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.     

Characteristics of wave-breaking-free operation in a passively mode-locked all-fiber ring laser based on AS-Yb-PBGF

A passively mode-locked all-fiber ring laser is constructed based on all-solid Yb-doped photonic bandgap fibers (AS-Yb-PBGF), which provides the laser gain and anomalous dispersion simultaneously. Without any other dispersion compensators, the cavity is simple, compact, and maintenance- and alignment-free. The characteristics of wave-breaking-free operation in the laser are investigated by means of numerical simulations using the split-step Fourier method. The approximately parabolic pulses can be generated and evolved for maintaining the normal group-velocity dispersion intracavity, when the length of the single-mode fiber is between 2 and 4 m. The obtained highest energy of the output pulse is up to 2.27 nJ with the pulse duration of 8.61 ps, corresponding to the time-bandwidth product of 10.05. By dechirping out of cavity, the pulse duration is 0.70 ps.     

Switchable and tunable dual-wavelength ultrashort pulse generation in a passively mode-locked erbium-doped fiber ring laser

A simple switchable and tunable dual-wavelength passively mode-locked erbium-doped fiber ring laser based on nonlinear polarization rotation (NPR) effect is proposed and experimentally demonstrated. The NPR effect effectively induces wavelength- and intensity-dependent loss to readily implement stable dual-wavelength passively mode-locked operation. The wavelength switching and tuning of the dual-wavelength ultrashort pulse laser are achieved only by appropriately rotating the polarization controllers. The side-mode suppression ratio of the output pulse is larger than 41 dB over a wavelength-tuning range of 43.4 nm. Moreover, triple-wavelength ultrashort pulse can also be observed.     

120 nm Bandwidth noise-like pulse generation in an erbium-doped fiber laser

We report on the generation of noise-like pulses with up to 120 nm bandwidth in a passively mode-locked erbium-doped fiber ring laser. By inserting a segment of slightly normal dispersion fiber in a mode-locked fiber laser cavity, we found that the spectrum of the noise-like pulse emission of the laser can be significantly broadened as a result of the four-wave-mixing and the soliton self-frequency shift effects in the inserted fiber.     

Tunable and switchable dual-wavelength passively mode-locked fiber ring laser with high-energy pulses at a sub-100 kHz repetition rate

We demonstrate a tunable and switchable dual-wavelength passively mode-locked fiber ring laser in the anomalous dispersion regime that generates high-energy pulses at a sub-100 kHz repetition rate. The nonlinear polarization rotation (NPR) technique is employed in this configuration to allow for passively mode-locked operation. By exploiting the intensity-dependent loss caused by NPR, the mode competition could be efficiently alleviated. Moreover, taking advantage of the intrinsic spectral filter induced by the intracavity birefringence, the dual-wavelength separations as well as the wavelength lasing locations could be flexibly tuned by properly rotating the polarization controller. With a repetition rate of 85.8 kHz, the laser delivers the single pulse energy of 198 nJ at a pump power of 250 mW. The combination of high per-pulse energy and flexible tunability in this fiber laser is useful for practical applications.     

Passive mode-locking of the Yb:CNGG laser

Passive mode-locking using a SESAM is demonstrated for the Yb-doped cubic non-stoichiometric crystal CNGG which exhibits local disorder. The pulse duration of 73 fs obtained is the shortest for an isotropic Yb-doped laser crystal while larger output coupling resulted in average output powers of 750 mW with 66% efficiency in the mode-locked regime.     

Millijoule pulse energy picosecond fiber chirped-pulse amplification system

The efficient generation of a 1.17-mJ laser pulse with 360 ps duration using an ytterbium (Yb)-doped fiber amplifier chain seeded by a homemade mode-locked fiber laser is demonstrated experimentally.A specially designed figure-of-eight fiber laser acts as the seed source of a chirped-pulse amplification (CPA) system and generates mode-locked pulses with hundreds of picosecond widths.Two kinds of large-mode-area (LMA) double-clad Yb-doped fibers are employed to construct the pre-amplifier and main amplifier.All of the adopted instruments help avoid severe nonlinearity in fibers to raise sub-nanosecond pulse energy with acceptable signal-to-noise ratio (SNR).The output spectrum of this fiber-based CPA system shows that amplified spontaneous emission (ASE) is suppressed to better than 30 dB,and the onset of stimulated Raman scattering is excluded.     

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.     

Raman-Assisted Passively Mode-Locked Fiber Laser

We propose and demonstrate a Raman-assisted passively mode-locked Yb-doped fiber laser in a normal dispersion regime. A section of highly nonlinear fiber is adopted to enhance the nonlinearity to extend the bandwidth of the gain spectrum by the stimulated Raman effect. The mode-locked fiber laser emits a broad spectral bandwidth of 64 nm at the-20 dB level and a highly stable pulse operation with a signal-to-noise ratio of 77 dB.     

Yb-doped passively mode-locked fiber laser with Bi_2Te_3-deposited

In this study we present an all-normal-dispersion Yb-doped fiber laser passively mode-locked with topological insulator(Bi2Te3) saturable absorber. The saturable absorber device is fabricated by depositing Bi2Te3 on a tapered fiber through using pulsed laser deposition(PLD) technology, which can give rise to less non-saturable losses than most of the solution processing methods. Owing to the long interaction length, Bi2Te3 is not exposed to high optical power, which allows the saturable absorber device to work in a high power regime. The modulation depth of this kind of saturable absorber is measured to be 10%. By combining the saturable absorber device with Yb-doped fiber laser, a mode-locked pulse operating at a repetition rate of 19.8 MHz is achieved. The 3-d B spectral width and pulse duration are measured to be 1.245 nm and317 ps, respectively.     

Femtosecond mode-locked Yb fiber laser for single-mode fiber chirped pulse amplification system

High-peak-power laser systems are based on the chirped pulse amplification (CPA) technique. CPA laser system needs a mode-locked laser oscillator for stable ultrashort pulse laser generation. We report a single-mode fiber CPA system which consists of stable mode-locked Yb-doped fiber laser oscillator with a wide tuning range, chirped fiber Bragg grating stretcher, and two Yb-doped fiber amplifiers. The single-mode fibers can generate high-quality and single-mode beams which are stable for long time.     

SOA-based actively mode-locked fiber ring laser by forward injecting an external pulse train

An actively mode-locked fiber ring laser based on cross-gain modulation (XGM) in a semiconductor optical amplifier (SOA) is demonstrated to operate stably with a simple configuration. By forward injecting an easily-generated external pulse train, the mode-locked fiber laser can generate an optical-pulse sequence with pulsewidth about 6 ps and average output power about 7.9 mW. The output pulses show an ultra-low RMS jitter about 70.7 fs measured by a RF spectrum analyzer. The use of the proposed forward-injection configuration can realize the repetition-rate tunability from 1 to 15 GHz for the generated optical-pulse sequences. By employing a wavelength-tunable optical band-pass filter in the laser cavity, the operation wavelength of the designed SOA-based actively mode-locked fiber laser can be tuned continuously in a wide span between 1528 and 1565 nm. The parameters of external-injection optical pulses are studied experimentally to optimize the mode-locked fiber laser.     

Pulse shortening and quality improvement based on spectral filtering in a stretched-pulse mode-locked fiber laser with large third-order dispersion

We demonstrate a passively mode-locked ring fiber laser operating in the stretched-pulse regime. The ring cavity model is constructed with standard single-mode fiber and dispersion delay line for dispersion management. Here, all-solid Yb-doped photonic bandgap fiber is used as the dispersion delay line and provides laser gain simultaneously. As the all-solid Yb-doped photonic bandgap fiber has large third-order dispersion, it is necessary to study its impact on the stretched-pulse operation. The presence of the third-order dispersion reduces pulse quality because of the relatively small group velocity dispersion. To improve the pulse quality, a spectral filter is employed in the model. The simulation results show that spectral filtering could improve the pulse quality and shorten the pulse duration. Meanwhile, the optimum filter bandwidth is studied.     

Experimental study of pulse compression in a side-pumped Yb-doped double-clad mode-locked fiber laser

We have developed a side-pumped passively mode-locked Yb-doped double-clad fiber laser emitting sub-picosecond pulses at around 1.05 μm. Mode locking is achieved through a polarization additive-pulse mode-locking technique and compression is obtained with a grating pair inserted in the cavity. We have investigated the compression properties of this laser. High-energy pulses are emitted and different behaviors are observed, such as sideband generation, secant-like or Gaussian-like pulse emission. Received: 7 May 2001 / Revised version: 13 November 2001 / Published online: 17 January 2002     

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.     

Reflective carbon nanotube as the saturable absorber for mode-locked 1064 nm laser

With a reflective single-walled carbon nanotube as the saturable absorber, a laser diode-pumped passively mode-locked Nd:YVO₄ laser at 1064 nm was realized for the first time. The pulse duration of 12 ps was produced with a repetition rate of 83.7 MHz. The peak power and the single pulse energy of the mode-locking laser were 1.28 kW and 15.4 nJ, respectively.     

氧化石墨烯被动锁模掺镱光纤激光器多脉冲现象的实验研究

利用氧化石墨烯作为可饱和吸收体,在被动锁模全正常色散掺镱光纤激光器中研究了多脉冲的现象,在同一抽运功率不同偏振态下,实验获得了矩形脉冲谐波锁模、耗散孤子谐波锁模、准谐波锁模,脉冲峰值周期性调制,脉冲簇、脉冲束、混沌多重脉冲的多脉冲现象,插入激光腔内的2nm窄带滤波器具有限制增益带宽、对脉冲塑形、诱导多脉冲产生的作用,调节偏振控制器相当于改变腔内增益,是实现不同类型多脉冲现象的主要原因,本实验研究有利于加深对多脉冲动力学行为在正常色散区域氧化石墨烯锁模掺镱光纤激光器中的理解。     

High pulse energy mode-locked multicore photonic crystal fiber laser

A high pulse energy passively mode-locked fiber laser operating in the all-normal dispersion regime is demonstrated. The gain material is an Yb-doped multicore photonic crystal fiber with 18 cores in array-type geometry. Robust and self-starting mode locking is achieved using a fast semiconductor saturable absorber mirror. The laser generates 180?nJ chirped pulses at a 14.48?MHz repetition rate for an average power of 2.6?W. The 1.15?ps output pulses are compressed to 690?fs outside the cavity.     

基于全保偏八字腔结构锁模的光纤激光器及其功率放大

采用包层泵浦的全保偏八字腔结构搭建了一种脉宽可调的掺镱锁模光纤激光器,实现了中心波长为1 064nm、重复频率为4.683 MHz、脉冲宽度可调范围为0.8~5ns、对应平均功率范围为74.8~429.7mW的耗散孤子共振方波脉冲输出.腔内无需偏振控制器,仅通过调节泵浦输入即可实现锁模状态的自启动,并能够长时间保持稳定,在剧烈振动条件下亦不会失锁.采用两级光纤放大器进行功率放大,实现了100 W的平均功率输出,峰值功率高达26.68kW.     

Binding widely-separated pulses with a passively mode-locked Yb-doped double-clad fiber laser

We have investigated the generation of widely-separated bound pulses with a high power passively mode-locked Yb-doped double clad fiber laser. We report on the emission of bound pulses of 5 ps whose separation can exceed 180 ps. Pulses are further compressed extra-cavity to 140 fs, leading to pulse separations that can reach approximately 1300 pulse widths, while pulses remain bound. Scenarios leading to these regimes are detailed. RF analysis shows an important reduction of the amplitude noise of the laser when pulses bind together. Finally, we report on a new regime of multiple pulse emission of this fiber laser: stable co-emission of a single-pulse and a pair of bound pulses in the same cavity round trip. PACS 42.55.Wd; 42.65.Re