Characterization of a multi-kW, large-aperture gas-cooled Faraday rotator

Area of Science:

• Optics and Photonics
• Laser Technology
• Materials Science

Background:

• High-energy, high-power laser systems are susceptible to stress-induced depolarization.
• Depolarization degrades laser performance and complicates applications.
• Existing methods for depolarization compensation may be insufficient for large apertures.

Purpose of the Study:

• To characterize a novel large-aperture gas-cooled Faraday rotator (FR).
• To evaluate the FR's effectiveness in mitigating stress-induced depolarization.
• To assess the performance of the FR in a high-power laser environment.

Main Methods:

• The Faraday rotator utilized ceramic TGG material.
• Testing involved a 150 mW probe beam (1047 nm) and a pump beam (1070 nm).
• Performance was evaluated under 3.3 kW of effective pump power using a surrogate depolarization plate.

Main Results:

• The gas-cooled FR successfully compensated for birefringence induced by the depolarization plate.
• It reduced spatially inhomogeneous depolarized light across a 58×58 mm² aperture.
• Residual depolarized energy was reduced to approximately 0.8% (-21 dB), with near-linear polarization states.

Conclusions:

• The large-aperture gas-cooled Faraday rotator is highly effective for depolarization compensation.
• This technology is suitable for mitigating depolarization in demanding high-energy, high-power laser systems.
• The FR ensures improved beam quality and stability in advanced laser applications.