Direct generation of 2 W average-power and 232 nJ picosecond pulses from an ultra-simple Yb-doped double-clad fiber laser.

We report the generation of 2.06 W average-power and 232 nJ picosecond mode-locked pulses directly from an ultra-simple Yb-doped fiber laser. A section of Yb-doped double-clad fiber pumped by a 976 nm laser diode provides the large gain, and the linear cavity is simply formed by a 1064 nm highly reflective fiber Bragg grating and a fiber loop mirror (FLM) using a 5/95 optical coupler. The asymmetric FLM not only acts as the output mirror for providing ∼20% optical feedback, but also equivalently behaves as a nonlinear optical loop mirror (NOLM) to initiate the mode-locking operation in this cavity. Stable mode-locking is therefore achieved over a pump power of 3.76 W. The mode-locked pulses show the dissipative soliton resonance (DSR), which has the pulse duration of 695 ps to ∼1 ns, and the almost unchanged peak power of ∼200 W as increasing the pump power. In particular, this laser can emit 232 nJ high-energy DSR pulses with an average output power of >2 W. This is, to the best of our knowledge, the first demonstration of such an ultra-simple, mode-locked fiber laser that enables watt-level, high energy, picosecond DSR pulses.

Intermode beating mode-locking technique for O-band mixed-cascaded Raman fiber lasers.

A novel intermode beating mode-locking (IBML) technique combined with a cascaded Raman process is proposed to mode-lock an O-band two-cascaded Raman fiber laser. Using a 980-m-long phosphosilicate fiber pumped by a 1064 nm laser, the second-order Raman oscillation at 1319 nm is generated by the mixed-cascaded Raman shifts of P2O5 and SiO2. By precisely matching the intermode beating frequencies of the 1064 nm pump laser and the second-order Raman cavity frequency, harmonic mode-locking at 1319 nm is initiated. The dynamic process of the IBML operation in the cascaded Raman laser is experimentally investigated. The 131st-order harmonic mode-locking with a repetition rate of 27.247 MHz is very stable with the radio-frequency (RF) signal-to-noise ratio of >56 dB and the RF supermode-suppression ratio of >43 dB. The mode-locked pulses with the square profile are confirmed as the noise-like pulses by an autocorrelator. The IBML technique, in combination with the cascaded Raman process, could offer an exciting new prospect for obtaining simple, compact, and arbitrary-wavelength mode-locked laser sources.

Large-energy, wavelength-tunable, all-fiber passively Q-switched Er:Yb-codoped double-clad fiber laser with mono-layer chemical vapor deposition graphene.

We demonstrate a large-energy, wavelength-tunable, all-fiber passively Q-switched Er:Yb-codoped laser using a mono-layer chemical vapor deposition (CVD) graphene saturable absorber (SA). By exploiting the large laser gain of Er:Yb double-clad fiber and optimizing the coupling ratio of the output coupler, not only can the mono-layer CVD graphene SA be protected from oversaturation and thermal damage, but also a large pulse energy up to 1.05 µJ (corresponding to the average output power of 25.6 mW) is thus achieved. Using a tunable fiber Fabry-Perot filter, stable Q-switched pulses can operate with a tunable range from 1530.97 to 1546.92 nm, covering a wavelength range of ∼16 nm. The Q-switching states at the different lasing wavelengths have been observed and recorded. The Q-switched repetition rate and the pulse duration (with the minimum one of 2.6 µs) have been characterized as well. This is, to the best of our knowledge, the largest pulse energy from an all-fiber graphene Q-switched laser.