Broadly tunable continuous-wave Tm,Ho:SrF₂ and Tm,Ho:BaF₂ lasers.

Area of Science:

• Materials Science
• Laser Physics
• Spectroscopy

Background:

• Rare-earth doped fluoride crystals are crucial for developing advanced laser systems.
• Efficient energy transfer between dopants is key to optimizing laser performance.
• Understanding spectroscopic properties informs material design for specific wavelengths.

Purpose of the Study:

• To achieve room-temperature, continuous-wave laser operation in Tm³⁺,Ho³⁺-codoped barium fluoride (BaF₂) and strontium fluoride (SrF₂) crystals.
• To characterize the laser performance, including output power, slope efficiency, and threshold.
• To investigate the spectroscopic properties and energy transfer mechanisms within these codoped crystals.

Main Methods:

• Fabrication and characterization of Tm³⁺,Ho³⁺-codoped BaF₂ and SrF₂ crystals.
• Experimental setup for room-temperature continuous-wave laser operation.
• Spectroscopic measurements including luminescence lifetime and stimulated-emission cross-section determination.

Main Results:

• Achieved the first reported room-temperature continuous-wave laser operation at ~2.1 µm using Tm³⁺,Ho³⁺:BaF₂.
• The Tm,Ho:BaF₂ laser produced 160 mW output at 2073 nm with 31.0% slope efficiency and 43 mW threshold.
• Demonstrated continuous wavelength tuning from 2010 to 2090 nm (80 nm tuning range).
• Observed enhanced Tm³⁺ → Ho³⁺ energy transfer in rare-earth clusters.
• Measured a stimulated-emission cross-section of 0.40×10^-20 cm² and a luminescence lifetime of 14.1 ms for Ho³⁺ in BaF₂.

Conclusions:

• Tm³⁺,Ho³⁺-codoped BaF₂ and SrF₂ crystals are promising materials for efficient ~2.1 µm lasers.
• Enhanced energy transfer and favorable spectroscopic properties contribute to the observed laser performance.
• The demonstrated tunability and efficiency open possibilities for applications in spectroscopy, sensing, and medical treatments.