prior art drive systems for RF-excited gas lasers is disclosed in U.S. Pat. No. 4,837,772 (the ′772 patent) to Laakmann. The system shown in the ′772 patent includes a lumped constant matching system connected directly between a transistor of the RF energy source and the laser. In addition, the ′772 patent discloses a coaxial cable connecting the laser to the input of the RF energy source transistor to create a feedback path. Such a system is “self-oscillating” in that the RF energy source transistor will oscillate initially at a frequency that generates the maximum voltage across the laser electrodes to ignite the laser gas and automatically readjusts its frequency via the feedback path to match the resonant frequency of the laser after the gas medium ignites.
Another system for overcoming some of the problems of prior art RF-excited gas lasers is disclosed in U.S. Pat. No. 5,008,894 (the ′894 patent) to Laakmann. The ′894 patent employs a quarter wave coaxial transmission line between the RF energy source and the laser. In addition, the RF energy source includes two transistors in a push-pull configuration that enables the use of a standard 50 ohm transmission line. Such a quarter wave transmission line enhances the break-down of the gas medium, increases laser efficiency, and stabilizes the laser discharge.
Although the systems shown in the ′772 patent and the ′894 patent alleviate some of the impedance matching problems of the prior art, they include oversized circuits with unnecessary complexity for the normal sustained operation after the gas medium in the laser is ignited, such as in a ring laser gyro, thus producing unwanted noise.
Therefore, there exists a need for a simplification of circuitry in a laser and, more particularly, in an electrodeless RF discharge ring laser gyro.