Mode-locked Yb-doped fiber laser emitting broadband pulses at ultralow repetition rates

CPA-ready femtosecond pulses at 1 MHz from a custom recycled output Mamyshev oscillator

A cost-effective fiber laser architecture is introduced in which the output seed pulse is stretched and then returned in the oscillator for an additional single-pass amplification without spectral broadening. It is implemented in an all-PM-fiber configuration based on a Mamyshev oscillator with a low repetition rate of 1 MHz. It features a linear oscillator bounded by two offset chirped fiber Bragg gratings accompanied by a third one acting as a pulse recycling filter. The latter tailors the pulse profile in amplitude and phase to seed femtosecond chirped-pulse amplification systems without additional pre-amplification nor pulse stretching. A single-pump prototype generating 200-nJ, 100-ps pulses compressible to 290 fs at 1030 nm and at 960 kHz is demonstrated. Furthermore, simulations show how this new oscillator architecture can provide tailored seed pulses with high enough spectral energy density and low enough nonlinear phase to generate sub-200 fs, 40 µJ, > 180 MW pulses from an all-fiber setup involving a single tapered-fiber power amplifier, without pulse picking.

Gain-managed nonlinear amplification of ultra-long mode-locked fiber laser

In this study, we explored the gain-managed nonlinear (GMN) amplification of ultra-low repetition rate pulses in the range of less than 1 MHz. By seeding the developed 1040 nm ultralong fiber modelocked laser to the GMN amplifier, we achieved high gain and boosted the nonlinear pulse propagation effects. We demonstrated that GMN amplification of low repetition rate pulses provided amplification exceeding 32 dB and spectral broadening up to 91 nm at relatively low pump power levels. Achieving broadband 57 fs pulses with energy exceeding 55 nJ suggests that ultralong fiber lasers paired with GMN amplifiers can be effectively utilized as powerful tools for generating femtosecond broadband pulses at ultra-low repetition rates, with controllable spectral characteristics.

Generation of 99.8 fs, 25 kW Peak-Power, Dispersion-Managed Pulses Directly from an Yb-Doped Figure-of-9 Fiber Laser

We reported on the generation of 99.8 fs, 25 kW peak-power, dispersion-managed pulses directly from a passively mode-locked Yb-fiber laser oscillator with a figure-of-9 configuration. The introduction of strongly injected pump power and optical components with a high damage threshold enables high-power operation, while the polarization-maintaining (PM) fiber supports environmentally stable self-started mode-locking. Mode-locking in the soliton-like and negative-dispersion regime is characterized by the dispersion management via tuning the separation distances between a pair of gratings inside the cavity. The oscillator generates stable pulses with up to 40.10 mW average power at a 16.03 MHz repetition rate, corresponding to a pulse energy of 2.5 nJ. To the best of our knowledge, it is the highest peak-power directly obtained by a laser oscillator with a figure-of-9 configuration.

Promotion of pulse peak power by halving the repetition rate based on a vector soliton

We report on an all-fiber mode-locked repetition-rate-switch pulse operation in a Yb-doped fiber laser based on a polarization rotation vector soliton. The polarization controller (PC) in a fiber loop and a polarization-dependent isolator at the output port are incorporated into the laser resonator at the switch of the repetition rate. By adjusting the PC in the cavity, the mode locking can be switched between the fundamental repetition rate and half of it with a tiny pulse width change. Also, the halved pulse exhibits unique properties: a huge promotion in energy and peak power. To the best of our knowledge, this is the first all-fiber seed source with a passive switch of the repetition rate based on a vector soliton.

Highly-stable mode-locked PM Yb-fiber laser with 10 nJ in 93-fs at 6 MHz using NALM

We demonstrate highly stable mode-locked Yb-doped fiber oscillators using a nonlinear amplifying loop mirror, delivering linearly polarized laser pulses with high energy at a low repetition rate of several MHz. These lasers are composed of polarization-maintaining fibers and fiber-based components without intra-cavity dispersion compensation. The spectral and temporal characteristics are systematically investigated at different repetition rates. Spectral bandwidth of 31 nm is realized in the case of 6 MHz repetition rate, and the pulse energy reaches 10 nJ. A pair of gratings compresses the output pulse to 93 fs. RMS power stability is as low as 0.04% in 10 hours, which shows excellent stability. We believe that this type of fiber oscillator is an ideal seed for further high power amplification.

All-fiber polarization-maintaining erbium-doped dispersion-managed fiber laser based on a nonlinear amplifying loop mirror

In this paper, we build a mode-locked all-polarization-maintaining figure-of-8 erbium-doped fiber oscillator based on a nonlinear amplifying loop mirror. The fiber oscillator can generate 1.6 ps chirped pulses that can be de-chirped to 500 fs at 1550 nm with a pulse energy of 0.8 nJ and a repetition rate of 12 MHz. It can be further amplified up to 10 nJ and compressed down to 100 fs with a pre-chirp managed nonlinear amplification setup. Such an oscillator and amplifier configuration has the advantages of self-starting and long-term operation, and it is highly suitable for subsequent frequency conversion, which is desirable for many applications in ultrafast microscopy and precision spectroscopy.