High-power diode-pumped Yb3+:CaF2 femtosecond laser

We report what is believed to be the first demonstration of a high-power passively mode-locked diode-pumped femtosecond laser based on an Yb3+:CaF2 single crystal, directly pumped by a 15-W fiber-coupled laser diode. With a 5-at. % Yb3+ -doped sample and prisms for dispersion compensation we obtained pulses as short as 150 fs, with 880 mW of average power and up to 1.4-W average output power, with a pulse duration of 220 fs, centered at 1049 nm. The laser wavelength could be tuned from 1040 to 1053 nm in the femtosecond regime. Using chirped mirrors for dispersion compensation, the oscillator provided up to 1.74 W of average power, with a pulse duration of 230 fs, corresponding to a pulse energy of 20 nJ and a peak power of 85 kW.     

Diode-pumped mode-locked Yb:YCOB laser generating 35 fs pulses

Direct sub-50-fs pulse generation is demonstrated with a mode-locked Yb:YCa4O(BO3)3 laser. With external compression, pulses as short as 35 fs are generated at 1055 nm. The oscillator operating at a repetition rate of 95 MHz is pumped by a two-section distributed Bragg reflector tapered diode laser and mode locked by a semiconductor saturable absorber mirror. The onset of self-Raman-conversion for pulse spectral bandwidths exceeding 40 nm (FWHM) is observed.     

基于微纳光纤-单壁碳纳米管可饱和吸收体的被动调Q掺镱光纤激光器

为实现具有高脉冲能量的调Q脉冲激光输出,利用微纳光纤-单壁碳纳米管复合的方法制备可饱和吸收体,并对基于该类型可饱和吸收体器件的被动调Q掺镱光纤激光器进行研究。采用拉伸法将普通单模石英光纤拉制成微纳光纤,将其与单壁碳纳米管溶液复合,进一步制备成全光纤集成型器件。将该器件置于环形腔掺镱光纤激光器中,利用976 nm半导体激光器作为抽运源。当抽运功率为53 mW时,实现了调Q脉冲激光输出,激光中心波长为1 039 nm。进一步提升抽运功率至76 mW,可获得脉冲宽度为3.1μs、重复频率为25.5 kHz、单脉冲能量为941nJ的调Q脉冲激光输出。研究表明,利用微纳光纤制备的可饱和吸收体器件具有较高的损伤阈值,可用于实现高脉冲能量的激光输出。     

Theoretical and experimental investigations of quasi-continuous wave diode array side-pumped Yb＇YAG slab laser

An analytical model of quasi-continuous wave (quasi-CW) diode array side-pumped slab laser for Yb:YAG oscillator in long-pulse free-running has been developed based on the CW model. In this model we first introduce a new parameter, pump pulse width, and make the model available for use in the quasi-CW model. We also give an analytical equation of laser delay time to calculate the laser pulse width. A detailed model is also presented for a new structure laser design, taking account of the geometry of Yb:YAG slab. A quasi-CW diode array side-pumped Yb:YAG slab laser is investigated theoretically and experimentally. Experiments yield a quasi-CW output energy up to 20.36 mJ with the laser pulse width of 654.55 μs at 1049 nm when the diode arrays operate at 25 Hz and 1 ms pulse width. The crystal dimensions are 3 mm×8 mm×1 mm and the doping density is 10 at.%. The experimental results are in good agreement with the predictions of the theoretical model.     

Diode-pumped continuous-wave and femtosecond laser operations of a heterocomposite crystal Yb3+: SrY4(SiO4)3O parallel Y2Al5O12

We report cw and femtosecond laser operations under diode pumping of a diffusion-bonding heterocomposite Yb-doped crystal: Yb3+:SrY4(SiO4)3O parallel Y2Al5O12(YAG paralell SYS:Yb). To show the advantages of this heterocomposite crystal over classical Yb:SYS crystal, we first investigate the high-power cw regime. A cw power of 4.3 W is demonstrated. The femtosecond regime is also investigated, and 1-W-average-power, 130-fs pulses at 1070 nm are produced, which represents, to our knowledge, the first demonstration of an Yb-doped heterocomposite mode-locked laser.     

Generation of 2-nJ pulses from a femtosecond ytterbium fiber laser

We report a mode-locked ytterbium fiber laser that generates femtosecond pulses with energies as large as 2.2 nJ. This represents a 20-fold improvement in pulse energy compared with that of previously reported femtosecond Yb fiber lasers. The laser produces pulses as short as 52 fs, which are to our knowledge the shortest pulses to date from a Yb fiber laser. The laser is diode pumped by a wavelength-division multiplexing coupler, which leads to excellent stability.     

Highly efficient mode-locked Yb:Sc2O3 laser

Passive mode locking of the Yb:Sc2O3 laser is demonstrated. We investigate the laser performance with Ti:sapphire and diode-laser pumping. The laser is mode locked by use of a semiconductor saturable-absorber mirror and emits as much as 0.8 W of power in the picosecond range with a pump efficiency as high as 47%. With dispersion compensation, pulses as short as 230 fs for an average power of 0.54 W are obtained at 1044 nm. This is, to our knowledge, the first femtosecond oscillator based on an Yb-doped sesquioxide crystal.     

A 12.1-W SESAM mode-locked Yb:YAG thin disk laser

Pumped by a 940 nm fiber-coupled diode laser, a passively mode-locked Yb:YAG thin disk oscillator was demonstrated with a semiconductor saturable absorber mirror(SESAM). 12.1 W mode-locked pulses were obtained with pulse duration of 698 fs at the repetition rate of 57.43 MHz. Measurement showed that the beam quality was close to the diffraction limit.     

微型化LD泵浦Er~(3+),Yb~(3+)共掺磷酸盐玻璃被动调Q激光器

报道了一种主要应用于激光测距的微型化激光二极管泵浦Er3+/Yb3+共掺磷酸盐玻璃被动调Q激光器。采用中心波长940nm的二极管作为泵浦源,Er3+/Yb3+共掺磷酸盐玻璃作为增益介质,Co2+:MgAl2O4作为被动调Q晶体,通过优化增益介质和被动调Q晶体参数,获得了最佳的增益介质长度和被动调Q晶体初始透过率。当泵浦能量14mJ,重复频率10Hz,泵浦脉宽5ms时,获得了单脉冲能量480μJ,脉宽5ns,峰值功率大于20kW的激光输出,激光光束质量因子为1.2。     

Yb3+:Y2O3透明陶瓷激光器获得5 W连续激光输出

用带尾纤输出的激光二极管作为抽运源,采用端面抽运10％Yb^3 ：Y2O3多晶透明陶瓷的方式获得了连续激光输出。抽运阈值功率为5．6W,当陶瓷介质吸收的抽运功率为31．11W时,Yb^3 ：Y2O3多晶透明陶瓷获得了最大连续激光输出功率5．48W。光—光转换效率为17．6％,斜率效率为25％。同时在激光实验过程中,没有发现饱和现象,因此采用更高功率的激光二极管作为抽运源,陶瓷的激光输出功率会得到进一步提高。这一研究成果表明,多晶透明陶瓷是一种非常有潜力的激光增益介质。     

A passively Q-switched diode pumped Yb:YAG microchip laser

A passively Q-switched diode pumped Yb:YAG microchip laser with Cr4+:YAG saturable absorber mirror is reported. The TEMoo laser pulses are obtained with 1,7-uJ pulse energy, 15-ns pulse width, 0.11-kW peak power, and a repetition rate of 2.2 kHz at 1049 nm. The doped concentration and dimension of Yb:YAG microchip crystal are 10 at.-% and 5×0.6 mm2, respectively.     

High-power 200 fs Kerr-lens mode-locked Yb:YAG thin-disk oscillator

We demonstrate a power-scalable Kerr-lens mode-locked Yb:YAG thin-disk oscillator. It delivers 200 fs pulses at an average power of 17 W and a repetition rate of 40 MHz. At an increased (180 W) pump power level, the laser produces 270 fs 1.1 μJ pulses at an average power of 45 W (optical-to-optical efficiency of 25%). Semiconductor-saturable-absorber-mirror-assisted Kerr-lens mode locking (KLM) and pure KLM with a hard aperture show similar performance. To our knowledge, these are the shortest pulses achieved from a mode-locked Yb:YAG disk oscillator and this is the first demonstration of a Kerr-lens mode-locked thin-disk laser.     

Diode-pumped Kerr-lens mode-locked femtosecond Yb:YAG ceramic laser

We experimentally demonstrated a diode-pumped Kerr-lens mode-locked femtosecond laser based on an Yb:YAG ceramic. Stable laser pulses with 97-fs duration, 2.8-nJ pulse energy, and 320-mW average power were obtained. The femtosecond oscillator operated at a central wavelength of 1049 nm and a repetition rate of 115 MHz. To the best of our knowledge, this is the first demonstration of a Kerr-lens mode-locked operation in a diode-pumped Yb:YAG ceramic laser with sub-100 fs pulse duration.     

Microsecond pulsed optical parametric oscillator pumped by a Q-switched fiber laser

We report on what is to our knowledge the first optical parametric oscillator (OPO) pumped by microsecond pulses from a wavelength-tunable solid-state laser. The singly resonant OPO (SRO) is based on a periodically poled LiNbO3 crystal and pumped with 2.1-micros-long pulses from an actively Q-switched Yb fiber laser. At an average fiber laser power of 3.6 W, the SRO generates 1.9-micros-long pulses with a repetition rate of 25 kHz and an average power of 560 mW at 3360 nm. The SRO was tuned from 1518 to 1634 nm (signal) and from 3145 to 3689 nm (idler) via the crystal temperature and poling period. By all-electronic tuning of the fiber laser wavelength over 19 nm, tuning of the mid-infrared idler wavelength over 195 nm was achieved.     

Femtosecond oscillator on Yb:KYW crystal pumped by laser diode with fiber output

A femtosecond laser based on an Yb:KYW crystal with direct longitudinal pumping by a high-power semiconductor injection laser with a fiber output is described. Femtosecond pulses were generated in the self-longitudinal-mode-locking operating condition due to the use of a semiconductor saturable absorber. The average power of the oscillator was as high as 3.5 W at a central wavelength of 1035 nm, the pulse length and pulse repetition rate being 200 fs and 85.5 MHz, respectively. The product of the pulse length and the radiation spectrum width was 1.3 times higher than the theoretical limit for the pulse shape described by the function sech². The designed master oscillator can be also used as a stand-alone source of femtosecond radiation pulses for material microprocessing and primary source for femtosecond laser amplification systems.     

YAG晶体中Cr4+和Yb3+的光谱和荧光特性研究

报道了（Ｃｒ＾４＋,Ｙｂ＾３＋）：ＹＡＧ晶体的吸收光谱和荧光光谱特性。在室温下,（Ｃｒ＾４＋,Ｙｂ＾３＋）：ＹＡＧ晶体在９３７ｎｍ和９６８ｎｍ处存在两个吸收带,能与ＩｎＧａＡｓ激光二级管有效耦合：而且在１０３０ｎｍ处有一Ｃｒ＾４＋吸收峰,可以实现对Ｙｂ＾３＋的自调Ｑ激光输出。（Ｃｒ＾＋,Ｙｂ＾３＋）：ＹＡＧ 荧光光谱与Ｙｂ＾３＋：ＹＡＧ晶体一样,发光中心也是位于１０２９ｎｍ,但其强度比Ｙｂ＾３＋：     

A 61-mJ, 1-kHz cryogenic Yb: YAG laser amplifier

We report a diode-pumped rod-type Yb:YAG laser amplifier operating at 1 kHz. Cryogenic cooling method was adopted to make the Yb:YAG crystal work with four-level behavior. A single-frequency fiber laser acts as the seed in an actively Q-switched Yb:YAG oscillator. The resonator delivers 5.75-mJ pulses at 1 kHz with a pulse duration of approximately 40 ns. The pulses were amplified to 61 mJ in a four-pass rod-type Yb:YAG amplifier with optical-to-optical efficiency of 24% in the main amplifier. The M² parameter of the output laser is <1.4.     

掺镱硼酸钙氧钇飞秒激光器及在拉锥光纤中产生跨倍频程超连续光

跨倍频程超连续光谱的产生是光学频率梳系统中测量载波包络相移频率的关键.本文采用拉锥单模光纤作为非线性光谱展宽介质, 将半导体激光(LD)抽运的掺镱硼酸钙氧钇(Yb:YCOB)振荡器输出的飞秒激光耦合到该拉锥光纤中, 通过飞秒激光在光纤中发生的相位调制、四波混频等非线性效应将光谱展宽至超过倍频程的范围.振荡器输出的飞秒激光脉冲宽度为130 fs, 中心波长为1052 nm, 重复频率为76.8 MHz, 平均功率为620 mW, 耦合进单模拉锥光纤后获得了光谱覆盖范围从550 nm至1350 nm的跨倍频程超连续光谱, 最大输出平均功率为323 mW, 耦合效率达到52%.为进一步实现全固态飞秒激光光学频率梳提供了重要基础.     

High-power tunable diode-pumped Yb3+:CaF2 laser

Results of diode-pumped cw laser operation of an Yb3+:CaF2 single crystal are reported for what is to our knowledge the first time. With a 5-at.% Yb3+ -doped sample we obtained 5.8-W output power at 1053 nm for 15 W of incident power at 980 nm. The laser wavelength could be tuned from 1018 to 1072 nm, and a small-signal gain as high as 1.8 was achieved, showing the great potential of Yb3+:CaF2 as an amplifier medium for femtosecond pulses.     

Femtosecond diode laser MOPA system at 920 nm based on asymmetric colliding pulse mode-locking

We report on the generation of 267 fs long pulses with a peak power of 661 W emitted by an InGaAs diode laser master-oscillator power-amplifier (MOPA) system with an external grating compressor. The oscillator emits strongly chirped picosecond pulses with several nanometer of bandwidth, which can be amplified without significant phase modulation and are compressed to femtosecond pulses after leaving the amplifier. We used a diode laser module for asymmetric colliding pulse mode-locking and optimized the collision point and the relative intensity of the counter-propagation pulses.