Xuezong Yang

Ultra-wide wavelength tuning of a cascaded Raman random fiber laser

An ultra-broadband tunable cascaded Raman random fiber laser pumped by a tunable (1020-1080 nm) ytterbium-doped fiber laser is investigated. By continuously adjusting the pump laser wavelength, the Raman random laser tunes accordingly due to the Raman gain competition. By increasing the pump power, up to the 5th order Raman random laser is achieved. As a result, 300 nm of continuous wavelength tuning from 1070 to 1370 nm is achieved by adjusting the pump wavelength and power altogether. The highest output power is 1.8 W at 1360 nm with an optical efficiency of 15% from 1080 nm. To the best of our knowledge, this is the widest wavelength tuning range reported for a random fiber laser so far.

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.

Actively mode-locked Raman fiber laser

Active mode-locking of Raman fiber laser is experimentally investigated for the first time. An all fiber connected and polarization maintaining loop cavity of ~500 m long is pumped by a linearly polarized 1120 nm Yb fiber laser and modulated by an acousto-optic modulator. Stable 2 ns width pulse train at 1178 nm is obtained with modulator opening time of > 50 ns. At higher power, pulses become longer, and second order Raman Stokes could take place, which however can be suppressed by adjusting the open time and modulation frequency. Transient pulse evolution measurement confirms the absence of relaxation oscillation in Raman fiber laser. Tuning of repetition rate from 392 kHz to 31.37 MHz is obtained with harmonic mode locking.

Broadband tunable InAs/InP quantum dot external-cavity laser emitting around 1.55 μm

We report a broadband tunable external-cavity laser based on InAs/InP quantum dots (QDs) grown by metal-organic vapor phase epitaxy. It is found that high AsH₃ flow during the interruption after QD deposition greatly promotes QD ripening, which improves the optical gain of QD active medium in lower energy states. Combined with anti-reflection/high-reflection facet coatings, a broadly tunable InAs/InP QD external-cavity laser was realized with a tuning range of 140.4 nm across wavelengths from 1436.6 nm to 1577 nm at a maximum output power of 6 mW.

High-Power Single-Frequency 1336 nm Raman Fiber Amplifier

A high power, single frequency, quasi-continuous-wave 1336 nm laser is achieved by Raman amplification of an external cavity diode laser in a variably strained polarization maintaining silica fiber. The pump laser is a 1256 nm Ytterbium-Raman integrated fiber amplifier with a maximum output peak power of 235 W. The 1336 nm amplifier produces square-shaped pulses with tunable repetition rate and duration. The peak power is as high as 53 W, which remains constant during the tuning. A polarization extinction ratio of >25 dB is achieved due to the all polarization maintaining fiber configuration. The laser is locked precisely at 1336.63 nm for future application in laser cooling of 27Al+ after 8th harmonic generation.

High performance 2150 nm-emitting InAs/InGaAs/InP quantum well lasers grown by metalorganic vapor phase epitaxy

We demonstrate high performance 2150 nm InAs/InGaAs/InP quantum well (QW) lasers grown by metalorganic vapor phase epitaxy. The laser structure consists of two InAs/InGaAs QWs, with a 30 μm-wide ridge waveguide and two cleaved cavity facets. The continuous wave operation at room temperature (RT) is achieved, with an output power of larger than 160 mW per facet and with a low threshold current density of 90.4 A/cm(2) per QW derived for the infinite cavity length. Under pulse injection mode, the maximal peak power per facet is as high as 1.35 W. By varying the cavity length, the lasing wavelength can be tuned in a range from 2142 nm to 2154 nm. Moreover, the highest operating temperature reaches up to 100 °C, and characteristic temperatures are 50 K (T(0)) and 132 K (T(1)) in the temperature range of 20-70 °C, respectively.

Raman dissipative soliton fiber laser pumped by an ASE source

The mode locking of a Raman fiber laser with an amplified spontaneous emission (ASE) pump source is investigated for performance improvement. Raman dissipative solitons with a compressed pulse duration of 1.05 ps at a repetition rate of 2.47 MHz are generated by utilizing nonlinear polarization rotation and all-fiber Lyot filter. A signal-to-noise ratio as high as 85 dB is measured in a radio-frequency spectrum, which suggests excellent temporal stability. Multiple-pulse operation with unique random static distribution is observed for the first time, to the best of our knowledge, at higher pump power in mode-locked Raman fiber lasers.

Mode-Locked Ho3+-Doped ZBLAN Fiber Laser at 1.2 mu m

A mode-locked Ho3+-doped ZBLAN fiber laser at 1.2 μm was demonstrated for the first time employing a nonlinear polarization rotation technique for mode-locking. The laser was pumped at 1137 nm by the Raman fiber laser. Stable dissipative soliton mode-locking was achieved with an intracavity Lyot filter formed from a length of polarization maintaining fiber and a polarization dependent optical isolator. 1.3-nJ pulses with pulse duration of 47 ps at a repetition rate of 1.77 MHz were produced. Multiple pulse operation with burst energy up to 6.7 nJ was observed at higher pump power.

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.

Raman dissipative soliton fiber laser pumped by an ASE source: publisher’s note

This publishers note corrects a typo in the affiliations in Opt. Lett.42, 5162 (2017)OPLEDP0146-959210.1364/OL.42.005162.