Frequency-dependent graded reflectivity mirror: characterization and laser implementation

Area of Science:

• Optics and Photonics
• Laser Physics
• Materials Science

Background:

• Traditional laser resonators often employ fixed reflectivity mirrors, limiting control over beam characteristics.
• Variable reflectivity mirrors offer potential for enhanced laser performance and mode control.
• Frustrated total internal reflection (FTIR) and interference effects provide a basis for novel optical components.

Purpose of the Study:

• To theoretically and experimentally investigate a new family of variable reflectivity mirrors.
• To characterize the frequency-dependent reflectivity of these novel mirrors.
• To evaluate the performance of these mirrors as output couplers in a Nd:YAG laser resonator.

Main Methods:

• Theoretical modeling of frustrated total internal reflection and interference effects for mirror design.
• Experimental fabrication and characterization of variable reflectivity mirrors.
• Integration of the mirror as an output coupler in an unstable Nd:YAG laser resonator.
• Comparison of laser performance with standard stable resonator configurations.

Main Results:

• Demonstrated mirrors with significant transverse reflectivity changes (50% power reflectivity change within 8.0 GHz).
• Observed a reduction in beam divergence by over an order of magnitude in an unstable resonator configuration.
• Achieved only a 10% reduction in output power compared to a stable resonator.
• Investigated laser resonator mode competition influenced by frequency-dependent mirror reflectivity.

Conclusions:

• The developed variable reflectivity mirrors offer a promising method for controlling laser beam divergence.
• These frequency-sensitive mirrors enable significant improvements in beam quality with minimal power loss.
• The findings suggest potential applications in advanced laser systems requiring precise mode control.