Hybrid mode-locked Er-doped fiber femtosecond oscillator with 156 mW output power

Abstract

We report on an Er-doped fiber oscillator that produces 146 fs pulses with 156 mW average power at a repetition rate of 49.9 MHz. The pulse energy reaches 3.13 nJ, surpassing the conventional power limit in the dispersion-managed soliton regime. Such high pulse power is obtained by devising a hybrid mode-locking scheme that combines saturable absorption with nonlinear polarization evolution. The oscillator also offers excellent temporal purity in the generated pulses with high power, providing a robust fiber-based frequency comb well suited for industrial uses.

Hybrid mode-locked erbium-doped all-fiber soliton laser with a distributed polarizer

“…Nevertheless, stable generation of the shortest pulses can be realized with a hybrid mode-locking technique [14] that implies a co-action of two saturable absorbers-a slow saturable absorber such as SESAM or SWCNTs, and a fast one, such as a nonlinear polarization evolution (NPE) [15] based on the nonlinear Kerr-effect. Owing to the extremely fast nonlinear response of a Kerr-medium (which is ∼10 fs for silica glass [1]) as compared to the SWCNTs recovery time (which is ∼500 fs) USP shaping primarily occurs due to the NPE action in the laser cavity.…”

“…Owing to the extremely fast nonlinear response of a Kerr-medium (which is ∼10 fs for silica glass [1]) as compared to the SWCNTs recovery time (which is ∼500 fs) USP shaping primarily occurs due to the NPE action in the laser cavity. SWCNTs saturable absorber, in turn, not only facilitates mode-locking start-up but also provides a nonlinear filtering and spurious continuous wave (CW) radiation suppression [14], significantly improving laser performance. Commonly the NPE is introduced by means of a combined polarizerisolator embedded into a cavity [14,15].…”

“…SWCNTs saturable absorber, in turn, not only facilitates mode-locking start-up but also provides a nonlinear filtering and spurious continuous wave (CW) radiation suppression [14], significantly improving laser performance. Commonly the NPE is introduced by means of a combined polarizerisolator embedded into a cavity [14,15]. However, in this paper, for the first time to the best of our knowledge, we propose a distributed polarizer based on the short segment PANDA-type birefringent fiber possessing a polarizing effect.…”

Optical Frequency Comb Generation based on Erbium Fiber Lasers

“…Inserting a SESAM into a NPE-based ring laser overcomes some of the limitations and drawbacks of a solely NPE mode-locked laser [133][134][135]. In this configuration, polarization states still must be aligned to benefit from the fast NPE process, however, optimization becomes easier with the SESAM to initiate mode-locking.…”

“…In this configuration, polarization states still must be aligned to benefit from the fast NPE process, however, optimization becomes easier with the SESAM to initiate mode-locking. The SESAM also appears to suppress the long, low power wings in the time domain, providing a cleaner pulse structure [133]. While potentially more robust than lasers that only use NPE, this approach is still incompatible with PM fibers and will still have high environmental sensitivity.…”