Wideband saturable absorption in few-layer molybdenum diselenide (MoSe₂) for Q-switching Yb-, Er- and Tm-doped fiber lasers.

We fabricate a free-standing molybdenum diselenide (MoSe2) saturable absorber by embedding liquid-phase exfoliated few-layer MoSe2 flakes into a polymer film. The MoSe2-polymer composite is used to Q-switch fiber lasers based on ytterbium (Yb), erbium (Er) and thulium (Tm) gain fiber, producing trains of microsecond-duration pulses with kilohertz repetition rates at 1060 nm, 1566 nm and 1924 nm, respectively. Such operating wavelengths correspond to sub-bandgap saturable absorption in MoSe2, which is explained in the context of edge-states, building upon studies of other semiconducting transition metal dichalcogenide (TMD)-based saturable absorbers. Our work adds few-layer MoSe2 to the growing catalog of TMDs with remarkable optical properties, which offer new opportunities for photonic devices.EJRK and TH acknowledge support from the Royal Academy of Engineering (RAEng), through RAEng Fellowships.This is the author accepted manuscript. The final version is available from the Optical Society of Amercia via http://dx.doi.org/ via http://dx.doi.org/10.1364/OE.23.02005

Seeded optical parametric generation in CdSiP2 pumped by a nanosecond pulsed, MHz repetition rate Raman fiber amplifier at 1.24 µm

We report a CdSiP2 (CSP) based seeded optical parametric generator (OPG), emitting sub-nanosecond duration, 3 MHz repetition rate, wavelength tunable mid-infrared (MIR) light at 4.2-4.6 μm. We generate up to 0.25 W at 4.2 μm with a total pump conversion efficiency of 42%. The OPG is pumped by a 1.24 μm Raman fiber amplifier system. This is the first demonstration of pumping CSP with a Raman fiber source in this region, and we show that Raman fiber sources in the near-infrared (NIR) are ideal pump sources for non-critically phasematched (NCPM) CSP devices. Pumping CSP at 1.24 μm permits the use of NCPM whilst decreasing the negative effects of both two-photon absorption and linear absorption losses, when compared to conventional 1 μm pumping. This offers a potential advantage for MIR power scaling of CSP parametric devices due to a reduced thermal load in the crystal from residual pump absorption. The OPG is seeded with a continuous-wave fiber supercontinuum source emitting radiation in the 1.7 μm region, to lower the threshold pump intensity required for efficient conversion. NCPM and temperature tuning of the crystal allow for simple wavelength tuning of the idler radiation. We report on laser damage induced by elevated crystal temperatures, which we propose is linked to the decrease in CSP bandgap energy with increasing temperature

Highly efficient nanosecond 560 nm source by SHG of a combined Yb-Raman fiber amplifier

We demonstrate a nanosecond 560 nm pulse source based on frequency-doubling the output of a combined Yb-Raman fiber amplifier, achieving a pulse energy of 2.0 µJ with a conversion efficiency of 32% from the 976 nm pump light. By introducing a continuous-wave 1120 nm signal before the cladding pumped amplifier of a pulsed Yb:fiber master oscillator power amplifier system operating at 1064 nm, efficient conversion to 1120 nm occurs within the fiber amplifier due to stimulated Raman scattering. The output of the combined Yb-Raman amplifier is frequency-doubled to 560 nm using a periodically poled lithium tantalate crystal with a conversion efficiency of 47%, resulting in an average power of 3.0 W at a repetition rate of 1.5 MHz. The 560 nm pulse duration of 1.7 ns and the near diffraction-limited beam quality (M2≤1.18) make this source ideally suited to biomedical imaging applications such as optical-resolution photoacoustic microscopy and stimulated emission depletion microscopy

High Average Power Second-harmonic Generation of a CW Erbium Fiber MOPA

We report the generation of 28 W of 780 nm radiation with near diffraction limited beam quality (M²≤1.15) by frequency-doubling a continuous-wave (CW) erbium fiber master oscillator power amplifier (MOPA) system in a periodically poled lithium niobate crystal. The second-harmonic generation conversion efficiency reached 45% with no roll-off observed, suggesting that further power scaling should be possible with higher fundamental pump powers. The generated second-harmonic had a 3 dB spectral bandwidth of 0.10 nm. The presented architecture represents a simple and effective route to generating high-brightness radiation around 780 nm

Visible Raman-shifted Fiber Lasers for Biophotonic Applications

The efficient nonlinear conversion of Yb-doped fiber laser systems using a combination of stimulated Raman scattering and second-harmonic generation is an effective method for developing sources for biophotonic applications in the yellow-green spectral region. In this paper, we review recent progress in the development of these sources, compare the relative benefits of differing source architectures and demonstrate STED microscopy using an exemplar source

Wideband saturable absorption in few-layer molybdenum diselenide (MoSe2_{2}) for Q-switching Yb-, Er- and Tm-doped fiber lasers

We fabricate a free-standing molybdenum diselenide (MoSe$_{2}$) saturable absorber by embedding liquid-phase exfoliated few-layer MoSe$_{2}$ flakes into a polymer film. The MoSe$_{2}$-polymer composite is used to Q-switch fiber lasers based on ytterbium (Yb), erbium (Er) and thulium (Tm) gain fiber, producing trains of microsecond-duration pulses with kilohertz repetition rates at 1060 nm, 1566 nm and 1924 nm, respectively. Such operating wavelengths correspond to sub-bandgap saturable absorption in MoSe$_{2}$, which is explained in the context of edge-states, building upon studies of other semiconducting transition metal dichalcogenide (TMD)-based saturable absorbers. Our work adds few-layer MoSe$_{2}$ to the growing catalog of TMDs with remarkable optical properties, which offer new opportunities for photonic devices.EJRK and TH acknowledge support from the Royal Academy of Engineering (RAEng), through RAEng Fellowships.This is the author accepted manuscript. The final version is available from the Optical Society of Amercia via http://dx.doi.org/ via http://dx.doi.org/10.1364/OE.23.02005

Wideband saturable absorption in few-layer molybdenum diselenide (MoSe<inf>2</inf>) for Q-switching Yb-, Er- and Tm-doped fiber lasers

We fabricate a free-standing molybdenum diselenide (MoSe2) saturable absorber by embedding liquid-phase exfoliated few-layer MoSe2 flakes into a polymer film. The MoSe2-polymer composite is used to Q-switch fiber lasers based on ytterbium (Yb), erbium (Er) and thulium (Tm) gain fiber, producing trains of microsecond-duration pulses with kilohertz repetition rates at 1060 nm, 1566 nm and 1924 nm, respectively. Such operating wavelengths correspond to sub-bandgap saturable absorption in MoSe2, which is explained in the context of edge-states, building upon studies of other semiconducting transition metal dichalcogenide (TMD)-based saturable absorbers. Our work adds few-layer MoSe2 to the growing catalog of TMDs with remarkable optical properties, which offer new opportunities for photonic devices

Q-switched fiber laser with MoS<inf>2</inf> saturable absorber

A MoS2-based saturable absorber is fabricated using wet chemistry techniques. We use it to passively Q-switch a fiber laser at 1068 nm

Synchronously coupled fiber lasers and sum frequency generation using graphene composites

Graphene mode-locked and self-sychronized fiber lasers are used for sum- frequency mixing in a graphene-polymer composite