Narrow-linewidth widely tunable hybrid Q-switched double-clad fiber laser

A laser-diode-pumped Yb-doped double-clad fiber laser operating in a hybrid Q-switched regime has been demonstrated. With pulsed pump light and stimulated Brillouin scattering of the gain fiber as the Q-switching mechanisms, the laser generated nanosecond pulses with a stable repetition rate. A single-pulse energy of as much as 143.1 microJ with a peak power of 28.6 kW was obtained. Use of an external-cavity diffraction grating in the Littman configuration permitted tuning of the laser wavelength over a 15.7-THz range from 1080 to 1140 nm, and a linewidth of 0.04 nm over the whole tuning range was achieved.     

可调脉冲宽度的调Q掺铥双包层光纤激光器

在激光器输出平均功率一定的情况下,峰值功率主要取决于调制频率和脉冲宽度。这使得脉冲宽度的调节具有一定的实际应用价值。对调Q掺铥双包层光纤激光器进行研究,首先确定了激光器的最佳输出透过率,在65%最佳透过率时,得到2 m激光的输出功率3.9 W,斜率效率为31%。外接一个信号发生器,信号门宽从12 s变化到18 s,并测量了调制频率分别在30 kHz、40 kHz和50 kHz时输出脉冲宽度的变化情况,得到了555.6 W的最高峰值功率,实现了脉冲宽度从163.4 ns到207.9 ns的变化。实验情况证实了用外接信号发生器能有效控制激光器的输出脉冲宽度。     

Compact diode-pumped passively Q-switched tunable Er-Yb double-clad fiber laser

Efficient repetitive passive Q switching of a cladding-pumped Er-Yb fiber laser has been demonstrated by use of an external-cavity configuration containing a Co(2+): ZnS crystal as a saturable absorber. Energies of as much as 60muJ in pulses of durations as short as 3.5 ns (FWHM), corresponding to a peak power of >10kW, have been generated, and the maximum slope efficiency with respect to the absorbed pump power was 13%. Using a bulk diffraction grating in the Littrow configuration to provide wavelength-selective feedback, we tuned the passively Q -switched fiber laser over 31 nm from 1532 to 1563 nm. The prospects for further improvement in performance are discussed.     

Tunable and high-energy Q-switched operation of an alexandrite slave ring laser

Narrow bandwith tunable Q-switched operation of an alexandrite oscillator was used for injection-locking of a high-energy alexandrite slave ring laser. Pulses with up to 600 mJ in energy over a 600 cm^–1 tuning range were obtained.     

Tunable double-clad ytterbium-doped fiber laser based on a double-pass Mach-Zehnder interferometer

We have demonstrated an adjustable double-clad Yb³⁺-doped fiber laser using a double-pass Mach-Zehnder interferometer. The laser is adjustable over a range of 40 nm from 1064 nm to 1104 nm. By adjusting the state of the polarization controller, which is placed in the double-pass Mach-Zehnder interferometer, we obtained central lasing wavelengths that can be accurately tuned with controllable spacing between different tunable wavelengths. The laser has a side mode suppression ratio of 42 dB, the 3 dB spectral width is less than 0.2 nm, and the slope efficiencies at 1068 nm, 1082 nm and 1098 nm are 23%, 32% and 26%, respectively. In addition, we have experimentally observed tunable multi-wavelengths lasing output.     

A study of a Q-switched double-clad ytterbium-doped fiber laser with amplifying effect

A high repetition rate ytterbium-doped double-clad (YDDC) fiber laser with amplifying effect is described by using acousto-optic modulator. The characteristic of Q-switched pulses are studied with accurate control of opening gate time of modulator. The stable Q-switched pulses with tens of nanoseconds width can be observed at high repetition rate varied from 50 kHz to 500 kHz using this laser. The stable operation area of the Q-switched fiber laser is discussed and the analysis results agree well with that of the experiment.     

不同腔结构下的声光调Q双包层光纤激光器特性研究

报道了半导体激光器端面抽运不同结构的声光调Q的双包层光纤激光器的脉冲输出特性.对前向、后向不同抽运方式的掺镱调Q双包层光纤激光器在输出平均功率,调Q脉冲宽度及脉冲稳定性进行了对比及讨论;其中后向抽运的光纤激光器,在10 kHz重复频率调制下,获得了斜效率为60%的平均功率输出,其脉冲宽度为52ns,单脉冲能量为0.3mJ.最后利用不同抽运方式下的速率方程,理论分析调Q脉冲的特性,分析结果与实验相符.     

End-pumped, passively Q-switched Yb:YAG double-clad waveguide laser

We present a diode-pumped, double-clad Yb:YAG waveguide laser that contains an integrated section of a Cr(4+): YAG saturable absorber for passive Q switching. Using two 4-W polarization-coupled, broad-striped diode-pumped lasers, we obtained 30-microJ pulses of 1.6-ns duration at repetition rates of as much as 77 kHz. The slope efficiency was ~50% with respect to absorbed pump power, with a maximum output average power of 2.3 W and a peak power of ~18 kW . The output beam was single lobed, with M(2) values as great as 1.5x1.3 . We also demonstrate a passively Q -switched Nd:YAG waveguide laser of similar design, operating at 1.064 microm and 946 nm.     

Single-mode high-peak-power passively Q-switched diode-pumped Nd:YAG laser

We have demonstrated an efficient, compact, passively Q-switched single-mode diode-pumped Nd:YAG laser that uses Cr(4+):YAG as a saturable absorber. Linear- and ring-cavity configurations were demonstrated. Pulse energies and widths were, respectively, 1.5mJ and 3.9ns for the linear cavity and 2.1mJ and 12ns for the ring cavity.     

Linearly-polarized Tm-doped double-clad fiber laser

We report a linearly polarized Tm doped fiber laser. The fiber laser was set up by using a piece of polarization maintaining Tm doped double clad fiber of 5 m length as gain medium and a polarization beam splitter as a polarization selector. The fiber laser was pumped by a fiber pigtailed laser diode working at 790 nm with a maximum output power of 90 W. The linearly polarized Tm laser operated at wavelength around 2030 nm. A maximum output power up to 21.9 W was achieved when the pump power was 63.27 W with a threshold of 11.92 W, a slope efficiency of about 43.7%, and a polarization extinction ratio of 92.7% (11.37 dB). In addition to the blue fluorescence, we also observed the violet fluorescence under high pump power level. The up-conversion fluorescence was considered to be attributed to the ¹ G ₄ → ³ H ₆, and ¹ D ₂ → ³ F ₄ transitions of Tm ions, respectively.     

Tunable passively Q-switched ytterbium-doped fiber laser with mechanically exfoliated GaSe saturable absorber

A tunable passively Q-switched ytterbium-doped fiber laser using few-layer gallium selenide(GaSe) as a saturable absorber(SA) is demonstrated.The few-layer GaSe SA,which is fabricated by the mechanical exfoliation method,is able to generate a Q-switched fiber laser that has a maximum repetition rate of 92.6 kHz and a minimum pulsed width of 2.3 μs.The highest pulse energy exhibited by the generated pulse is 18.8 nJ with a signal to noise ratio of ~40 dB.The tunability of the proposed laser covers from 1042 to 1082 nm,giving a tuning range of 40 nm.     

50-watt ytterbium-doped double-clad fiber laser

A ytterbium-doped double-clad fiber laser with more than 50-W output, near diffraction-limited is demonstrated in SIOM. The optical-to-optical efficiency is about 44% with respect to incident pump power and the slope efficiency is 69% against launched pump power.     

Influence of stimulated Brillouin scattering on the temporal dynamics of an actively Q-switched double-clad fiber laser

The role of stimulated Brillouin scattering (SBS) during the active Q-switching of a typical high power double-clad fiber laser is experimentally and theoretically investigated. Our numerical model reproduces multiples Brillouin Stokes generation and the fast temporal dynamics which were experimentally observed. It clearly demonstrates that SBS is the cause of peak power enhancement effects such as giant pulse generation. The pulse formation process during the active Q-switching and the precise role of SBS in the pulse narrowing is detailed.     

Multi-coupler side-pumped Yb-doped double-clad fiber laser

The side-coupler of angle polished method, using angle-polished multimode fiber and optical adhesive, is used to efficiently pump an Yb-doped double-clad fiber laser. The maximum coupling efficiency of 78.6% is achieved by the side-coupler for a multimode fiber with a circular core of 200 μm and a double-clad fiber with a 350/400 μm D-shaped inner cladding. While laser diodes (LDs) with three side-couplers are simultaneously used as pump sources, maximum output power of 1.38 W and slope efficiency of 48.9% are demonstrated in the fiber laser system.     

High-energy, high-power ytterbium-doped Q-switched fiber laser

We report on a Q -switched, cladding-pumped, ytterbium-doped large-mode-area fiber laser operating at 1090 nm that is capable of generating 2.3 mJ of output pulse energy at a 500-Hz repetition rate and more than 5 W of average output power at higher repetition rates in a high-brightness beam (M(2) = 3) . Using a similar fiber with a smaller core, we generated >0.5-mJ pulses in a diffraction-limited beam. Our results represent a threefold increase in pulse energy over previously published values for Q-switched fiber lasers and firmly establish fiber lasers as compact, multiwatt, multimillijoule pulse sources with large scope for both industrial and scientific applications.     

90-fs stretched-pulse ytterbium-doped double-clad fiber laser

We report ultrashort, high-energy pulse generation from a side-pumped Yb-doped double-clad fiber laser. The laser is operating in the stretched-pulse regime. It directly generates 4.8-ps, 5-nJ pulses that are extracavity compressed to 90 fs.     

Short-pulse, high-peak-power Q-switched Tm–silica fibre laser at 1.9 m

High-performance Tm–silica fibre lasers operating at 1.9 μm when pumped at 1319 or 1064 nm have been Q-switched using a rotating mirror mounted at an asymmetric angle. Pumping by 1319 nm gives better performance compared with 1064 nm pumping due to greater excited state absorption (ESA) at 1064 nm. A short Q-switched pulse duration of 25 ns and a peak pulse power of about 2.7 kW has been obtained from a 1.8 m fibre for 3.5 W launched pump power at 1.3 μm. The Q-switch performance has been studied for variation of fibre length and shown that the optimum length under these pumping conditions is around 2 m.     

Numerical analysis and characterization of fiber Bragg grating-based Q-switched ytterbium-doped double-clad fiber lasers

A numerical model of the fiber Bragg grating (FBG)-based actively Q-switched double-clad fiber laser is presented in this paper. Based on numerical simulations, the influence of FBG on Q-switched pulse performance of Yb³⁺-doped double-clad fiber laser is studied, the pulse characteristics are discussed and analyzed using different FBG profiles, and further investigation is conducted to study the pulse characteristics of the fiber lasers under varying Q-switching conditions, including repetition rates, apodization profiles of FBG, peak reflectivity of the tunable FBG, cavity length and pump power.     

掺Yb3+双包层光纤激光器实验中的荧光分析

在研究掺Yb3+光纤激光器的实验中,发现伴生有可见区的荧光,用光谱仪测量发现该可见区荧光的波长分别为639.4 nm,520.7 nm,487 nm和474.8 nm,通过对比分析掺Yb3+光纤中杂质的能级结构,发现伴生的红、绿、蓝荧光由Yb3+与Pr3+合作产生,其荧光过程是由于Yb3+离子的能量转移给Pr3+,由Pr3+受激辐射产生的红、绿、蓝荧光.实验结果表明:掺Yb3+双包层光纤吸收泵浦光后产生的荧光是上转换的,这会导致光纤激光器激光能量转换效率的降低.     

All-fiber tunable ytterbium-doped double-clad fiber ring laser

We have designed and realized a cw all-fiber tunable Yb-doped double-clad fiber laser in a unidirectional ring cavity. The side-pumping V-groove technique is used, yielding very good launching efficiency of the high-power pumping laser diode, together with a compact configuration. The fiber laser delivers as much as 800 mW of power and is tunable in the spectral range 1.04-1.10 microm . The laser linewidth is ~0.1 nm .