ASE recirculation effects in pulsed frequency shifted feedback lasers at large frequency shifts

Area of Science:

• * Photonics and Laser Physics
• * Optical Engineering

Background:

• * Explores emission regimes in C-band Er:fiber lasers.
• * Focuses on lasers with frequency-shifted feedback.
• * Investigates phenomena at large frequency shifts.

Purpose of the Study:

• * Clarify the role of amplified spontaneous emission (ASE) recirculation.
• * Analyze spectral and dynamical properties of the laser.
• * Understand Q-switched and modelocked emission characteristics.

Main Methods:

• * Analysis of continuous wave, Q-switched, and modelocked emission.
• * Investigation of ASE recirculation patterns.
• * Application of the moving comb model for ASE recirculation.

Main Results:

• * Q-switched pulses arise from quasiperiodic ASE recirculation and exhibit chirp.
• * Periodic ASE recirculation patterns observed in resonant cavities.
• * Modelocked emission induced under resonant conditions; ASE recirculation coexists with modelocked pulses.
• * Harmonic modelocking observed in non-resonant cavities.

Conclusions:

• * ASE recirculation is a key factor in C-band fiber laser dynamics.
• * Understanding ASE recirculation aids in controlling laser output.
• * The study provides insights into complex laser behaviors like Q-switching and modelocking.