Passively mode-locked Yb3+:Sc2SiO5 laser with reflection-type single-walled carbon nanotube absorber

A reflection-type single-walled carbon nanotube saturable absorber fabricated by a vertical evaporation method was to our knowledge first used in a passively mode-locked Yb(3+):Sc(2)SiO(5)(Yb:SSO) laser. The laser operated at a repetition frequency of 94 MHz with a central wavelength of 1062.6 nm. A short pulse duration of 1.8 ps was produced with an average power of 349 mW; and the highest pulse energy of 3.7 nJ, corresponding to its maximum peak power, can reach 2.1 kW.     

163 fs被动锁模掺Er~(3+)光纤激光器

研制了一种采用非线性偏振旋转锁模效应的被动锁模掺Er3+飞秒激光器。利用性能稳定的980 nm激光二极管(LD)作为抽运光源,以高掺杂Er3+光纤为增益介质,在抽运功率为650 m W时,激光器锁模输出重复频率为31.25 MHz、平均输出功率为70 m W、中心波长为1565 nm、光脉冲宽度为163 fs的稳定飞秒脉冲激光。该激光器易于操作和调节,并且锁模状态稳定可以长时间的运行,其光纤结构更有利于小型化和便携化。     

157 W all-fiber high-power picosecond laser

An all-fiber high-power picosecond laser is constructed in a master oscillator power amplifier configuration. The self-constructed fiber laser seed is passively mode locked by a semiconductor saturable absorber mirror. Average output power of 157 W is obtained after three stages of amplification at a fundamental repetition rate of 60 MHz. A short length of ytterbium double-clad fiber with a high doping level is used to suppress nonlinear effects. However, a stimulated Raman scattering (SRS) effect occurs owing to the 78 kW high peak power. A self-made all-fiber repetition rate increasing system is used to octuple the repetition rate and decrease the high peak power. Average output power of 156.6 W is obtained without SRS under the same pump power at a 480 MHz repetition rate with 0.6 nm line width.     

Ultrafast Yb:Y₂SiO₅ laser investigation based on a carbon nanotube absorber

Transmission-type single-walled carbon nanotube saturable absorbers were successfully fabricated and used in a CW passively mode-locked Yb:Y?SiO? laser for the first time to our knowledge. We obtained pulses as short as 1.1 ps around a center wavelength of 1058 nm. The average output power of 1.1 W was achieved at the repetition of 96.7 MHz; the corresponding peak power and energy of a single pulse was 10.3 kW and 11.4 nJ, respectively.     

Diode-pumped passively mode-locked Nd:YAG laser at 1338 nm with a semiconductor saturable absorber mirror

We demonstrate a diode-end-pumped passively mode-locked 1338 nm Nd:YAG laser with a semiconductor saturable absorber mirror. At the absorbed pump power of 8.89 W, an average output power of 1.12 W was obtained with a slope efficiency of 14%. The pulse width was 22.4 ps with a repetition rate of 63.9 MHz, corresponding to a peak power of 782 W. In addition, the bandwidth of the mode-locking spectrum is as narrow as 20.44 GHz, which shows the potential application in long-distance ranging and fiber information transmission because of the low dispersion of these ultrashort pulses.     

Compact, stable 1 GHz femtosecond Er-doped fiber lasers

We demonstrate a high-repetition-rate soliton fiber laser that is based on highly doped anomalously dispersive erbium-doped fiber. By splicing an 11 mm single-mode fiber to the erbium-doped fiber, the thermal damage of the butt-coupled saturable Bragg reflector (SBR) is overcome. The laser generates 187 fs pulses at a repetition rate of 967 MHz with a measured long-term stability of more than 60 h.     

全光纤结构超短脉冲光纤放大器

本文利用掺Yb光纤的非线性偏振旋转效应搭建了光纤环形腔激光器,通过改变增益光纤的长度和耦合器输入输出的比例,对其进行优化,获得了稳定的自启动锁模脉冲,并以此作为种子源,采用主振荡功率放大MOPA全光纤结构,以双包层掺Yb光纤为增益介质实现了对种子源信号光的放大,获得了平均功率2.042W、中心波长1063.8 nm、重...     

MEH-PPV organic material as saturable absorber for Q-switching and mode-locking applications

ABSTRACT

Q-switched and mode-locked pulse generation in Erbium-doped fiber lasers (EDFLs) are demonstrated using Poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) organic semiconductor material as a saturable absorber (SA) for the first time. The MEH-PPV was prepared in the form of a thin film having a modulation depth of 12% and saturation intensity of 40?MW/cm². The SA was placed in a laser cavity to produce a stable Q-switched operating at 1564.0?nm. The maximum repetition rate of 78.62?kHz, minimum pulse width of 3.54?µs and maximum pulse energy of 59.45?nJ were attained at 125.2?mW pump power. On the other hand, by incorporating an additional 100?m long single mode fiber, the mode locked EDFL self-started as the pump power was raised above 125.2?mW. The soliton pulse was obtained due to the enhancement of the nonlinearity in the cavity. The mode-locked laser operated at 1568.5?nm with a fixed repetition rate of 1.859?MHz and pulse width of 2.97?ps.     

Wavelength switching in an actively mode-locked Fabry-Perot laser diode with a highly dispersive external cavity

We demonstrate a simple and reliable scheme for wavelength switching in an actively harmonic mode-locked Fabry-Perot laser diode (FPLD) that is coupled to a highly dispersive external fiber cavity. Wavelength switching between FPLD modes is achieved by detuning of the modulation frequency applied to the FPLD. A side-mode suppression ratio of as much as 40 dB is maintained, and the supermode noise suppression ratio is more than 50 dB for the whole wavelength switching operation range of 4.7 nm when the pulse repetition rate is ~2 GHz. The wavelength-switching mechanism of our laser is based on the wavelength-dependent cavity resonance frequency shift that is due to chromatic dispersion, and we verify that our experimental results closely coincide with analytical results.     

Compact Q-switched and mode-locked Nd³⁺:YVO₄/Cr⁴⁺:YAG self-Raman laser

Compact passively Q-switched and mode-locked Nd³⁺:YVO₄/Cr⁴⁺:YAG self-Raman laser with high mode-locked repetition rate was demonstrated. The picosecond first Stokes at 1176?nm was successfully obtained. At the maximum incident pump power, the average output power was 95?mW with the mode-locked pulse repetition rate of 940?MHz. Yellow laser output of 588.2?nm was also realized by the use of LiB₃O₅ frequency doubling crystal.     

Supercontinuum generation from a sub-megahertz repetition rate femtosecond pulses based on nonlinear polarization rotation technique

A means of supercontinuum (SC) generation is proposed and demonstrated, using femtosecond mode-locked pulses with sub-megahertz repetition rate based on the nonlinear polarization rotation technique. Total cavity length is approximately 522?m, which includes an additional 500?m single mode fiber (SMF) and the fundamental repetition rate obtained is 404.5?kHz. The mode-locked spectrum has a central wavelength of approximately 1600?nm and a 3?dB bandwidth of 16?nm, which falls within the L-band region. The threshold power for the mode-locked operation is achieved at approximately 52?mW. At pump power of 74?mW, the measured pulse width, pulse energy, and average output power are 70?fs, 18.3?nJ and 7.4?mW respectively. The generated pulses are amplified by a 72.44?mW erbium-doped fiber amplifier before being injected into a 100?m long highly non-linear fiber as the nonlinear medium to generate the SC spectrum. The obtained SC spectrum spans from 1250?nm to more than 1700?nm, with bandwidths of 450?nm at a ?70?dBm output power level. For comparison purpose, the 500?m SMF is removed from the setup and similar measurements are then repeated for this case.     

Cavity-length optimization for high energy pulse generation in a long cavity passively mode-locked all-fiber ring laser

In order to achieve higher pulse energy in a passively mode-locked fiber ring laser, a long cavity length is commonly implemented. However, a long cavity operating in the anomalous dispersion regime also leads to pulse broadening, which reduces the average pulse power. In this paper, the trade-off between cavity length and average pulse power is investigated with the aim of optimizing the cavity length to achieve maximum pulse energy. Numerical simulation results, presented here, indicate that there exists an optimum cavity length for which the pulse energy is maximum and the optimum length shifts as the pump power changes. The simulation results for a pump power of 500 mW are verified by measurements carried out on a long cavity nonlinear polarization rotation mode-locked all-fiber ring laser operating in the anomalous dispersion regime. With a repetition rate of 266 kHz for the dissipative solitons, we achieve a pulse energy of 139.1 nJ for a cavity length of 700 m. Higher pulse energy can be expected by using a pump laser diode with higher pump power.     

Passive mode-locking in erbium-doped fibre laser based on BN-GO saturable absorber

A C-band mode-locked fibre laser incorporating a boron nitride-doped graphene oxide (BN-GO)-based saturable absorber (SA) is proposed and demonstrated. The SA is fabricated by depositing multiple layers of synthesized BN-GO nanoparticles onto the polished surface of a side-polished fibre, which is then inserted into an erbium-doped fibre laser cavity to generate the desired pulsed output. The strong nonlinear optical response and light absorption of the BN-GO nanoparticles induces the generation of a highly stable mode-locked pulse at 1567.32?nm with visible Kelly’s sidebands. The pulses have a measured repetition rate of 13.56?MHz and a pulse width of 1.18?ps at the maximum pump power of 280.5?mW. The pulses have a frequency signal-to-noise ratio of ～53?dB, indicating a highly stable output. The proposed laser would find significant telecommunications applications, particularly for dense wavelength division multiplexing systems.     

Diode-pumped passively mode-locked Nd:GYSGG laser at 1061 nm with periodically poled LiNbO3 nonlinear mirror

ABSTRACT

We report a nonlinear-mirror mode-locked diode-pumped solid-state Nd:GYSGG laser operating at 1061?nm. The nonlinear mirror comprises a periodically poled LiNbO₃(PPLN) crystal and a dichroic mirror. Continuous-wave mode-locked laser with an output power of 450?mw is obtained under a diode pump power of 5.5?W at 808?nm. The repetition rate of the mode-locked laser is 97.1?MHz and the bandwidth of spectral is 1.3?nm. Considering the group velocity mismatch (GVM) of PPLN, we estimate the minimum pulse width is about 9?ps.     

Efficient versatile-repetition-rate picosecond source for material processing applications

We report on the development of an efficient and simple picosecond diode-pumped solid-state laser source with a versatile repetition rate (typically 1 Hz-1 MHz) for material processing applications. The laser source is based on a 4 MHz repetition rate mode-locked oscillator and a passive 3D multipass amplifier both based on Nd:YVO(4) crystals. Micromachining experiments were performed to study the influence of pulse energy on the machining quality for Al, Cu, paper, and glass.     

基于光纤延迟线的时间抖动测量系统

对飞秒激光器时间抖动的准确测量是推动其高精度应用的重要前提。为实现时间抖动的高精度、无参考测量,设计并搭建了一套基于光纤延迟线的测量系统。基于非对称迈克尔逊干涉仪的结构,在其中一臂引入一段长光纤延迟线鉴别时间误差,提高时间抖动测量精度。测量了一台实验室自制的重复频率为82 MHz的锁模光纤激光器的时间抖动功率谱,其在100 Hz~10 kHz的积分范围内RMS时间抖动为10.1 fs。     

Sequence lasing in a gain-switched Yb3+,Er(3+)-doped silica double-clad fiber laser

Experimental results relating to the gain-switched operation of a double-clad Yb3+,Er(3+)-doped silica fiber laser that is pulse pumped with the output from a flash-lamp-pumped Ti:sapphire laser are presented. For all the configurations of the fiber laser that we studied, the 2F5/2-->2F7/2 laser transition of the Yb3+ ion lased prior to laser emission from the 4I13/2-->4I15/2 transition of the Er3+ ion. To the best of our knowledge, this is the first reported operation of sequence lasing in the Yb3+,Er(3+)-codoped system. This succession of laser pulses deduced from the measurements of this investigation is a consequence of both the short intense pump pulse and the short 900-nm wavelength of the pump that does not overlap with any important excited-state absorption transitions. We believe that the predominant interionic interaction during the course of the pump pulse is the double-energy transfer to the Er3+ ion acting twice from the 2F5/2 energy level of the Yb3+ donor ion. A maximum total output of 1.65 mJ is obtained (1.38 mJ from the 2F5/2-->2F7/2 transition of Yb3+ and 0.27 mJ from the 4I13/2-->4I15/2 transition of Er3+) from a nonoptimized configuration of the fiber laser. The wavelength of the output from the fiber laser was measured to vary approximately linearly with fiber length from 1040 to 1046 nm for the Yb(3+)-based laser and 1535 to 1541 nm for the Er(3+)-based laser.     

Suppression of continuous lasing in a carbon nanotube polyimide film mode-locked erbium-doped fiber laser

We demonstrated an erbium-doped mode-locked fiber laser using a single-walled carbon nanotube-dispersed polyimide (SWNT-PI) film. Different mode-locking operations were compared and analyzed utilizing SWNT-PI films with different concentrations (2, 1, and 0.25 wt.%, respectively). It was found that the continuous single-pulse mode-locking operation was often accompanied by a continuous wave oscillation part for the 1 and 0.25 wt.% SWNT-PI films, whereas the 2 wt.% SWNT-PI film presented the most excellent mode-locking performance, thanks to sufficient modulation depth. Using the 2 wt.% SWNT-PI film, a stable pulse train with a pulse width of 840 fs and a repetition rate of 15.3 MHz was achieved. The average output power was 0.33 mW at the pump power of 155 mW under an output coupling ratio of 10%. Operational performance of the laser cavity when employing the 2 wt.% SWNT-PI film was also demonstrated.     

Diode-pumped passively mode-locked multiwatt Nd:GdVO4 laser with a saturable Bragg reflector

We report a first demonstration, to our knowledge, of a cw passively mode-locked Nd:GdVO4 laser (k = 1063 nm). A relaxed saturable Bragg reflector was used. The laser generates pulses of 9.2 ps at a repetition rate of 119 MHz. As much as 5.4 W of average power was realized with a slope efficiency of 25.7%.     

Passively Q-Switched Yb:YAG Laser with Cr(4+):YAG as the Saturable Absorber

By using a continuous-wave Ti:sapphire laser as a pumping source, we demonstrated a passively Q-switched Yb:YAG laser at room temperature with Cr(4+):YAG as the saturable absorber. We achieved an average output power of as much as 55 mW at 1.03 mum with a pulse width (FWHM) as short as 350 ns. The initial transmission of the Cr(4+):YAG has an effect on the pulse duration (FWHM) and the repetition rate of the Yb:YAG passively Q-switched laser. The Yb:YAG crystal can be a most promising passively Q-switched laser crystal for compact, efficient, solid-state lasers.