Passively Q-Switched Yb:YAG Laser with Cr(4+):YAG as the Saturable Absorber

By using a continuous-wave Ti:sapphire laser as a pumping source, we demonstrated a passively Q-switched Yb:YAG laser at room temperature with Cr(4+):YAG as the saturable absorber. We achieved an average output power of as much as 55 mW at 1.03 mum with a pulse width (FWHM) as short as 350 ns. The initial transmission of the Cr(4+):YAG has an effect on the pulse duration (FWHM) and the repetition rate of the Yb:YAG passively Q-switched laser. The Yb:YAG crystal can be a most promising passively Q-switched laser crystal for compact, efficient, solid-state lasers.     

High-repetition rate Q-switched Nd:YVO4 laser with a composite semiconductor absorber

A diode-pumped Nd:YVO4 laser passively Q switched by a semiconductor absorber is demonstrated. The Q-switched operation of the laser has an average output power of 135 mW with a 1.6 W incident pump power. The minimum pulse width is measured to be about 8.3 ns with a repetition rate of 2 MHz. To our knowledge, this is the first demonstration of a solid-state laser passively Q-switched by such a composite semiconductor absorber.     

Laser-diode-pumped passively Q-switched Nd:YVO4 green laser with periodically poled KTP and GaAs saturable absorber

A laser-diode-pumped passively Q-switched Nd:YVO₄ green laser with periodically poled KTP (PPKTP) and GaAs saturable absorber has been realized. The dependences of pulse repetition rate, pulse energy, pulse width and peak power on incident pump power for the generated-green-light pulses are measured. At the maximum incident pump power of 4.1 W, the maximum average output power of 113 mW is obtained, corresponding to an optical conversion efficiency of 2.8%. At the same pump power, stable green laser pulses of duration of 44.6 ns and energy of 0.28 µJ are generated at a repetition rate of 403.4 kHz. The coupling wave rate equations for a passively Q-switched laser are also given and the numerical solutions agree with the experimental results.     

Enhancement of stability and peak power in a diode-pumped doubly QML YVO4/Nd:YVO4 laser with EO and Cr:YAG saturable absorber

A diode-pumped doubly Q-switched and mode-locked (QML) YVO₄/NdYVO₄ laser is realized with the electro-optic (EO) modulator and Cr⁴⁺:YAG saturable absorber, in which the repetition rate of the Q-switched envelope is controlled by the active EO modulation while the mode-locked pulses inside the Q-switched envelope depend on both the actively modulated loss and the passive saturable absorption. The experimental results show that the doubly QML laser can generate more stable and shorter pulses with higher peak power when compared with the singly passively QML laser with Cr⁴⁺:YAG. At the pump power of 20 W and the repetition rate 1 kHz, a 21 ns Q-switched pulse envelope with a average mode-locked peak power of 544 kW is obtained, which is the shortest Q-switched pulse envelope to my knowledge. In comparison to the singly passively QML laser with Cr⁴⁺:YAG, the doubly QML laser has compressed the Q-switched envelope pulse width 70% and improved the mode-locked pulsed peak power 27 times. By using a hyperbolic secant square function and considering the Gaussian distribution of the intracavity photon density, the coupled equations for diode-pumped dual-loss-modulated QML laser is given and the numerical solutions of the equations are in good agreement with the experimental results.     

Tunable passively Q-switched thulium doped fluoride fibre (TDFF) laser using reduced graphene oxide-silver (rGO-Ag) as saturable absorber

A tunable, passively Q-switched thulium doped fluoride fibre (TDFF) laser using a reduced-graphene oxide-silver (rGO-Ag) thin film as a saturable absorber (SA) for S band operation is proposed and its efficacy demonstrated. Over a pump power range of 91.4?mW up to 158.6?mW, passively generated Q-switched pulses are observed with repetition rates from 20 to 34.5?kHz and pulse widths from 3.1 to 7.1?µs. The highest pulse energy observed is 101.2?nJ with a signal to noise ratio of ～42?dB. The proposed laser has a tuning range ～52?nm from 1458 to 1510?nm with a tunable bandpass filter (TBPF) introduced into the cavity.     

Efficient quasi-continuous-wave and passively Q-switched laser operation of a Nd3+:BaGd2(MoO4)4 cleavage plate

Pumped by a Ti:sapphire laser at 807 nm, efficient quasi-cw and passively Q-switched laser operations have been realized from a 1.1 mm thick, 1.2 at. % Nd(3+):BaGd(2)(MoO(4))(4) cleavage plate in a plano-plano cavity. When the absorbed pump power was 1060 mW, the achieved maximum quasi-cw output power was 580 mW. The slope efficiency and absorbed pump threshold power were 60% and 50 mW, respectively. Using a Cr(4+):YAG crystal with an initial transmission of 85% as the saturable absorber, a pulse laser with 3.0 microJ energy, 30 ns duration, and 52 kHz repetition rate has been obtained when the absorbed pump power was 1060 mW. The polarization characteristic and laser spectra of both the quasi-cw and passively Q-switched lasers have been measured.     

Wide-band,passively Q-switched Yb- and Tm-doped fibre laser using WSSe saturable absorber

A wide-band, passively Q-switched fibre lasers based on ytterbium- and thulium-doped fibre gain medium are proposed and demonstrated. The lasers employ a transition metal dichalcogenide, tungsten sulphoselenide as a saturable absorber (SA) which is prepared by mechanical exfoliation technique. By integrating the SA in the laser cavities, self-starting Q-switched at 1038 and 1982?nm are obtained. The generated pulses exhibit a microsecond pulse duration with few kilohertz repetition rate. The proposed SA has high potential as a new material to cater to the needs of various scientific, industrial and biomedical applications.     

Cr~(4+):YAG被动调Q Nd:YAG陶瓷激光器输出特性研究

本文对Cr~(4+):YAG被动调Q Nd:YAG陶瓷激光器的输出特性进行了理论和实验研究.在相同泵浦功率和不同输出耦合透过率条件下,实验测量了被动调Q陶瓷激光器的输出激光重复频率、平均输出功率以及单脉冲能量,并与理论计算结果进行了比较.研究结果表明,随着输出耦合透过率的增加,输出激光重复频率单调减小,而平均输出功率及单脉冲能量则呈现出先增加后减小的变化趋势,只是平均输出功率及单脉冲能量所对应的最佳输出耦合透过率会有所不同.     

Semiconductor saturable absorber mirror passively Q-switched fiber laser near 2 μm

A passively Q-switched fiber laser near 2?μm is achieved with a semiconductor saturable absorber mirror (SESAM) as a saturable absorber. Stable Q-switched pulses are generated from an extremely compact setup with a central wavelength of 1958.2?nm. Under the bidirectional pump configuration, the repetition rate of the fiber laser can be widely tuned from 20 to 80?kHz by increasing the pump power at the same time the pulse width decreases from 1?μs to 490?ns. When the incident pump power is 1.3?W, the average output power, the pulse repetition rate, the pulse width, and the highest single pulse energy are 91?mW, 80?kHz, 490?ns, and 1.14?μJ, respectively. To further optimize the system configuration, the pulse width can be reduced to 362?ns when the cavity length is reduced.     

Passively Q-switched Nd:YVO4 waveguide laser using graphene as a saturable absorber

We report on passively Q-switched lasers in femtosecond laser written waveguide in Nd:YVO₄ crystal. Using graphene as a saturable absorber, passively Q-switched waveguide laser operations are achieved along both TE and TM polarizations with single modal profiles. Furthermore, all-angle linear light pump was utilized to investigate the thorough information of the polarization effects of the laser, showing that the optimum polarization for laser generation is TE. The maximum average output power is estimated to be 129 mW with 12.2% slope efficiency, corresponding to single-pulse energy of 8.1 nJ, pulse duration of 25.0 ns and repetition rate of 16.3 MHz.     

Triple-wavelength passively Q-switched ytterbium-doped fibre laser using zinc oxide nanoparticles film as a saturable absorber

We report on the generation of a triple-wavelength passively Q-switched ytterbium-doped fibre laser using a saturable absorber (SA) based on zinc oxide nanoparticles (ZnO NPs) film. The SA was fabricated by embedding ZnO NPs powder into a polyvinyl alcohol as a host polymer. By properly adjusting the pump power and the polarization state, single-, dual- and triple-wavelength Q-switching are stably generated without additional components (such as optical filter, or fibre grating). For the triple wavelength operation, the fibre laser generates a maximum pulse repetition of 87.9 kHz with the shortest pulse duration of 2.7 μs. To the best of authors’ knowledge, it’s the first demonstration of triple-wavelength passively Q-switching fibre laser using ZnO NPs as a SA. Our results suggest that ZnO is a promising SA for multi-wavelength laser operation.     

Laser-diode pumped passively Q-switched Nd3+:NaY(WO4)2 laser with Cr4+:YAG saturable absorber

A laser-diode pumped passively Q-switched new type crystal Nd³⁺:NaY(WO₄)₂ (known as Nd:NYW) laser with Cr⁴⁺:YAG saturable absorber has been realized. The dependence of pulse repetition rate, pulse energy, pulse width, and peak power on pump power for different small-signal transmission of Cr⁴⁺:YAG are measured. The coupled rate equations are used to simulate the Q-switched process of laser, and the numerical solutions agree with the experimental results.     

Polarization-resolved study of diode-pumped passively Q-switched Nd:GdVO4 lasers

By using the natural birefringence of an a-cut Nd:GdVO(4) crystal, we experimentally investigate laser operation under different light polarizations (pi- and sigma-polarized emissions) and compare their performance. The laser performance is further compared with a diode-pumped c-cut Nd:GdVO(4) laser of the same parameters. We show experimentally that the c-cut Nd:GdVO(4) laser could have good passively Q-switched performance in a low-pump-power region but is influenced by other intrinsic laser effects, such as the thermally induced cavity losses; its performance is severely degraded under high pump power. The best passively Q-switched performance obtained in our experiments is from the a-cut pi-polarized laser, which gives the narrowest pulse of 5.4 ns with the highest peak power of 20 kW. Our experimental results show that, to achieve the best performance of the passively Q-switched laser operation, an overall consideration of laser parameters is important.     

Passively Q-switched fibre laser utilizing erbium-doped fibre saturable absorber for operation in C-band region

In this paper, a stable and robust all-fibre passively Q-switched erbium-doped fibre laser (EDFL) emitting at 1558?nm is described. The proposed laser utilizes an 11?cm long erbium-doped fibre as saturable absorber (SA). The fibre SA features a linear optical absorption of about 13?dB in the Q-switched EDFL operating regime. By elevating the input pump power from the threshold of 60?mW to the maximum available power of 142?mW, a pulse train with a maximum repetition rate of 86?kHz, minimum pulse width of 3.39?µs, maximum average output power of 10.5?mW, maximum pulse energy of 122?nJ and maximum peak power of 36?mW are obtained. The signal to noise ratio (SNR) of the spectrum is measured to be around 70?dB. This fibre SA is simple, reliable, compact and alignment free. Thus it is suitable for making a portable pulse laser source.     

激光引信用微宝石激光器设计

针对微宝石激光器在激光引信领域的应用需求,从激光二极管泵浦Cr4 :YAG被动调Q微宝石激光器速率方程出发分析了输出镜反射率、Cr4 :YAG晶体初始透过率、泵浦速率对激光器输出参量的影响及其变化规律.理论计算表明,文中设计的激光器理论上可以实现短脉冲(＜1.5ns)、高峰值功率(14.5kW)、高重频(泵浦光为1W情况下激光重复频率为7.2kHz)的稳定激光输出.最后给出了Cr4 :YAG晶体运转过程,并以此为基础分析了微宝石激光器的稳定性.计算分析表明,微宝石激光器理论上可以满足激光引信用激光器的要求.     

Passively Q-switched 1.57-microm intracavity optical parametric oscillator

We demonstrate an eye-safe KTP-based optical parametric oscillator (OPO) driven intracavity by a diode-pumped 1064-nm Nd:YAG laser, passively Q-switched by a Cr4+:YAG crystal. The characteristics of this system, which operates at 1570 nm with a repetition rate as high as 50 Hz, are studied as a function of Cr4+:YAG optical density. Under optimum conditions the OPO generates 1.5-mJ, 3.4 +/- 0.1-ns pulses in a single transverse mode. For a Cr4+:YAG Q-switch element with an optical density of 0.5 the conversion efficiency of the intracavity energy is approximately 45% with the ratio of OPO to Nd:YAG peak-pulse intensity exceeding unity. These and other OPO characteristics compare favorably with a simple rate equation model of the OPO dynamics.     

Q-switched 2-micron lasers by use of a Cr2+:ZnSe saturable absorber

Flash-lamp-pumped Ho:YAG (2090-nm) and Tm:YAG (2017-nm) lasers were, for the first time to our knowledge, passively Q switched by use of a Cr(2+):ZnSe saturable absorber. A Q-switched Ho laser with 1.3-mJ pulse energy and ~90-ns pulse duration and a Q-switched Tm laser with ~3.2-mJ pulse energy and 90-ns pulse duration were demonstrated. Compared with the free-running output energies at the Q-switching threshold pump levels, the Q-switching efficiencies were approximately 5% for the Ho:YAG laser and 16% for the Tm:YAG laser.     

Watt-level Q-switched Nd:LuVO4 laser based on a graphene oxide saturable absorber

The demonstration is reported of a diode-pumped passively Q-switched Nd:LuVO₄ laser at 1064 nm using a transmission-type graphene oxide as the saturable absorber. The graphene oxide saturable absorber with a modulation depth of 10% was fabricated using a vertical evaporation method. With a pump of 11.5 W, a maximum output power of 1.353 W was obtained with 186-ns pulse duration and 336.7-kHz repetition rate, corresponding to a maximum pulse energy of 4 μJ per pulse.     

Optimization of the pulse-width of diode-pumped passively Q-switched mode-locked c-cut Nd:GdVO4 laser with a GaAs saturable absorber

By considering the single-photon absorption and two-photon absorption processes in the GaAs saturable absorber, the coupled rate equations for a diode-pumped passively Q-switched and mode-locked (QML) laser with GaAs coupler under Gaussian approximation are given. These rate equations are solved numerically. The key parameters of an optimally coupled passively QML laser with the shortest pulse-width envelope are determined. These key parameters include the parameters of the gain medium, the saturable absorber, and the resonator, which can minimize the pulse-width of a singly Q-switched envelope. Sample calculations for a diode-pumped passively Q-switched mode-locked c-cut Nd:GdVO(4) laser with a GaAs coupler are presented to demonstrate that the shortest pulse-width envelope can be obtained by selecting the optimal small-signal transmission of the saturable absorber and the reflectivity of the output mirror.     

Compact Q-switched and mode-locked Nd³⁺:YVO₄/Cr⁴⁺:YAG self-Raman laser

Compact passively Q-switched and mode-locked Nd³⁺:YVO₄/Cr⁴⁺:YAG self-Raman laser with high mode-locked repetition rate was demonstrated. The picosecond first Stokes at 1176?nm was successfully obtained. At the maximum incident pump power, the average output power was 95?mW with the mode-locked pulse repetition rate of 940?MHz. Yellow laser output of 588.2?nm was also realized by the use of LiB₃O₅ frequency doubling crystal.