Harmonically pump a femtosecond optical parametric oscillator to 1.13 GHz by a femtosecond 515 nm laser

We demonstrate a harmonically pumped femtosecond optical parametric oscillator(OPO)laser using a frequency-doubled mode-locked Yb:KGW laser at a repetition rate of 75.5 MHz as the pump laser.Based on a bismuth borate nonlinear crystal,repetition rates up to 1.13 GHz are realized,which is 15 times that of the pump laser.The signal wavelength is tunable from 700 nm to 887 nm.The maximum power of the signal is 207 m W at the central wavelength of 750 nm and the shortest pulse duration is 117 fs at 780 nm.The beam quality(M^2 factor)in the horizontal and vertical directions of the output beam are 1.077 and 1.141,respectively.     

Toward higher-order passive harmonic mode-locking of a soliton fiber laser

We report >13 MHz/mW pump power efficiency in increasing the repetition rate of passive harmonic mode-locking by engineering the soliton pulse energy in Er fiber lasers incorporating carbon nanotube saturable absorber. Stable pulses with a ～5 GHz repetition rate and 40 dB of super-mode suppression are demonstrated with only ～400 mW pump power in a single-clad fiber laser.     

Er3+-Yb3+共掺杂光纤环型腔被动谐波锁模激光器

 报道了Er³⁺-Yb³⁺共掺杂光纤作为增益介质的环型腔光纤激光器。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,通过调整泵浦功率,调节偏振控制器的状态,实现了连续基波锁模和高阶谐波锁模两种稳定的锁模运转状态。其中连续基波锁模重复频率15.89 MHz,中心波长为1.557 nm,光谱宽度为9.9 nm。二阶谐波锁模重复率为31.79 MHz,三阶谐波锁模脉冲重复率为46.99 MHz。观察到了调Q锁模和调Q脉冲序列,给出了各种运转状态的实验结果并对多种锁模机理作了简要的分析。     

High repetition rate all-normal dispersion Yb:fiber laser for minimum pulses

Simulation and experimental results for high repetition rate all-normal dispersion Yb:fiber ring lasers are demonstrated for the cavity dispersion from 0.01 to 0.025 ps 2 .The simulation shows that the pulse spectrum has the potential to reach>30 nm for the dispersion of 0.014 ps 2 under practical pump power. This potential is proved by the experiment.Maximum spectral width of 30 nm is achieved at the repetition rate of 285 MHz under the 850-mW pump power.Average output power is 550 mW and dechirped pulse is 78 fs.     

宽光谱全正色散锁模掺镱光纤激光器

介绍了一种全正色散宽光谱被动锁模掺镱光纤激光器,利用非线性偏振旋转技术实现全正色散掺镱光纤激光器的被动锁模.当泵浦功率输出为500mW时,激光脉冲输出功率大于139mW,重复频率约为28.1MHz,脉冲宽度为3.8ps.为了进一步研究全正色散光纤激光器的宽光谱输出特性,在腔内熔接50m单模光纤,同时去除双折射滤波片,在泵浦功率为500mW时,观察到稳定锁模单脉冲耗散孤子,光谱范围为1 005~1 140nm,输出激光脉冲最大平均功率为90mW,重复频率为3.58MHz,脉冲宽度为519ps.     

Diode-Pumped Passively Mode-Locked 1079 nm Nd:CaGdAlO_4 Laser

We demonstrate a diode-pumped passively cw mode-locked NdiCaGdAlO_4 laser operating at 1079 nm with a semiconductor saturable absorber mirror for the first time to the best of our knowledge.The threshold pump power of the laser is 180 mW.A maximum average output power of 93 mW is obtained under the pump power of1.94 W.The pulse duration of the mode-locked pulses is 3.1 ps and the repetition rate is 157 MHz.     

用半导体可饱和吸收镜进行LD泵浦Yb∶YAG 激光器被动锁模研究

采用不同的半导体可饱和吸收镜, 实现了940 nm半导体直接泵浦Yb∶YAG激光器被动锁模, 得到了输出中心波长分别在1030 nm和1050 nm, 光谱半宽（FWHM）分别为1 nm和2 nm的稳定锁模脉冲序列, 其重复频率分别为190.24 MHz和178.6 MHz. 泵浦光为4W时, 两种波长的平均输出功率分别为80 mW和60 mW.     

自锁模Cr：LiSAF激光器的实验研究

以功率为９００ｍＷ，波长为４８８ｎｍ的单线氩离子激光作为泵浦源，在腔内不加任何主动调制器和可饱和吸收体的情况下实现了Ｃｒ：ＬｉＳＡＦ激光器的飞秒级自锁模运转，得到了脉冲宽度为４０ｆｓ，重复频率为１００ＭＨｚ，平均输出功率为４５ｍＷ的稳定的锁模脉冲序列。     

2.5-GHz repetition-rate singly resonant optical parametric oscillator synchronously pumped by a mode-locked diode oscillator amplifier system

We report on an optical parametric oscillator (OPO) that is synchronously pumped directly by a diode laser. This laser is an actively mode-locked master-oscillator power-amplifier system that produces 20-ps pulses at 927 nm with a repetition rate of 2.5 GHz and an average power of 0.9 W. The OPO, which is a singly resonant device based on periodically poled lithium niobate, generates 7.8-ps pulses. The OPO threshold is 300 mW of average pump power, and the maximum average idler output power is 78 mW at a wavelength of 2100 nm. By changing the crystal temperature we can wavelength tune the output in the ranges 1530-1737 nm (signal) and 1986-2348 nm (idler). Rapid wavelength tuning of the OPO over 46 nm (signal) and 74 nm (idler) is achieved through tuning the cavity length over 28 microm by use of a piezoelectric transducer.     

Wideband All-Polarization-Maintaining Yb-Doped Mode-Locked Fiber Laser Using a Nonlinear Optical Loop Mirror

We report on a wide-band and stable mode-locked all-polarization-maintaining fiber iaser configuration using a noniinear optical loop mirror.The central wavelength of the laser is 1080.14 nm and the 3dB bandwidth is 20.29 nm.The repetition rate of the pulse is 3.28 MHz and the pulse width is 848 ps.By tuning the pump power,which is centered at 980 nm,from 300 mW to 380 mW,we obtain a linearly changed output power from 6mW to 7.12 mW.The all-polarization-maintaining fiber configuration is fundamental to the stability of the output power.     

Highly stable, passively mode-locked fiber laser with low pump power for subpicosecond pulse generation

We present the design of highly stable, passively mode-locked fiber lasers which are based on a simple configuration and require a low pump power for the generation of optical pulses with subpicosecond pulsewidth. Our designed fiber laser uses a semiconductor saturable absorber mirror to realize the self-starting, passive mode locking at a low pump power of 29 mW, with which a stable optical pulse train is obtained at the fundamental repetition rate of 52.5 MHz and the central wavelength of 1557 nm. The output mode-locked optical pulses have a pulsewidth of 881 fs and an average output power of 1.78 mW, respectively.     

Mode-locked thulium-doped fiber laser based on 0.3 nm diameter single-walled carbon nanotubes at 1.95 μm

Employing 0.3 nm diameter single-walled carbon nanotubes(SWCNTs)as saturable absorbers,we demonstrate a passively mode-locked fiber laser operating at 1950 nm.The 0.3 nm diameter SWCNTs are prepared by pyrolyzing dipropylamine in the channels of zeolite crystals Mg APO-11(AEL).The laser pumped by a 1550 nm laser source produces 972 fs pulses with a spectral width at half-maximum of 4.2 nm and a repetition rate of 21.05 MHz,an average output power of 2.3 mW corresponding to the maximum pump power of 420 mW with a 10%output coupler.     

Cavity dumping of neodymium-doped fibre lasers using an acoustooptic modulator

We report high-repetition-rate pulses obtained by cavity dumping of a neodymium-doped phosphate glass fibre laser operating at 1053 nm using a specially constructed acoustooptic modulator. With 27 mW absorbed pump power at 812 nm we obtained stable trains of output pulses with repetition rate in the range 0.5 to 8 MHz having corresponding pulse widths in the range 127 to 19 ns without significant sacrifice in the average output power of 8 mW.     

Record low-power all-optical semiconductor switch operation at ultrafast repetition rates above the carrier cutoff frequency

The switch repetition-rate limit of all-optical semiconductor switches, for which the dynamic extinction ratio decreases with increasing repetition rate, is examined and overcome. The extinction ratio is improved by optimization of the interferometer phase bias, which has previously been set to pi. The extinction-ratio increase accompanies a drastic change in the output pulse spectrum. Both the output pulse profiles and the spectra, before and after optimization, are successfully reproduced by simulation. As a result, switch repetition of 42 GHz (2.5 times higher than the semiconductor-carrier cutoff frequency) is achieved by use of 5-ps, 1548-nm pump pulses. What are believed to be record low input pump-pulse energies of 750 aJ (peak power, 140microW) at 10 GHz and 6 fJ (1.1 mW) at 42 GHz are used.     

Intracavity terahertz-wave generation in a synchronously pumped optical parametric oscillator using quasi-phase-matched GaAs

We generated 1 mW of average output power at 2.8 THz (bandwidth of approximately 300 GHz) in a diffraction-limited beam by placing a 6-mm-long quasi-phase-matched GaAs crystal inside the cavity of a synchronously pumped optical parametric oscillator (OPO). The OPO used type-II-phase-matched periodically poled lithium niobate as a gain medium and was pumped by a mode-locked laser at 1064 nm, with a 7 ps pulse duration, 50 MHz repetition rate, and 10 W average output power. The terahertz radiation was generated by difference frequency mixing between the signal and idler waves of the near-degenerate doubly resonant OPO.     

Yb-doped strictly all-fiber laser actively Q-switched by intermodal acousto-optic modulation

We show an actively Q-switched ytterbium-doped strictly all-fiber laser. Cavity loss modulation is achieved in a tapered optical fiber by core-to-cladding mode-coupling induced by travelling flexural acoustic waves. When the acoustical signal is switched-off, the optical power losses within the cavity are reduced, and then a laser pulse is emitted. Trains of Q-switched pulses were successfully obtained at repetition rates in the range 1–10 kHz, with pump powers between 59 and 88 mW, at the optical wavelength of 1064.1 nm. Best results were for laser pulses of 118 mW peak power, 1.8 μs of time width, with a pump power of 79 mW, at 7 kHz repetition rate.     

Transition Metal Dichalcogenides (WS_2 and MoS_2) Saturable Absorbers for Mode-Locked Erbium-Doped Fiber Lasers

We demonstrate an ultrafast fiber laser based on transition metal dichalcogenide materials which are tungsten disulfide(WS2) and molybdenum disulfide(MoS_2) as saturable absorber(SA). These materials are fabricated via a simple drop-casting method. By employing WS_2, we obtain a stable harmonic mode-locking at the threshold pump power of 184 mW, and the generated soliton pulse has 3.48 MHz of repetition rate. At the maximum pump power of 250 mW, we also obtain a small value of pulse duration, 2.43 ps with signal-to-noise ratio(SNR) of 57 dB.For MoS_2 SA, the pulse is generated at 105 mW pump power with repetition rate of 1.16 MHz. However, the pulse duration cannot be detected by the autocorrelator device as the pulse duration recorded is 468 ns, with the SNR value of 35 dB.     

High-power synchronously pumped AgGaS(2) optical parametric oscillator

Greater than 2 W of average power was generated in the infrared region by a AgGaS(2) optical parametric oscillator (OPO). A Q -switched mode-locked laser was used to pump the OPO synchronously. Tunability from 1.4 to 1.9mum and a maximum output power of 750 mW at 1.44mum were achieved with a standing-wave cavity. Redesigning the cavity into a ring configuration allowed the depleted pump, signal, and idler beams to be extracted efficiently through separate mirrors. This design generated signal and idler beams of high spatial quality at respective power levels of 1.5 and 620 mW at a pulse repetition rate of 2 kHz.     

被动锁模Yb3+光纤环形腔激光器的研究

 采用974 nm半导体激光器作为泵浦源，超高掺杂Yb³⁺光纤作为增益介质，利用光纤的非线性偏振旋转效应，得到稳定的ps量级锁模光脉冲。泵浦功率220 mW时，激光器锁模阈值功率150 mW，输出功率26 mW，锁模光脉冲中心波长1 046 nm，3 dB带宽6.01 nm，20 dB带宽16 nm，脉宽22 ps，重复频率20 MHz。与同类光纤激光器相比，该激光器输出功率高，具有更好的稳定性。     

基于石墨烯的1 064 nm连续锁模超短脉冲激光器

介绍了利用沉积在增透镜上的石墨烯薄膜作为可饱和吸收体、808 nm激光二极管端面泵浦Nd∶YVO4晶体的1 064 nm连续锁模激光输出特性。采用W型折叠谐振腔结构,在808 nm泵浦功率为8.0 W时,有稳定的连续锁模脉冲输出,平均输出功率达到185 mW;当抽运功率增加到16.0 W时,获得了中心波长1 063.4 nm、脉冲宽度为518 fs、重复频率为66.7 MHz、最大平均输出功率为323 mW的百飞秒量级超短脉冲激光输出。实验结果表明:石墨烯具有优良的可饱和吸收性,在1 064 nm波段能够实现高功率、百飞秒量级连续锁模脉冲激光输出。