Experimental generation of stable mode-locked pulses and cylindrical vector beams (CVBs), from an all few-mode fiber (FMF) ring laser is first reported, to the best of our knowledge. In this laser, a section of few-mode erbium-doped fiber (FM-EDF) is used as the gain medium. The FM-EDF is pumped by 976 nm laser with LP₁₁ mode, which is simultaneously converted and multiplexed through a homemade hybrid device, i.e., wavelength division multiplexing-mode selection coupler (WDM-MSC). All the components in our experiment are connected using FMF. The resulted CVB pulses have a spectral width of 0.33 nm with a repetition rate of 30.58 MHz under the pump power of 340 mW. Moreover, both azimuthally and radially polarized CVBs were achieved with a high purity of >95%. This mode-locked CVB fiber laser with an all FMF configuration opens the way to manipulate the transverse mode in mode-locked fiber lasers.

We report here an ultra-broadband linearly polarized (LP) LP₀₁ LP₁₁ mode converter operating at 1 μm based on a long period fiber grating (LPFG) fabricated in a conventional two-mode fiber (TMF) by a line-focused CO₂ laser. The measured 3 dB bandwidth is about 240 nm, which is the broadest bandwidth for such fiber mode converters. The maximum conversion efficiency between the LP₀₁ and LP₁₁ modes is >99% over the range of 1000 nm to 1085 nm, almost covering the whole emission band of Yb³⁺, which is useful for further power scaling of high-power fiber lasers operating at the 1 μm band.

We report here on a diode-pumped pulsed mid-infrared laser source based on gas-filled hollow-core fibers (HCFs) towards an all-fiber structure by the tapering method. The pump laser is coupled into an acetylene-filled HCF through a tapered single-mode fiber. By precisely tuning the wavelength of the diode to match different absorption lines of acetylene near 1.5 μm, mid-infrared emission around 3.1–3.2 μm is generated. With 2 m HCFs and 3 mbar acetylene gas, a maximum average power of 130 mW is obtained with a laser slope efficiency of ～24%. This work provides a potential scheme for all-fiber mid-infrared fiber gas lasers.

A passively Q-switched erbium-doped fiber (EDF) laser is proposed and demonstrated utilizing a zirconium disulfide (ZrS₂)-based saturable absorber (SA). ZrS₂ nanosheets are prepared, whose modulation depth, saturation intensity, and nonsaturable absorbance are measured to be 14.7%, 0.34 MW/cm², and 17.4%, respectively. Then, a Q-switched EDF laser is implemented by the ZrS₂-SA. The pulse repetition rate varies from 40.65 to 87.1 kHz when the pump power changes from 55 to 345 mW. The shortest pulse width is 1.49 μs with pulse energy of 33.5 nJ. As far as we know, this is the shortest pulse width obtained by a ZrS₂-SA so far.

We report here a single-pass 1.56 μm fiber gas Raman laser in a deuterium-filled hollow-core fiber and a 2.86 μm cascade fiber gas Raman laser with methane in the second stage. The maximum output powers at 1.56 and 2.86 μm are 27 and 8.5 mW with Raman conversion efficiency of 30% and 42%, respectively. The results offer a new method to produce a 1.5 μm fiber source and prove the potential of the cascade fiber gas Raman laser in extending the available wavelength.

We demonstrate a strain compensated long lifetime semiconductor saturable absorber mirror (SESAM) with a high modulation depth for fiber lasers. The SESAM was measured to have a damage threshold of 9.5 mJ/cm², a modulation depth of 11.5%, a saturation fluence of 39.3 μJ/cm², and an inversed saturable absorption coefficient of 630 mJ/cm². The SESAM has been applied to a linear cavity mode-locked Yb-doped fiber laser, which has been working for more than a year without damage of the SESAM.

A large-mode-area (LMA) ytterbium-doped photonic crystal fiber (PCF) with core NA of 0.034 and core diameter of 50 μm was made by the stack-and-draw technique. The core is formed by Yb³⁺/Al³⁺/F /P⁵⁺ co-doped silica glass containing 0.09 mol% Yb₂O₃ with an absorption coefficient at 976 nm up to 3.2 dB/m. The core glass with homogeneous distribution of Yb³⁺ ions and refractive index difference of 4 × 10 ⁴ compared with pure silica was prepared by the sol-gel method and heat homogenization at 2000°C. Laser power amplification of this LMA PCF was studied using a seed source of 21 ps pulse duration and 48.7 MHz repetition rate at 1030 nm wavelength. With pump power of 520 W, a maximum 272 W (266 kW peak power) quasi-single-mode laser output with M² of 2.2 was achieved in a 4.7 m fiber length bent at a diameter of 47 cm with slope efficiency of 52%, and no obvious mode instability, stimulated Raman scattering, or thermal damage on the end facet of the fiber were observed.

We demonstrate here an environmentally stable and extremely compactable Er-doped fiber laser system capable of delivering sub-100-fs temporal duration and tens of nanojoules at a repetition rate of 10 MHz. This laser source employs a semiconductor saturable absorber mirror mode-locked soliton laser to generate seed pulses. A single-mode-fiber amplifier and a double-cladding-fiber amplifier (both with double-pass configuration) are bridged by a divider and used to manage the dispersion map and boost the soliton pulses. By using 64 replicas, pulses with as high as 60 nJ energy within 95 fs duration are obtained at 10 MHz, corresponding to 600 kW peak power.

We demonstrate an all-fiber Yb:fiber frequency comb with a nonlinear-amplifying-loop-mirror-based Yb:fiber laser oscillator. The fiber-spliced hollow-core photonic bandgap fiber was used as dispersion compensator, which was also directly spliced to a piece of tapered photonic crystal fiber for an octave-spanning spectrum. The spectrum of the compressed 107 fs laser pulses was broadened, covering 600 nm to 1300 nm in a high-nonlinearity tapered fiber for f to 2f beating. The signal-to-noise ratio of offset frequency was measured to be 22 dB.

We demonstrate a 0.95 GHz repetition rate fully stabilized Yb:fiber frequency comb without optical amplification. Benefitting from the high mode power and high coherence, this comb achieved 35 to 42 dB signal to noise ratio on the direct heterodyne beat signals with at least six continuous wave lasers (at 580, 679, 698, 707, 813, and 922 nm) while keeping >40 dB carrier envelope frequency signal. It can be used for the direct measurement of optical frequencies at visible and near-infrared wavelengths and has great potential on simultaneous comparison of multiple optical frequencies.