2080 nm long-wavelength, high-power dissipative soliton resonance in a dumbbell-shaped thulium-doped fiber laser

We demonstrate a 2080 nm long-wavelength mode-locked thulium(Tm)-doped fiber laser operating in the dissipative soliton resonance(DSR) regime. The compact all-fiber dumbbell-shaped laser is simply constructed by a 50/50 fiber loop mirror(FLM), a 10/90 FLM, and a piece of large-gain Tm-doped double-clad fiber pumped by a 793 nm laser diode. The 10/90 FLM is not only used as an output mirror, but also acts as a periodical saturable absorber for initiating DSR mode locking. The stable DSR pulses are generated at the center wavelength as long as 2080.4 nm, and the pulse duration can be tunable from 780 to 3240 ps as the pump power is increased. The maximum average output power is 1.27 W, corresponding to a pulse energy of 290 nJ and a nearly constant peak power of 93 W. This is, to the best of our knowledge, the longest wavelength for DSR operation in a mode-locked fiber laser.

Towards visible-wavelength passively mode-locked lasers in all-fibre format

Mode-locked fibre lasers(MLFLs)are fundamental building blocks of many photonic systems used in industrial,scientific and biomedical applications.To date,1–2μm MLFLs have been well developed;however,passively modelocked fibre lasers in the visible region(380–760 nm)have never been reported.Here,we address this challenge by demonstrating an all-fibre visible-wavelength passively mode-locked picosecond laser at 635 nm.The 635 nm mode-locked laser with an all-fibre figure-eight cavity uses a Pr/Yb codoped ZBLAN fibre as the visible gain medium and a nonlinear amplifying loop mirror as the mode-locking element.First,we theoretically predict and analyse the formation and evolution of 635 nm mode-locked pulses in the dissipative soliton resonance(DSR)regime by solving the Ginzburg-Landau equation.Then,we experimentally demonstrate the stable generation of 635 nm DSR mode-locked pulses with a pulse duration as short as~96 ps,a radio-frequency signal-to-noise ratio of 67 dB and a narrow spectral bandwidth of <0.1 nm.The experimental results are in excellent agreement with our numerical simulations.In addition,we also observe 635 nm noise-like pulse operation with a wide(>1 nm)and modulated optical spectrum.This work represents an important step towards miniaturized ultrafast fibre lasers in the visible spectral region.

Chip-scale broadband spectroscopic chemical sensing using an integrated supercontinuum source in a chalcogenide glass waveguide

On-chip spectroscopic sensors have attracted increasing attention for portable and field-deployable chemical detection applications. So far, these sensors largely rely on benchtop tunable lasers for spectroscopic interrogation. Large footprint and mechanical fragility of the sources, however, preclude compact sensing system integration. In this paper, we address the challenge through demonstrating, for the first time to our knowledge, a supercontinuum source integrated on-chip spectroscopic sensor, where we leverage nonlinear Ge_(22)Sb_(18)Se_(60) chalcogenide glass waveguides as a unified platform for both broadband supercontinuum generation and chemical detection. A home-built, palm-sized femtosecond laser centering at 1560 nm wavelength was used as the pumping source. Sensing capability of the system was validated through quantifying the optical absorption of chloroform solutions at 1695 nm. This work represents an important step towards realizing a miniaturized spectroscopic sensing system based on photonic chips.

Visible Raman and Brillouin lasers from a microresonator/ZBLAN-fiber hybrid system

Raman and Brillouin lasers based on a high-quality(high-Q) whispering gallery mode microresonator(WGMR)are usually achieved by employing a tunable single-frequency laser as a pump source. Here, we experimentally demonstrate visible Raman and Brillouin lasers using a compact microresonator/ZrF4-BaF2-LaF3-AlF3-NaF(ZBLAN)-fiber hybrid system by incorporating a WGMR with a fiber-compatible distributed Bragg reflector/fiber Bragg grating to form a Fabry–Perot(F-P) fiber cavity and using a piece of Pr:ZBLAN fiber as gain medium.The high-Q silica-microsphere not only offers a Rayleigh-scattering-induced backreflection to form the ~635 nm red laser oscillation in the F-P fiber cavity, but also provides a nonlinear gain in the WGMR itself to generate either stimulated Raman scattering or stimulated Brillouin scattering. Up to six-order cascaded Raman lasers at0.65 μm, 0.67 μm, 0.69 μm, 0.71 μm, 0.73 μm, and 0.76 μm are achieved, respectively. Moreover, a Brillouin laser at 635.54 nm is clearly observed. This is, to the best of our knowledge, the first demonstration of visible microresonator-based lasers created by combining a Pr:ZBLAN fiber. This structure can effectively extend the laser wavelength in the WGMR to the visible waveband and may find potential applications in underwater communication, biomedical diagnosis, microwave generation, and spectroscopy.

212-kHz-linewidth,transform-limited pulses from a single-frequency Q-switched fiber laser based on a few-layer Bi_2Se_3 saturable absorber

Conventional Q-switched fiber lasers operating at multi-longitudinal-mode oscillation usually suffer from selfmode-locking-induced temporal instability, relatively strong noise, and low coherence. Here, we address the challenge through demonstrating, for the first time, to the best of our knowledge, a single-longitudinal-mode(SLM)Er-doped fiber(EDF) laser passively Q-switched by a few-layer Bi_2Se_3 saturable absorber(SA). The Bi_2Se_3 SA prepared by the liquid-phase exfoliation method shows a modulation depth of ～5% and saturation optical intensity of 1.8 MW∕cm^2. A section of 1-m unpumped EDF together with a 0.06-nm-bandwidth fiber Bragg grating is used as an ultra-narrow autotracking filter to realize SLM oscillation. Stable SLM Q-switching operation at 1.55 μm is successfully achieved with the spectral linewidth as narrow as 212 kHz and the pulse duration of2.54 μs, manifesting near-transform-limited pulses with a time-bandwidth product of 0.53. In particular, we found that the SLM Q-switching possesses the higher signal-to-noise ratios of 62 dB(optical) and 48 dB(radio frequency), exhibiting its advantages of low noise and high stability. Such an SLM Q-switched fiber laser could gain great interest for some applications in coherent detection, coherent optical communications, and high-sensitivity optical sensing.