In-fiber waveguide-based mode-locker for generating diverse ultrafast pulses.

Area of Science:

• Nonlinear photonics
• Fiber laser technology
• Ultrafast optics

Background:

• High-performance laser technologies require optimal mode-lockers.
• Market demand exists for integrated and robust saturable absorbers.
• Current solutions face technical complexities in fabrication and integration.

Purpose of the Study:

• To present a novel femtosecond laser-inscribed in-fiber waveguide as a saturable absorber.
• To demonstrate its capability for ultrafast pulse generation.
• To address cost, fabrication, and stability challenges in mode-locker design.

Main Methods:

• Fabrication of a straight waveguide by femtosecond laser inscription, integrating few-mode fiber into single-mode fiber.
• Utilizing nonlinear polarization rotation and multimode interference within the waveguide as a saturable absorber.
• Characterization of pulse generation in both anomalous and normal dispersion regimes.

Main Results:

• Achieved 1.36 ps soliton pulses (2.9 nm bandwidth) at 1573 nm in the anomalous dispersion regime.
• Generated Q-switched mode-locked pulses at 1574 nm (190 mW pump power) in the normal dispersion regime.
• Produced 712 fs noise-like pulses (8 nm bandwidth, 4.57 MHz repetition rate) at 1572 nm (295 mW pump power).

Conclusions:

• The developed waveguide offers a simple, cost-effective, compact, and robust solution for mode-locking.
• Hybrid nonlinear effects in the waveguide facilitate advanced ultrafast pulse generation.
• This advancement holds significant promise for nonlinear optics and photonics.