Laser mode locking using a single-mode-fiber coil with enhanced polarization-dependent loss

Area of Science:

• Optics and Photonics
• Fiber Laser Technology

Background:

• Mode-locking is crucial for generating ultrashort laser pulses.
• Polarization-dependent loss (PDL) is a key parameter in laser dynamics.
• Fiber lasers offer advantages in terms of robustness and cost-effectiveness.

Purpose of the Study:

• To demonstrate a novel method for achieving continuous-wave (CW) mode-locking in a thulium-doped all-fiber laser.
• To investigate the use of a passive fiber coil operating in a low-V-number regime to induce polarization-dependent loss (PDL).
• To establish the effectiveness of moderate PDL for stable CW mode-locking.

Main Methods:

• Fabrication and implementation of a passive fiber coil operating in the low-V-number regime.
• Integration of the fiber coil into a thulium-doped all-fiber laser cavity.
• Characterization of the laser output to confirm CW mode-locking operation and assess PDL levels.

Main Results:

• Successful demonstration of CW mode-locking in a thulium-doped all-fiber laser.
• Achieved enhanced bend-induced PDL using a low-V-number fiber coil while maintaining reasonable bend loss.
• Confirmed that a moderate PDL of approximately 1 dB is sufficient for stable CW mode-locking.

Conclusions:

• This study presents the first demonstration of a CW mode-locked fiber laser utilizing PDL generated by a fiber coil.
• The proposed method using a low-V-number fiber coil offers an effective way to achieve and control PDL for laser mode-locking.
• The findings pave the way for developing more robust and efficient fiber laser systems.