Variable reflectivity unstable resonators for coherent laser radar emitters.

Area of Science:

• Optics and Photonics
• Laser Physics
• Resonator Design

Background:

• Carbon dioxide (CO2) lasers are widely used in industrial and scientific applications.
• The performance of a laser resonator is significantly influenced by the reflectivity profiles of its mirrors.
• Graded reflectivity mirrors (GRMs) offer tunable beam profiles compared to traditional uniform reflectivity mirrors.

Purpose of the Study:

• To compare the beam properties of a TE CO2 laser.
• To evaluate the impact of different graded reflectivity mirror couplers on beam characteristics.
• To determine the suitability of various mirror configurations for coherent ladar applications.

Main Methods:

• Experimental setup utilizing a TE CO2 laser.
• Implementation of a Cassegrain resonator configuration.
• Employing various graded reflectivity mirror couplers with distinct profiles (Gaussian and parabolic).
• Characterization of near-field and far-field beam properties.

Main Results:

• Gaussian profiles experimentally maximized far-field intensity.
• Parabolic profiles resulted in more uniform near-field beam distributions.
• Parabolic profiles exhibited lower energy extraction efficiency compared to Gaussian profiles.
• Both Gaussian and parabolic mirror configurations demonstrated suitability for coherent ladar.

Conclusions:

• The choice of mirror coupler profile in a Cassegrain resonator impacts CO2 laser beam characteristics.
• Gaussian mirrors are optimal for maximizing far-field intensity, crucial for long-range applications.
• Parabolic mirrors provide beam uniformity in the near-field, potentially beneficial for specific imaging tasks.
• Both mirror types show promise for coherent ladar systems, with selection depending on specific system requirements.