High-power fast-axial-flow CO2 laser with a variable-reflectivity output coupler.

Area of Science:

• Optics and Photonics
• Laser Technology
• Materials Science

Background:

• Continuous-wave (cw), direct-current (dc)-excited, fast-axial-flow carbon dioxide (CO2) lasers are crucial for various industrial and scientific applications.
• Improving beam quality and power output in these lasers is an ongoing area of research.

Purpose of the Study:

• To report the development of the first cw, dc-excited, fast-axial-flow CO2 laser incorporating a variable-reflectivity output coupler.
• To demonstrate a method for achieving a high-quality, diffraction-limited laser beam with significant power output.

Main Methods:

• Fabrication of a variable-reflectivity output coupler with a super-Gaussian reflectivity profile (order 8, 96% central reflectivity) using a low-absorption coating on a ZnSe substrate.
• Utilizing an unstable resonator configuration.
• Characterization of the laser output, including power, divergence angle, near-field, and far-field patterns.

Main Results:

• The laser successfully oscillated in the lowest-order mode, producing a diffraction-limited beam.
• Achieved an output power of 300 W with a divergence angle of 0.35 mrad (Full Width at Half Maximum - FWHM).
• Experimental measurements of near-field and far-field patterns closely matched the predictions of the mathematical model.

Conclusions:

• The developed variable-reflectivity output coupler is effective in producing high-quality, high-power beams from fast-axial-flow CO2 lasers.
• The demonstrated technique shows promise for scaling to kilowatt-level power outputs.
• This advancement offers a pathway to more efficient and versatile CO2 laser systems.