Efficient 1.7 µm pumping of 2 µm thulium lasers

Area of Science:

• Laser Physics and Photonics
• Solid-State Laser Technology
• Materials Science

Background:

• Thulium-doped (Tm) solid-state lasers are crucial for various applications, typically pumped by 0.8 µm wavelength diodes.
• Investigating alternative pumping schemes, such as 1.7 µm resonant diode pumping, can potentially enhance laser performance and efficiency.

Purpose of the Study:

• To evaluate the performance of solid-state 2 µm lasers using thulium-doped active media (Tm:YAG, Tm:YAP, Tm:YLF) under 1.7 µm resonant diode pumping.
• To compare the efficiency and operational characteristics with traditional 0.8 µm pumping methods.

Main Methods:

• Experimental investigation of Tm:YAG, Tm:YAP, and Tm:YLF lasers.
• Utilized 1.7 µm resonant diode pumping as the excitation source.
• Measured slope efficiency, beam quality, output power, and thermal load during continuous-wave operation.

Main Results:

• Achieved high slope efficiencies, reaching up to 80% for Tm:YAP and Tm:YLF, approaching the quantum limit.
• Demonstrated stable continuous-wave operation with good beam quality.
• Obtained output powers of up to 6 W for Tm:YAG and Tm:YLF, and 8 W for Tm:YAP.

Conclusions:

• 1.7 µm resonant diode pumping is a highly efficient method for exciting thulium-doped solid-state lasers.
• This pumping scheme bypasses the need for Tm³⁺-Tm³⁺ cross-relaxation, leading to improved efficiency.
• The low thermal load enables stable, high-power, continuous-wave laser operation with excellent beam quality.