Review of cw high-power CO2 lasers

Various forms of CO₂ lasers have achieved cw powers in the 60 kW range, operating efficiencies approaching 30%, pulse energies of approximately 2000 J, pulse widths less than 1 ns, peak pulse powers in excess of 10⁹ W, a frequency stability of a few parts in 10¹², and sealed-off tube lifetimes of many thousands of hours. In addition, the laser can be easily Q-switched as well as gain-switched and has been electrically, optically, gas dynamically, and chemically pumped. In addition to all these attributes, the CO₂ laser output wavelength lies within one of the best atmospheric windows. It should be no surprise then that during the last eight years, the CO₂ laser has firmly established itself as a candidate for recognition as the most important laser among the numerous laser devices presently known. Depending on the gas pressure, gas flow rate, pumping mechanisms, gas mixture, etc, CO₂ lasers can exhibit a wide range of noise, bandwidth, gain, and power saturation characteristics. This flexibility enables a designer to optimize the performance of CO₂ laser stable-frequency master oscillators; power oscillators; low noise, high-gain pre-amplifiers, intermediate-power or high-power amplifiers. As a result, CO₂ laser oscillator–amplifier chains can be designed utilizing guidelines similar to those which have been extensively applied in the design of transmitters in the rf and microwave region of the electromagnetic spectrum.