Watt-level diode-pumped thulium lasers around 2.3  µm

Area of Science:

• Laser Physics and Photonics
• Materials Science for Optoelectronics
• Mid-Infrared Laser Technology

Background:

• Mid-infrared lasers are crucial for spectroscopy, remote sensing, and medical applications.
• Thulium-doped (Tm3+) crystalline materials offer potential for efficient laser operation in the 2-3 µm range.
• Developing high-power, continuous-wave (CW) lasers in this spectral region remains an active research area.

Purpose of the Study:

• To investigate and report on efficient diode-pumped mid-infrared laser performance.
• To evaluate Tm:LiYF4, Tm:Y3Al5O12 (Tm:YAG), and Tm:YAlO3 (Tm:YALO3) crystals for laser applications.
• To characterize laser output power, efficiency, and beam quality in CW and quasi-CW regimes.

Main Methods:

• Diode pumping of Tm3+ doped laser crystals (Tm:LiYF4, Tm:YAG, Tm:YALO3) at 789 nm.
• Operation in continuous-wave (CW) and quasi-continuous-wave (quasi-CW) laser regimes.
• Characterization of output power, slope efficiency, wavelength, polarization, and beam quality (M²).

Main Results:

• Watt-level CW output power achieved in the 2.2-2.3 µm range (Tm3+ 3H4→3H5 transition).
• A 1.8 at.% Tm:YALO3 laser generated 1.32 W CW output at 2272-2277 nm with 33.1% slope efficiency.
• Quasi-CW operation scaled output peak power to 2.69 W; pump quantum efficiency and heat loading were analyzed.

Conclusions:

• Tm-doped LiYF4, YAG, and YALO3 crystals are efficient gain media for diode-pumped mid-infrared lasers.
• The demonstrated performance highlights the potential of Tm:YALO3 for high-power mid-infrared laser generation.
• Further optimization can enhance efficiency and power scaling for various applications requiring 2-3 µm radiation.