An unstable confocal resonator with unitized output coupling

The structure and the output characteristics of an unstable confocal resonator with unitized output coupling were studied in detail. The output power, the electrical-photo conversion efficiency and far-field intensity distribution of high-power transverse flow cw CO₂ laser with unitized output coupling unstable resonator (the geometrical magnification parameter M is equal to 1.5) have been measured. The output power is larger than 1.8 kW; the electrical-photo conversion efficiency is as high as 14% and the far-field divergency (total angle) is about 2 mrad. Control experiments show that under otherwise equal conditions the output power and the efficiency of an unstable resonator with scraper plate coupling are 1.2 kW and 9.2%, respectively.