Enhanced spectral breathing for sub-25 fs pulse generation in a Yb-fiber laser

Abstract

We demonstrate a dispersion-mapped Yb-fiber laser with enhanced intracavity spectral breathing. A staged filtering by dissipation through a 30 nm bandpass filter and nonlinear spectral compression results in a transform-limited narrow bandwidth seed pulse for the amplifier fiber. The pulse evolves in the active fiber without gain bandwidth limitation. Further spectral scaling is achieved by single mode fiber. Simulation predicts an overall spectral breathing ratio of as high as 40. Pulse duration of sub-25 fs with 2.3 nJ pulse energy was achieved in experiment.

Impact of initial pulse shape on the nonlinear spectral compression in optical fibre

“…Moreover, we expect that the present study can support a better understanding of the practical tolerance of multistage fibre amplifier architectures to pulse degradation factors [39] as well as provide a deeper insight into the in-cavity dynamics of mode-locked fibre lasers [40,41]. The proposed approach relying on time-frequency analysis can be naturally extended to the scenarios in which the temporal chirp and/or additional phase corrections [42] are applied to the propagating pulse by a an external phase modulator [43] or through cross-phase modulation [44].…”

Modeling Frequency Comb Sources

“…With the stretched pulse mode-locking, the single pulse energy can be enhanced to more than 10 nJ [85]. The minimum pulse durations of 25 [27] and 37 fs [86] were obtained with single-mode Yb-doped fiber and Er-doped fiber respectively. The minimum pulse durations are both obtained with pulse energy less than 1 nJ.…”

“…Ti:sapphire can provide gain in a wide bandwidth spanning several hundreds of nanometers, which can support oscillations of ultrashort pulses even down to a few cycle of optical waves [25,26]. Compared to other laser sources, Ti:sapphire lasers are still preferred in laboratories in nonlinear optics experiments including, but not be limited to, generation of coherent supercontinua and self-referenced optical frequency combs, because of their high power and ultrashort pulsewidth [19,[25][26][27]. Besides Ti:sapphire lasers, KLM solid state lasers based on other gain mediums doped by Nd, Cr, Yb, Tm, and other ions also show high power output but relatively longer pulses [28,29].…”

“…Moreover, because of the large breathing of the pulse power in the cavity, nonlinear phase accumulation is also reduced effectively which in turn enhances the single pulse energy [47,66]. By adopting selfsimilar propagation in the gain fiber and using a nonlinear fiber after the gain fiber to further extend the spectrum to over the gain bandwidth limit, such lasers have generated pulse duration about 20 fs, which is currently the record of ultrashort pulse fiber lasers [19,27,66]. Detail characterizations of such self-similar fiber lasers can be found in [47] and [84].…”

“…Preliminary experiments demonstrates the feasibility by generating 25 and 20 fs pulses directly from stretched pulse [27] and selfsimilar [19] fiber laser cavities respectively. It is expected that the spectral bandwidth can be further enhanced by improved cavity designs.…”