Yb,Tm:LiYF₄ lasers at 1.5 and 2.3 µm pumped by a Yb-fiber laser

Area of Science:

• Laser Physics
• Materials Science
• Spectroscopy

Background:

• Developing efficient and scalable laser sources in the 1.5-2.3 µm range is crucial for various applications.
• Thulium (Tm)-doped materials are promising for generating light in these wavelengths but often require specific pumping schemes.
• Yb3+, Tm3+ co-doping offers a potential pathway to leverage established Yb-fiber laser technology for Tm-based emission.

Purpose of the Study:

• To investigate the viability of pumping Yb3+, Tm3+ co-doped crystals using commercial 976 nm Yb-fiber lasers.
• To achieve low-threshold, efficient, and power-scalable laser operation at 1.5 µm and 2.3 µm.
• To characterize the laser performance, including output power, slope efficiency, and threshold, and analyze polarization properties.

Main Methods:

• Utilized a Yb,Tm:LiYF4 crystal as the gain medium.
• Employed a commercial 976 nm Yb-fiber laser for pumping the co-doped crystal.
• Performed continuous-wave (CW) laser operation measurements at 1.5 µm and 2.3 µm.
• Analyzed laser output power, slope efficiency, threshold power, and polarization characteristics.

Main Results:

• Achieved continuous-wave output power of up to 0.70 W at ~2307 nm (³H4→³H5 transition) with a 26.7% slope efficiency and a low threshold of 46 mW.
• Generated 0.60 W of output power at 1497 nm (³H4→³F4 transition) with a 26.1% slope efficiency and a 78 mW threshold.
• Observed linear polarization (π) at 2.3 µm and noted polarization switching (π and σ states) at 1.5 µm, attributed to gain anisotropy.

Conclusions:

• Demonstrated the effectiveness of pumping Yb3+, Tm3+ co-doped crystals with 976 nm Yb-fiber lasers for efficient 1.5 µm and 2.3 µm laser generation.
• The results highlight the potential for power-scalable and low-threshold operation, making this a practical approach for generating light in these important wavelength regions.
• The observed polarization behavior provides insights into the anisotropic gain properties of the Yb,Tm:LiYF4 crystal.