Widely tunable 2  μm continuous-wave and mode-locked fiber laser

Area of Science:

• Photonics and Optics
• Laser Physics

Background:

• Thulium-doped fiber lasers are crucial for generating light in the 2-micron spectral region.
• Achieving wide tunability and stable mode-locking in these lasers presents significant challenges.

Purpose of the Study:

• To design and demonstrate a fiber laser with a broad tuning range in both continuous-wave (CW) and passively mode-locked states.
• To investigate the use of nonlinear polarization rotation and a Lyot filter for achieving wide tunability.

Main Methods:

• Utilized a thulium-doped fiber gain medium.
• Employed a nonlinear polarization rotation (NPR) technique for passive mode-locking.
• Incorporated a birefringence Lyot filter as a fiber comb filter to achieve wide wavelength tuning.

Main Results:

• Demonstrated a widely tunable continuous-wave (CW) thulium-doped fiber laser with a tuning range of 127 nm (1823-1950 nm).
• Achieved a single-wavelength mode-locked operation with a tuning range of 94 nm (1835-1929 nm).
• Obtained a dual-wavelength mode-locked operation with a tuning range of 87 nm (1831-1918 nm) at a 3.085 MHz repetition rate and 75 ps pulse width.

Conclusions:

• The proposed laser design successfully achieves wide tunability in both CW and mode-locked regimes.
• The combination of NPR and a Lyot filter is effective for expanding the tuning range of thulium-doped fiber lasers.
• The demonstrated laser offers a versatile platform for various spectroscopic and optical sensing applications.