2.8-µm polarization-maintaining Er fiber laser mode-locked by a GaSb-based SESAM

Area of Science:

• Optics and Photonics
• Materials Science
• Laser Physics

Background:

• Mid-infrared fiber lasers are crucial for spectroscopy and sensing.
• Achieving stable mode-locking in these lasers, especially at longer wavelengths, presents significant challenges.
• Semiconductor Saturable Absorber Mirrors (SESAMs) are effective for mode-locking but require optimization for specific spectral regions.

Purpose of the Study:

• To demonstrate continuous-wave picosecond mode-locking of a mid-infrared Er:ZBLAN fiber laser using a Gallium Antimonide (GaSb)-based SESAM.
• To investigate the stability, output power, and tunability of the mode-locked laser system.
• To explore the potential for passively Q-switched operation.

Main Methods:

• Fabrication and integration of a GaSb-based SESAM into an Er:ZBLAN fiber laser cavity.
• Characterization of the laser's mode-locking performance, including output power, repetition rate, and pulse energy.
• Wavelength tuning using an intracavity diffraction grating.
• Assessment of polarization properties and signal-to-noise ratio.

Main Results:

• Stable continuous-wave picosecond mode-locked operation was achieved at 2.76 µm.
• The laser delivered an average output power of 190 mW with a repetition rate of 32.07 MHz and pulse energy of ~6 nJ.
• A high signal-to-noise ratio of ~80 dB and polarization extinction ratio >23 dB were recorded.
• Continuous wavelength tunability was demonstrated from 2.706 µm to 2.816 µm.
• Passively Q-switched operation was also successfully demonstrated.

Conclusions:

• The GaSb-based SESAM effectively enables stable picosecond mode-locking for mid-infrared Er:ZBLAN fiber lasers.
• The developed laser system exhibits excellent stability, high output power, and broad tunability, suitable for various applications.
• This work highlights the potential of SESAMs for advanced mid-infrared laser development.