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The output characteristics of a toric unstable resonator fitted to a multichannel stripline excitation system are presented. The resonator is shown to possess the usual advantages of a conventional unstable resonator plus the ability to modify the profile of the output beam by a simple change in the coupling aperture. Laser output parameters have been studied as a function of coupling fraction, magnification, and internal loss factors. Variations in the focal spot size as a function of the coupling aperture as well as resonator alignment sensitivity and polarization properties have been investigated.

An electronic laser controller, based on a computer vision system, has been developed for automatic mode and power control of a high powered CO(2) laser. The cross-sectional image of a sample of the output beam is continually analyzed and used to servo regulate both the laser cavity and the excitation level of the discharge. The technique stabilizes average laser output power to within 4%, while maintaining the best output power distribution achievable by the particular laser. Control system design also provides important on-line beam intensity profile data to assist in maximization of operating efficiency.

The design, construction, and operational characteristics of an optical resonator for an annular gain media are described. The system, developed for laser power extraction investigations in a new type of coaxial discharge geometry, features a folded multipass unstable resonator concept, fabricated from lightweight uncoated diamond-turned aluminum substrates. The resulting cw CO2 device incorporates excitation aspects of the nonself-sustained PIE excitation process in addition to a new magnetic discharge stabilization technique. Laser performance and output beam characteristics are presented.

The optical performance of a cw PIE CO(2) laser has been substantially improved through the adoption of a burst-mode gain switching technique. The approach has provided a doubling of the average beam power extractable from the device. With appropriate optimization, the process could possibly permit the attainment of pulsed energy extraction in the kilohertz range, and with average optical powers within the several tens of kilowatt category.

A theoretical investigation of a stable concave-convex resonator configuration, which appears suitable for single-mode high-power energy extraction from large volume gain media, is presented. The design features annular output coupling with a surprisingly uniform near-field intensity distribution. The computer-based analysis, supported by preliminary experimental results, suggests that acceptable alignment tolerances are provided along with an unusually small beam divergence. With proper design, a far-field divergence of 0.5 mrad, encompassing near 80% of the total laser energy, appears feasible. Operational data, recently obtained with this optical extraction approach, have revealed a further important practical advantage over an unstable resonator, being far less prone to mode degradation and hot spot formation on optical component misalignment.