全光纤激光器自启动锁模特性的理论研究

分析了带非线性放大光纤环的全光纤激光器的自启动锁模特性，得到了计算该激光器中光脉冲的有效能量增益的理论模型．结果表明，激光器的自启动锁模同掺Ｅｒ３＋光纤的增益及纤芯的有效截面积有关，并计算了自启动锁模的阈值峰值功率大小．应用本文的理论模型能成功地解释观察到的实验现象．     

有源耦合腔激光器锁模特性研究

本文在理论上首次发现有源耦合腔激光器的自启动锁模和时域调制特性,并对其进行了全面的分析和计算.对有源耦合腔激光器的自启动锁模机制和时域调制特性给予详尽的数值计算结果和清晰的物理图象解释,提出在有源耦合腔锁模激光器中可用连续泵浦源代替锁模泵浦源,而且有产生更短的光脉冲可能性.     

All-fiber wavelength tunable passively mode-locked erbium-doped ring laser

An all-fiber, wavelength-tunable, passively mode-locked erbium-doped ring laser is presented. Erbium-doped fibers (EDF) are used as the gain media because of their large gain bandwidth. Nonlinear polarization rotation (NPR) plays the dual role of realizing mode-locking and effectively adjusting the intensity-dependent loss of the cavity. An unbalanced Mach-Zehnder interferometer (UMZI) is used as a tunable optical beam filter. By using the UMZI and adjusting the polarization controllers (PCs), a sub-picosecond mode-locking laser is realized that is self-starting with central lasing wavelengths that can be accurately tuned over a range of about ~ \sim 30 nm and also has controllable spacings between different tunable wavelengths.     

利用啁啾脉冲光谱滤波和非线性偏振旋转技术实现高稳定性和开机自启动的全光纤掺Yb~(3+)光纤锁模激光器

建立理论模型,讨论了非线性偏振旋转全光纤锁模激光器的锁模过程、谐波过程以及导致激光器锁模运行难以稳定的影响因素.讨论了采用啁啾脉冲光谱滤波产生脉冲自振幅调制、增加激光器锁模稳定性和自启动能力的机理以及非线性偏振旋转与啁啾脉冲光谱滤波相结合实现锁模的物理过程和脉冲演化过程.研制出全光纤结构的超短脉冲掺Yb~(3+)光纤环形激光器,采用非线性偏振旋转和啁啾脉冲光谱滤波相结合的锁模技术,实现了激光器锁模的开机自启动和高稳定运行.对激光器进行了长期运行稳定性、锁模开机自启动能力、锁模输出参数可重复性监测.锁模脉冲中心波长1052.9 nm,谱宽9.1 nm,脉冲能量4.25 nJ,脉冲宽度17.8 ps.运行期间,各参数波动均小于0.3%.开机自启动能力和可重复性测试显示,激光器可实现一键自启动,启动后各参数可重复精度在0.55%以内.     

全光纤超短脉冲掺Yb3+光纤环形激光器

讨论了自启动被动锁模掺Yb³⁺光纤环形激光器产生短脉冲的机理，并研制出全光纤结构超短脉冲掺Yb³⁺光纤环形激光器.采用两个976nm半导体激光器级联抽运作为抽运源，高掺杂浓度掺Yb³⁺光纤作为增益介质，利用光纤的非线性偏振旋转效应，得到自启动、十分稳定的ps量级锁模光脉冲.激光器锁模阈值功率260mW，输出功率25mW，锁模光脉冲中心波长1056nm，3dB带宽11.7nm，重复频率20MHz.与其他结构光纤激光器相比，这种全光纤结构具有更高的效率和更好的稳定性. 关键词： 环形光纤激光器 3+光纤')" href="#">高掺杂浓度掺Yb³⁺光纤 自启动 被动锁模     

Theoretical and experimental studies on the self-Q-switched and mode-locked Nd:GdVO<Subscript>4</Subscript>/KTP green laser

A diode-pumped self-Q-switched and mode-locked intracavity frequency doubled Nd:GdVO₄/KTP green laser is presented. The self mode-locking is self-starting and stable. About 100% modulation depth for the self-mode-locked green pulses has been achieved. We propose a developed rate equation model for self-Q-switched and mode-locked lasers, using the hyperbolic secant function methods and the theory of Kerr-lens mode-locking. This will consider the cascading of second-order nonlinearities of KTP crystal, the third-order nonlinearity of the laser medium, influences of the continuous pump rate, and the stimulated radiation lifetime of the active medium. With the model developed, theoretical calculations are shown to be in good agreement with experimental results. The width of the mode-locked green pulse is estimated to be about 120 ps. PACS 42.60.Fc; 42.60.Gd; 42.65.Hw     

Passively mode-locked ytterbium fiber laser utilizing chirped-fiber-Bragg-gratings for dispersion control

A robust, self-starting picosecond pulse source based on ytterbium (Yb³⁺) doped fiber laser is described. Utilizing a chirped-fiber-Bragg-grating (C-FBG) for dispersion control, solitary mode-locking is obtained without bulk dispersion compensation elements. A semiconductor saturable absorber (SESAM) is used for stable self-starting. 3.6 ps pulses are produced, with 45 MHz basic repetition-rate and mW scale average output power at 1060 nm. Detailed numerical simulations based on the modified nonlinear Schrödinger equation agree well with the experimental results and are used as a design tool for the solitary mode-locked picosecond laser. The presented design can be simply employed in an all-fiber environmentally-stable system.     

利用光谱滤波器实现自启动的全光纤超短脉冲掺Yb3+光纤激光器

讨论了利用光谱滤波器实现自启动的被动锁模掺Yb³⁺光纤环形激光器的锁模机理,并研制出全光纤结构超短脉冲掺Yb³⁺光纤环形激光器.使用980 nm二极管激光器作为抽运源,高掺杂浓度掺Yb³⁺光纤作为增益介质.在净群速度色散为正的环形腔中加入光谱滤波器,抑制Yb³⁺离子在1030 nm强发射峰的同时,通过对啁啾脉冲的光谱滤波实现脉冲压缩.光谱滤波器与光纤非线性偏振旋转效应相结合,实现了激光器在1053 nm可自启动、十分稳定的锁模运转.激光器锁模阈值功率300 mW,平均斜率效率18.3%,最大输出功率53.07 mW,对应最大输出脉冲能量3.2 nJ.锁模光脉冲中心波长1053.6 nm,3 dB带宽10.84 nm,重复频率16.45 MHz.锁模脉冲宽度为皮秒量级,经腔外光栅对压缩至188 fs. 关键词： 3+光纤激光器')" href="#">掺Yb³⁺光纤激光器 自启动锁模 全光纤     

C. 超短激光光源

本文对超短激光脉冲的产生、压缩技术的最新发展做了详细评述。     

飞秒被动锁模环形腔掺Er3＋光纤激光器

在考虑增益、损耗、群速度色散、自相位调制、快速可饱和吸收体等各种参数同时作用情况下，分析了非线性偏振旋转效应自启动锁模机理，研究了腔体参数与锁模脉冲之间的关系，并给出飞秒被动锁模环形腔掺Er3＋光纤激光器实验原理。实验采用性能稳定的980nm半导体激光器作为抽运源，高掺杂短长度掺Er3＋光纤作为增益介质，利用非线性偏振旋转锁模技术，得到了稳定的飞秒自起振锁模光脉冲。抽运功率为23mW时，激光器输出锁模脉冲中心波长1552nm，3dB带宽为7.6nm，重复频率14.0MHz，平均输出功率0.43mW，自起振锁模泵浦阈值功率11.5mW,并观测到了稳定的高阶锁模脉冲输出。该激光器与报道过的相同结构光纤激光器相比,自起振泵浦阈值低、脉冲能量高、稳定性好，且频谱边带幅度小。     

自锁模掺钛宝石激光器的泵浦研究

对自锁模掺钛宝石激光器的原理作了较详细的描述，指出克尔透镜效应是形成自锁模的主要原因，但是，只有将克尔透镜自聚焦、振荡光参数和泵浦光参数三者结合起来考虑，才能全面了解自锁模的形成过程，本文从速率方程出发，得出了激光介质增益与光束参数的相对变化曲线，并据此来优化自锁模钛宝石激光器的设计，最后，将计算结果与实验作了比较，两者符合得较好。     

基于增益光纤长度优化的双波长运转掺铒光纤锁模激光器

构建了可自启动的双波长运转掺铒光纤锁模激光器.通过优化增益光纤长度,利用掺铒光纤在1530nm附近的再吸收效应调节激光器的增益谱,使激光器在1530nm和1560nm附近具有相同的增益强度.实验中采用31cm掺铒光纤作为增益光纤,以透射式半导体可饱和吸收体作为锁模器件,实现了自启动双波长锁模运转.激光器锁模输出重复频率为58.01MHz,信噪比为58.2dB,最高输出功率为4.8mW.锁模输出的光谱在1532.4nm和1552.3nm处具有两个强度接近的谱峰,谱峰间距约为20nm.该激光器无需手动调节即可实现双波长运转,更便于实际使用.     

Passively mode-locked fiber laser with kilohertz magnitude repetition rate and tunable pulse width

We propose and demonstrate a strictly all-fiber, erbium doped passively mode-locked figure-eight fiber laser (EDFL). In the laser structure, we use the nonlinear optical loop mirror combination with a variable ratio coupler (VRC-NOLM) to achieve mode-locking. Due to the nonlinear effect in the nonlinear fiber, stable self-starting pulse is obtained. In order to reduce the repetition of pulse, a segment of nonlinear fiber (NLF) has been incorporated into the VRC-NOLM. The laser generates stable rectangular pulses with a low repetition rate (kilohertz magnitude) by extending the length of the cavity. Furthermore, the output pulse width of the fiber laser can be varied by changing the coupler ratio of the variable ratio coupler.     

Mode-locked CW dye lasers

Mode-locking of CW dye lasers are described. Three different methods: active mode-locking by acoustic loss modulation, pumping with mode-locked pulses and passive mode-locking by a saturable absorber, all resulted in stable continuous trains of tunable mode-locked pulses of various duration. Best results were obtained using passive mode-locking by a saturable absorber. The pulse lengths for this case were measured by auto-correlation technique to be as short as 1.5 ps. Factors influencing the mode-locking and possible improvements are discussed.     

基于金属/介质混合反射镜的高调制深度半导体可饱和吸收镜锁模的飞秒光纤激光器

介绍了一种新型半导体可饱和吸收镜(SESAM)的原理与特性,并用它来实现掺铒光纤激光器的锁模飞秒脉冲的生成.这种新型宽带SESAM调制深度可以达到20%,用在1.5μm波段的环形腔掺铒光纤激光器里,实现自启动锁模.锁模光谱以1559 nm为中心,半峰全宽为9 nm,锁模激光脉冲串重复频率为25.6 MHz,输出功率14 mW,自相关仪测得脉宽为170 fs.     

Mechanism of pulse shaping in femtosecond lasers based on the high-order soliton

The mechanism of pulse shaping in Kerr-lens mode-locking Ti : sapphire lasers is investigated. Considering the balanced interaction between self-phase modulation, introduced by Kerr effect in Ti : sapphire, and group-velocity dispersion provided by prism-pair, pulse-splitting reflected in the intensity autocorrelation trace and pulse-compression display that the pulses outputting from different positions in laser cavity have different durations. We have concluded that the solitonlike pulse shaping that results from the competition between intracavity self-phase modulation within the Ti : S and negative group-velocity dispersion play dominant role in pulse evolution in Kerr-lens mode-locking lasers.     

Generation of 207-femtosecond pulses from a ytterbium figure-of-eight fibre laser

We report the generation of 207-fs pulses with 1.2mW average power at 1036nm directly from a passively mode-locked Yb-doped fibre laser with a nonlinear optical loop mirror for mode-locking and pairs of diffraction gratings for intracavity dispersion compensation. These results imply a 4-fold reduction in pulse duration over previously reported figure-of-eight cavity passively mode-locked Yb-doped fibre lasers. Stable pulse trains are produced at the fundamental repetition rate of the resonator, 24.0MHz. On the other hand, this laser offers a cleaner spectrum and greater stability and is completely self-starting.     

Self-starting simple structured dual-wavelength mode-locked erbium-doped fiber laser using a transmission-type semiconductor saturable absorber

A self-starting simple structured dual-wavelength passively mode-locked(ML) erbium-doped fiber(EDF) laser is proposed in this Letter. An all-fiber ring cavity is adopted and a transmission-type semiconductor saturable absorber is used as modelocker. In this laser, there are two gain humps located at the 1530 nm region and the 1550 nm region, respectively. Along with the length of EDF increasing, the intensity of the hump at 1530 nm region is gradually suppressed because of the re-absorption of emission by the ground state. With the proper length of EDF, the gain intensities of two regions are very close. When the pump power is above the ML threshold, the self-starting dual-wavelength ML operation is achieved easily without manual adjustment. The two spectral peaks with close intensities are located at 1532 and 1552 nm, respectively. The effect of intracavity dispersion on the output spectrum is also experimentally demonstrated.     

Passive synchronization of all-fiber lasers through a common saturable absorber

We present the synchronization of two all-fiber mode-locked lasers, operating at 1.0?μm and 1.54?μm, coupled through the use of a shared single-wall carbon nanotube absorber. Both lasers operate in the soliton-regime, achieving a synchronized repetition rate of 13.08?MHz. The broadband absorption range of the single-wall carbon nanotubes allows the stable mode-locking behavior at 1?μm and 1.5?μm. The nonlinear coupling effects between two energy states of the carbon nanotube absorber result in stable synchronized pulses for hours of operation, with a large cavity mismatch of 1400?μm.     

Characteristics of the loss modulation of intracavity Raman-Nath acousto-optic devices

Acousto-optic loss modulators for applications in active mode-locking of lasers are discussed. We show that intracavity interference effects can either enhance or decrease the modulation efficiency. Optical, electrical, and acoustic measurements for the characterization of mode-locking devices are described.