Ultralow-jitter passive timing stabilization of a mode-locked Er-doped fiber laser by injection of an optical pulse train

The pulse timing of a mode-locked Er-doped fiber laser was stabilized to a reference pulse train from a Cr:forsterite mode-locked laser by all-optical passive synchronization scheme. The reference pulses were injected into a ring cavity of the fiber laser by using a 1.3-1.5 mum wavelength-division multiplexer. The spectral shift induced by cross-phase modulation between copropagating two-color pulses realizes self-synchronization due to intracavity group-delay dispersion. The rms integration of timing jitter between the fiber laser pulse and the reference pulse was 3.7 fs in a Fourier frequency range from 1 Hz to 100 kHz.     

High-energy saturable absorber mode-locked fiber laser system

We demonstrate a mode-locked erbium-doped fiber laser with a 1-microm InGaAs saturable absorber that produces 84-ps, 1-nJ transform-limited pulses. Measurements of the InGaAs multiple quantum well revealed a slow saturable absorber that is useful for passive mode locking. Optical fiber was added to extend the cavity and vary the repetition rate from 51 kHz to 5.4 MHz. The narrow spectral width of the laser output (<0.04 nm) permits amplification to 0.2 microJ/pulse with minimal pulse broadening. Pulse energies as large as 1.7 microJ can be achieved with pulse widths of <330 ps. Average powers of 0.5 W at megahertz repetition rates are demonstrated.     

Synchronous Injection Locking Operation of Monolithic Diode Lasers Mode-Locked Diode Lasers

Synchronized mode-locking of monolithic mode-locked diode lasers has been demonstrated by injecting the light output from a master monolithic mode-locked diode laser. The master diode laser is a 10 GHZ hybridly mode-locked two section InGaASP quantum well laser. The slave lasers are a 10 GHz two section laser which is similar to the master laser, and a 20 GHz three section colliding pulse mode-locking laser. Both the slave lasers were greatly stabilized at 10 GHz frequency by a synchronous mode-locking mechanism under the injection of master laser pulses.     

Passive mode locking of lasers by crossed-polarization gain modulation

We report on a novel approach for inducing passive mode locking of lasers without using any saturable absorber but exploiting the polarization degree of freedom of light. In our scheme, passive mode locking is achieved by crossed-polarization gain modulation caused by the reinjection of a polarization-rotated replica of the laser output after a time delay. The reinjection time delay defines resonance tongues that correspond to mode-locking operation. Numerical continuation reveals that the cw solution is destabilized through a Hopf bifurcation that defines the onset of multimode operation which evolves sharply into a mode-locked solution. Our approach can be applied to a large variety of laser systems. For vertical-cavity surface-emitting lasers, we demonstrate stable mode-locked pulses at repetition rates in the GHz range and pulse widths of few tens of picoseconds.     

High energy giant chirped passively mode-locked Yb3+-doped fiber laser with nanoseconds to picoseconds pulses

We report an all normal dispersion low repetition rate high energy passive mode-locked ytterbium-doped fiber laser with output pulses duration ranging from nanoseconds to picoseconds. The mode-locking mechanism of the laser is based on nonlinear polarization evolution and strong pulses shaping with a cascade long-period fiber grating bandpass filtering in highly chirped pulses. The laser generates highly stable pulses duration from 2.62 ns to 315 ps with a maximum pulse energy of 49.5 nJ and 2.5435 MHz repetition rate.     

Different operation states of soliton pulses in an erbium-doped fibre ring laser

We report on the experimental observation of soliton pulses in an erbium doped fibre ring laser. The passive mode-locking is achieved using the nonlinear polarization rotation technique. By adjusting the pump power and the intracavity polarization controllers, a normal soliton, a stable 8th harmonic mode-locked pulse and a noise-like pulse have been observed in our laser. The experimental results revealed that the noise-like pulse is not suitable for the optical telecommunication, and in order to obtain the stable harmonic mode-locked soliton, a strong unstable CW laser field is necessary to mediate global soliton interaction. The formation mechanism of the harmonic mode-locked pulse has also been analysed.     

Switchable different operation states in an erbium-doped fiber laser cavity with normal dispersion

We demonstrate different operation states which can be switched by the polarization control in an erbium-doped fiber laser cavity with normal dispersion, including passive single-pulse and multiple-pulse mode-locking, coherent pulse pattern, and passive Q-switching. The mode-locked single pulse has a smooth and broad rectangular-shaped spectrum. With increasing pump power, multiple pulses appear and finally six pulses are observed, where the pulses have no interaction with each other. Keeping the pump power at 407 mW and adjusting the polarization state, we observe the coherent pulse pattern with the pulse numbers from 2 to 5. It is the first time five coherent pulses in the 1.55 μm normal dispersion cavity have been observed, to our knowledge. The mode-locked spectra are highly modulated and the largest pulse separation of 31.9 ps is observed for the two-pulse case. When the pump power exceeds 180 mW, the mode-locked operation can be switched to the passively Q-switched operation by controlling the polarization state. The repetition rate and pulse width can be changed by pump power variation, and the spectrum is tunable in the range of 8.45 nm.     

Cavity-enhanced similariton Yb-fiber laser frequency comb: 3 x 10(14) W/cm2 peak intensity at 136 MHz

We report on a passive cavity-enhanced Yb-fiber laser frequency comb generating 230 MW of peak power (3 kW of average power) at a 136 MHz pulse repetition rate. The intracativy peak intensity of 3 x 10(14) W/cm2 for the 95 fs pulse is sufficient to ionize noble gases, such as Xe, Kr, or Ar. The laser system is based on a mode-locked Yb-fiber similariton oscillator in conjunction with a cladding-pumped chirped-pulse fiber amplifier. After recompression, 75 fs duration pulses at a 13.1 W average power are obtained. These pulses are then coherently added inside a passive ring cavity by controlling the fiber oscillator's pulse repetition rate and carrier-envelope offset frequency. This system is well suited for studying high-field phenomena at very high pulse repetition rates.     

石墨烯被动锁模全正色散掺镱光纤激光器中的暗脉冲及其谐波

报道了一种基于石墨烯被动锁模的全正色散掺镱环形光纤激光器. 在激光器腔中应用激光诱导沉积法制备的石墨烯可饱和吸收体, 通过调节抽运光功率和偏振控制器的角度分别得到了明脉冲及其二阶谐波, 暗明脉冲对和暗脉冲及其二、三阶谐波这三类不同的脉冲. 其中, 暗明脉冲对和暗脉冲在基于石墨烯被动锁模的掺镱光纤激光器实验中都是第一次被观察到. 本文根据实验结果结合模拟分析了暗脉冲的产生机理, 并研究对比了明脉冲谐波和暗脉冲谐波产生的原因.     

Unidirectional travelling wave operation of a mode-locking Nd:Glass ring laser

The development of unidirectional mode-locked pulses in a Nd:glass ring laser is studied for various combinations of active and passive mode-locking and pulse direction discrimination elements.     

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。     

Diode-pumped passively mode-locked Nd:CaNb<Subscript>2</Subscript>O<Subscript>6</Subscript> laser

We have experimentally demonstrated a diode-pumped passively mode-locked Nd:CaNb₂O₆ laser for the first time to our best knowledge. With a semiconductor saturable absorber mirror (SESAM) as a passive mode locker, the laser generated stable mode-locked pulses with pulse duration of 17.3 ps and repetition rate of 88.4 MHz. With a singe-emitter laser diode pumping, the maximum average output power of the mode-locked laser was 0.843 W, with a slope efficiency of 23%. The experimental results show the Nd:CaNb₂O₆ crystal is a promising laser gain medium for picosecond pulse generation.     

Pulse characterisation of a quantum-well mode-locked laser diode by two-photon absorption frequency-resolved optical gating

The intensity and phase of ultrashort optical pulses from a 40-GHz monolithic InGaAsP quantum-well heterostructure laser diode are retrieved for the first time from two-photon absorption pulse spectrograms. The pulse traces showing the mode-locked pulses from the laser are distorted due to ultrafast absorption saturation associated with quantum-confined Stark excitons. It is suggested from comparison between experimental time-integrated spectrum and reconstructed pulse spectrum that the mode-locked pulses are formed only from a part of the longitudinal modes in the laser cavity.     

High-power passively mode-locked tapered InAs/GaAs quantum-dot lasers

We report picosecond pulse generation with high peak power in the range of 3.6 W from monolithic passively mode-locked tapered quantum-dot laser diodes, exhibiting low divergence and good beam quality. These results were achieved using a gain-guided tapered laser geometry. The generation of picosecond pulses with high average power up to 209 mW directly from such tapered lasers is also demonstrated, corresponding to 14.2 pJ pulse energy (14.65 GHz repetition rate). A comparison between the mode-locking performance of these tapered lasers incorporating either five or ten layers of InAs/GaAs self-organized quantum dots in their active layer is also presented.     

Wavelength-tunable prism-coupled external cavity passively mode-locked quantum-dot laser

A wavelength-tunable mode-locked quantum dot laser using an In As/Ga As quantum-dot gain medium and a discrete semiconductor saturable absorber mirror is demonstrated.A dispersion prism,which has lower optical loss and less spectral narrowing than a blazed grating,is used for wavelength selection and tuning.A wavelength tuning range of 45.5 nm(from1137.3 nm to 1182.8 nm) under 140-m A injection current in the passive mode-locked regime is achieved.The maximum average power of 19 m W is obtained at the 1170.3-nm wavelength,corresponding to the single pulse energy of 36.5 p J.     

8字形腔波长可调谐锁模脉冲光纤激光器

采用非线性光纤环形镜加脉冲锁模技术及可调谐光纤光栅滤波器,对8字形腔被动锁模掺铒光纤激光器进行了波长可调谐输出的实验研究.在EDFA抽运光功率一定的情况下,通过调节偏振控制器和可调谐光纤光栅滤波器,获得了光谱稳定、重复频率1.1 MHz、输出功率起伏小于0.8 dBm、中心波长在1 548~1 570 nm内连续可调的短脉冲输出.该激光器可实现自启动锁模,且长时间稳定工作无需任何调整.     

Analysis of a laser-diode end-pumped intracavity frequency-doubled passively Q-switched and mode-locked Nd:GdVO<Subscript>4</Subscript>/KTP laser with a semiconductor saturable absorber

A diode-pumped passively Q-switched mode-locked (QML) intracavity frequency-doubled Nd:GdVO₄/KTP green laser with a semiconductor saturable absorber is presented. Nearly 100% modulation depth for the mode-locked green pulses can be achieved at any pump power over 1.92 W. The width of the mode-locked green pulse was estimated to be about 150 ps. The mode-locked pulse interval within the Q-switched envelope of 320 ns and the repetition rate of 97.5 kHz were obtained, at an incident pump power of 4.4 W. The repetition rate of the mode-locked green pulses inside the Q-switched envelope was 140 MHz.     

被动谐波锁模掺Yb3+光纤环形激光器

 利用光纤的非线性偏振旋转效应产生可饱和吸收体的锁模机制，从掺Yb³⁺光纤环形激光器中得到稳定高阶谐波锁模光脉冲。理论分析了工作于正色散区的掺Yb³⁺光纤环形激光器的特性。实验中观测到了掺Yb³⁺光纤环形激光器3种不同演化方式产生高阶锁模光脉冲。4阶谐波锁模脉冲（107.2 MHz重复频率）经过1 m长高掺杂Yb³⁺光纤放大器放大后产生了平均功率100 mW，脉宽22.8 ps的脉冲，最后经过光栅压缩得到了平均输出功率20 mW，脉宽307 fs，脉冲中心波长1 051.2 nm，带宽13.76 nm的激光。     

Negative feedback using a nonlinear mirror for the generation of a long train of short light pulses

A nonlinear mirror is used to provide a passive negative feedback in an actively mode-locked pulsed Nd:YAG laser. Trains of 250 ps pulses with a total length of up to 50 microseconds were generated. The train duration is limited only by the flashlamp pump pulse length.On leave from Department of Physics, University of Sofia, BG-1126 Sofia, Bulgaria     

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