Shuzhen Cui

170 W, single-frequency, single-mode, linearly-polarized, Yb-doped all-fiber amplifier.

A 170 W all-fiber linearly-polarized single-frequency sing-mode ytterbium amplifier at 1064 nm with an optical efficiency of 80% is demonstrated. 3.9 m long ytterbium-doped polarization maintaining fiber with a core diameter of 10 μm is used as the gain fiber, which guarantees a diffraction-limited output with a measured M(2) of 1.02. To suppress the stimulated Brillouin scattering, longitudinally varied strains are applied on the gain fiber according to the signal power evolution and the temperature distribution. 7 times increase of the stimulated Brillouin scattering threshold is achieved.

Integrated ytterbium-Raman fiber amplifier.

An integrated ytterbium-Raman fiber amplifier architecture is proposed for power scaling of a Raman fiber laser. It is an ytterbium (Yb) fiber amplifier seeded with a double or multiple wavelength laser and followed by a passive Raman fiber. The bluest wavelength light gets amplified in the Yb fiber and the power is transferred to redder wavelengths in the following Raman fiber. A proof of principle experiment demonstrates a 300 W all-fiber linearly polarized single mode amplifier at 1120 nm with an optical efficiency of 70%, limited only by available pump power. The amplifier consists of 4 m of Yb-doped fiber and 20 m of germanium-doped fiber, and seeded with a laser emitting at 1070 and 1120 nm. The power evolution of the 1070 and 1120 nm light inside the amplifier is investigated, both numerically and experimentally. The possibility of power scaling to over kilowatt levels is discussed.

Nearly-octave wavelength tuning of a continuous wave fiber laser

The wavelength tunability of conventional fiber lasers are limited by the bandwidth of gain spectrum and the tunability of feedback mechanism. Here a fiber laser which is continuously tunable from 1 to 1.9 μm is reported. It is a random distributed feedback Raman fiber laser, pumped by a tunable Yb doped fiber laser. The ultra-wide wavelength tunability is enabled by the unique property of random distributed feedback Raman fiber laser that both stimulated Raman scattering gain and Rayleigh scattering feedback are available at any wavelength. The dispersion property of the gain fiber is used to control the spectral purity of the laser output.

All-fiber single-mode actively Q-switched laser at 1120 nm.

An all-fiber single-mode actively Q-switched laser at 1120 nm is demonstrated. The laser cavity consists of a 5 m long Yb-doped polarization maintaining gain fiber, an acousto-optical modulator and a pair of FBGs. At a pump power of 2.5 W, a peak power of 0.8 kW is achieved with a pulse duration of 140 ns at a repetition rate of 1 kHz. A slope efficiency of 16.9% with respect to launched pump power is obtained at 10 kHz. The low achievable gain at 1120 nm, imposed by the parasitic lasing limit at conventional Yb lasing wavelength, has a major role in laser performance.

Over 50 W 589 nm single frequency laser by frequency doubling of single Raman fiber amplifier

300 W CW linearly-polarized 1120 nm laser is achieved with an integrated Yb-Raman fiber amplifier. 86 W 1178 nm single frequency Raman fiber amplifier is generated and frequency doubled to 589 nm with power up to 52.7 W.

Sodium guide star laser pulsed at Larmor frequency

589 nm lasers pulsed at Larmor frequency, several hundreds of kilohertz, can increase the brightness of a sodium guide star and are required in remote magnetometry with mesospheric sodium. By amplification of a continuous-wave single-frequency 1178 nm laser in a pulse-pumped Raman fiber amplifier and frequency doubling in an external cavity, high-power pulsed 589 nm laser at Larmor frequency is obtained for the first time, to the best of our knowledge. The pulse format is mainly determined by the 1120 nm Raman pump laser, whose pulse repetition rate and duty cycle are adjustable. Active pulse shaping is applied to minimize the relaxation spike at the leading edge of the pulses. A reduction in pulse width and conversion efficiency from 1120 to 1178 nm is observed in the backwardly pumped Raman fiber amplifier due to the pump pulse transition effect. A 589 nm laser pulsed at a 350 kHz repetition rate and 20% duty cycle with average power up to 17 W is demonstrated as an operation example intended for a geomagnetic field of 0.5 G.

High order cascaded Raman random fiber laser with high spectral purity

An up to 8th order cascaded Raman random fiber laser with high spectral purity is achieved with the pumping of a narrow linewidth amplified spontaneous emission source. The spectral purity is over 90% for all the 8 Stokes orders. The highest output power is 6.9 W at 1691.6 nm with an optical conversion efficiency of 21% from 1062.0 nm. As a comparison, with conventional FBG-based fiber oscillator as pump source, only 47% spectral purity is achieved at 8th order. The temporal stability of the pump laser is proved to play a key role, because the time fluctuation of pump laser is transferred directly to Raman outputs and results in power distribution among different Stokes orders.

Sodium guide star laser pulsed at Larmor frequency: erratum

We correct an improper statement on the geomagnetic field of an astronomical telescope site in our original paper [Opt. Lett.42, 4351 (2017)OPLEDP0146-959210.1364/OL.42.004351].

Stimulated-Brillouin-scattering suppression in high power single frequency fiber amplifiers

We report our recent works on suppression of stimulated-Brillouin-scattering in high power, single frequency, linearly polarized, 1178 nm Raman fiber amplifiers and 1064 nm ytterbium-doped fiber amplifiers by applying longitudinally varied strain in the gain fibers.

170 W single-frequency single-mode polarization maintaining fiber amplifier

A 170 W all-fiber linearly-polarized single-frequency sing-mode ytterbium amplifier at 1064 nm with an optical efficiency of 80 % was demonstrated with stimulated Brillouin scattering suppressed by applying longitudinally varying strain on the gain fiber.