A compact graphene Q-switched erbium-doped fiber laser using optical circulator and tunable fiber Bragg grating

We demonstrate a passively Q-switched tunable erbium-doped fiber laser(EDFL)based on graphene as a saturable absorber(SA).A three-port optical circulator(OC)and a strain-induced tunable fiber Bragg grating(TFBG)are used as the two end mirrors in an all-fiber linear cavity.The Q-switched EDFL has a low pump threshold of 23.8 mW.The pulse repetition rate of the fiber laser can be widely changed from 9.3 kHz to 69.7 kHz by increasing the pump power from23.8 mW to 219.9 mW.The minimum pulse duration is 1.7μs and the highest pulse energy is 25.4 nJ.The emission wavelength of the laser can be tuned from 1560.43 nm to 1566.27 nm by changing the central wavelength of the straininduced TFBG.     

甲烷喇曼激光器研究

以甲烷作为喇曼散射物质,以YAG激光器输出的1.06μ激光作为泵浦光,研究甲烷喇曼激光器的某些特性。1.54μ激光输出能量约10毫焦,脉宽为6至10毫微秒。最佳总转换效率(电源输入能量到1.54μ激光输出能量),约为千分之一。     

Evolution of cat states in a dissipative parametric amplifier: decoherence and entanglement

The evolution of the Schr?dinger-cat states in a dissipative parametric amplifier is examined. The main tool in the analysis is the normally ordered characteristic function. Squeezing, photon-number distribution and reduced factorial moments are discussed for the single- and compound-mode cases. Also the single-mode Wigner function is demonstrated. In addition to the decoherence resulting from the interaction with the environment (damped case) there are two sources which can cause such decoherence in the system even if it is completely isolated: these are the decay of the pump and the relative phases of the initial cat states. Furthermore, for the damped case there are two regimes, which are underdamped and overdamped. In the first (second) regime the signal mode or the idler mode “collapses" to a statistical mixture (thermal field). Received 25 September 2001 / Received in final form 30 May 2002 Published online 13 December 2002 RID="a" ID="a"e-mail: sebaweh@awalnet.net.sa RID="b" ID="b"Joint Laboratory of Optics of Palacky University and Institute of Physics, Academy of Sciences of the Czech Republic, 17. listopadu 50, 772 07 Olomouc, Czech Republic.     

Short single-mode CO2 laser pulse generation by pulsed Q-switching

A simple method for the generation of short, single-mode CO₂ laser pulses produced by applying two voltage gates (of amplitude 3U_λ/4 and U_λ/4) to an electro-optic Q-switch placed in a three-mirror cavity is proposed. Single, single-mode, well-synchronizable pulses of 3 ns duration and of 3 mJ energy have been experimentally achieved from a TEA CO₂ laser with an intracavity Pockels cell with 3 ns switching time. Using a numerical simulation it is shown that with shorter switching time (≈1 ns) the method enables one to obtain, from such a laser, a single, megawatt pulse of 1 ns duration.     

LD Pumped Q-Switching and Self-starting Mode-locked All Fiber Laser

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被动调Q自拉曼Nd∶GdVO4激光器

对激光二极管(LD)抽运的自拉曼Nd∶GdVO4被动调Q激光器进行了详细的理论和实验研究。实验中采用Nd∶GdVO4晶体同时作为激光介质和拉曼晶体,分别用了两块不同初始透射率的Cr4 ∶YAG晶体,得到并比较了采用不同初始透射率的Cr4 ∶YAG晶体时被动调Q自拉曼激光器的性能。测量了平均输出功率、脉冲宽度和脉冲重复率随抽运功率的变化关系。当Cr4 ∶YAG的初始透射率为0.91,输入功率是5.7 W时,得到的拉曼光的最高功率为244.6 mW,相应的转换效率为4.3%。通过数值求解基频光和拉曼光空间分布的速率方程并应用到被动调Q自拉曼Nd∶GdVO4激光器。获得的理论结果与实验结果大致相符。     

Analytical and experimental studies on the diode-pumped,simultaneously Q-switched and mode-locked c-cut Nd:GdVO<Subscript> 4</Subscript>/KTP green laser with LT-GaAs absorber

A diode-pumped passively Q-switched mode-locked (QML) intracavity frequency doubled c-cut Nd:GdVO₄/KTP green laser with a LT-GaAs saturable absorber is presented. More than 90% modulation depth for the mode-locked green pulses has been achieved. Using the hyperbolic secant function methods, a developed rate equation model for Q-switched and mode-locked lasers considering the Gaussian spatial distribution of the intracavity photon intensity, the influences of continuous pump rate, the upper state lifetime of the active medium, and the excited-state lifetime of the saturable absorber, was proposed. With this developed model, the theoretical results are in good agreement with the experimental results and the width of the mode-locked green pulse was estimated to be about 380 ps.     

可调谐高重频高压脉冲驱动模块的设计

设计了一种高重频高压快脉冲驱动模块作用于激光调Q系统。该驱动模块采用零电压准谐振SMPS技术、大功率高速高压固体开关器件多管级联电路、大电流脉冲过驱动技术,获得了频率为1 kHz至100 kHz可调、高电平0~5 000 V可调、脉冲宽度0.5 μs、下降沿可达20 ns的负脉冲,可靠性强,体积小。     

Multi-Wavelength Q-Switched Ytterbium-Doped Fiber Laser with Multi-Walled Carbon Nanotubes

We demonstrate a passively multi-wavelength Q-switched Ytterbium-doped fiber laser (YDFL) based on a multi-wall carbon nanotubes embedded in polyethylene oxide film as saturable absorber. The YDFL generates a stable multi-wavelength with spacing of 1.9 nm as the 980 nm pump power is fixed within 62. 4 mW and 78.0 mW. The repetition rate of the laser is tunable from 10.41 to 29.04 kHz by increasing the pump power from the threshold power of 62.4 mW to 78 mW. At 78 mW pump power, the maximum pulse energy of 38 nJ and the shortest pulse width of 8.87 µs are obtained.