C-band wavelength tunable mode-locking fiber laser based on CD-SMS structure

Area of Science:

• Photonics
• Fiber Optics
• Ultrafast Lasers

Background:

• Passively mode-locked fiber lasers are crucial for ultrafast optics.
• Achieving wide wavelength tunability in these lasers remains a challenge.

Purpose of the Study:

• To propose and demonstrate a novel wavelength-tunable passively mode-locked all-fiber laser.
• To utilize a cascaded dual single mode fiber-graded index multimode fiber-single mode fiber (CD-SMS) structure for tunable mode-locking.

Main Methods:

• A CD-SMS structure was designed by fusing two SMS fibers into polarization controller paddles.
• Mode-locking was achieved by controlling nonlinear phase shifts via paddle orientation.
• Wavelength tuning was realized by mechanically adjusting paddle orientation angles.

Main Results:

• Mode-locking was achieved with a pulse duration of 930 fs at 1568 nm.
• A fundamental repetition rate of 18.22 MHz was obtained.
• A 40 nm wavelength tuning range (1533-1573 nm) covering the C-band was demonstrated.

Conclusions:

• The CD-SMS structure effectively enables wavelength-tunable mode-locking in fiber lasers.
• This laser design offers a viable approach for generating tunable ultrafast laser pulses.
• The tuning range is currently limited by the gain bandwidth of erbium ions.