In-band pumped Kerr-lens mode-locked Tm,Ho-codoped calcium aluminate laser

Area of Science:

• Lasers and Photonics
• Solid-State Physics

Background:

• Thulium (Tm) and Holmium (Ho) doped lasers are crucial for applications in the ~2 µm spectral region.
• Achieving efficient mode-locking in these systems, particularly with in-band pumping, presents significant challenges.

Purpose of the Study:

• To demonstrate the first in-band pumped Kerr-lens mode-locked Tm,Ho solid-state laser operating at ~2 µm.
• To investigate the performance characteristics, including pulse duration and output power, of such a laser system.

Main Methods:

• Utilized a Tm,Ho,Lu-codoped calcium aluminate (CaGdAlO4) crystal as the gain medium.
• Employed in-band pumping of Tm ions using a 1678 nm Raman fiber laser.
• Implemented soft-aperture Kerr-lens mode-locking to generate ultrashort soliton pulses.

Main Results:

• Generated soliton pulses as short as 79 fs at a central wavelength of 2073.6 nm.
• Achieved an average output power of 91 mW at a pulse repetition rate of ~86 MHz.
• Scaled average output power to 842 mW with slightly longer pulses (155 fs) at 2045.9 nm, corresponding to a peak power of ~58 kW.

Conclusions:

• Successfully demonstrated the first in-band pumped Kerr-lens mode-locked Tm,Ho solid-state laser at ~2 µm.
• The use of a structurally disordered CaGdAlO4 host codoped with Lu broadened the emission line, facilitating ultrashort pulse generation.
• The results highlight the potential of this laser architecture for generating high-power, ultrashort pulses in the ~2 µm range.