Enhanced laser performance in an LD end-pumped YAP/Tm:YAP/YAP bonding rod with concave end faces

Area of Science:

• Laser physics
• Materials science

Background:

• Diode-laser (LD) pumped solid-state lasers are crucial for various applications.
• Thulium-doped YAP (Tm:YAP) crystals are promising for near-infrared (NIR) laser generation.
• Thermal lensing and heat dissipation are critical challenges in high-power laser systems.

Purpose of the Study:

• To investigate the combined effects of thermal bonding and concave end faces on the laser performance of 795 nm LD-pumped Tm:YAP crystals.
• To analyze the thermal lensing effect and its compensation using concave end faces.
• To optimize high-power NIR laser output from Tm:YAP crystals.

Main Methods:

• Fabrication of YAP/Tm:YAP/YAP bonding rods with both thermal bonding and concave end faces.
• Experimental characterization of laser output power, slope efficiency, and optical-optical conversion efficiency.
• Analysis of thermal focal length and beam quality factors (Mx²/My²).

Main Results:

• Concave end faces effectively compensated for thermal lensing effects.
• A maximum output power of 42.5 W was achieved with a concave YAP/Tm:YAP/YAP bonding rod (radius of curvature 500 mm).
• This configuration yielded a slope efficiency of 47.4% and an optical-optical conversion efficiency of 41.6%, with beam quality factors of 1.67/1.69.
• Compared to flat end faces, the concave design increased maximum output power by ~16% and improved efficiency by ~4%.

Conclusions:

• The combination of thermal bonding and concave end faces effectively enhances heat dissipation and mitigates thermal lensing in Tm:YAP lasers.
• This approach leads to significantly improved high-performance NIR laser output.
• The findings offer a promising strategy for developing high-power solid-state lasers.