Tm:CALGO lasers at 2.32 µm: cascade lasing and upconversion pumping.

Area of Science:

• Solid-state laser physics
• Materials science
• Quantum electronics

Background:

• Thulium (Tm³⁺) doped lasers are crucial for mid-infrared applications.
• Disordered crystals offer unique optical properties but face challenges like bottleneck effects.
• CaGdAlO₄ is a novel host material for rare-earth doping.

Purpose of the Study:

• To report the first laser operation of a disordered Tm:CaGdAlO₄ crystal.
• To investigate strategies for overcoming the bottleneck effect in Tm³⁺ lasers.
• To evaluate the potential of Tm:CaGdAlO₄ for generating ultrashort pulses.

Main Methods:

• Direct diode laser pumping at 0.79 µm.
• Exploitation of cascade lasing and dual-wavelength pumping schemes.
• Measurement of excited-state absorption spectra for polarized light.

Main Results:

• Achieved 264 mW output power at 2.32 µm with 22.5% slope efficiency (vs. absorbed pump power).
• Cascade lasing yielded 585 mW at 1.77 µm and 2.32 µm with 28.3% slope efficiency.
• Dual-wavelength pumping resulted in 357 mW output power at 2.32 µm.

Conclusions:

• Disordered Tm:CaGdAlO₄ is a viable gain medium for 2.32 µm laser operation.
• Cascade and dual-wavelength pumping effectively mitigate the bottleneck effect.
• Broadband emission suggests potential for ultrashort pulse generation in the mid-infrared.