High-repetition tunable picosecond dye laser pumped by a copperbromide laser

It is reported that by mixing the saturable absorber DODCI with the gain medium Rh6G, 30-ps pulses can be generated from a short-cavity dye laser pumped by a copper bromide laser with a 25-ns pulsewidth and a 10-kHz repetition rate. A theoretical analysis of pulse shortening by this method is shown to agree with experimental results. A dispersion-amplifier system was employed for synchronous amplification and frequency tuning of the dye laser. The single-pulse energy was up to 0.15 μJ with a linewidth-of 1.0 cm^-1 in a one-stage amplifier, and the amplified spontaneous emission (ASE) background noise was reduced to below 10%. By simply rotating the grating and occasionally adjusting the thickness of the dye cavity slightly, the laser can be tuned continuously from 570 to 590 nm with a nearly Fourier-transform-limited linewidth. The repetition rate can be varied from 10 to 20 kHz     

Picosecond laser diode pulse amplification up to 12 W by laserdiode pumped erbium-doped fiber

Intense picosecond optical pulse generation from a gain-switched laser diode (LD) was demonstrated using a 1.48-μm LD-pumped Er³⁺ -doped fiber laser amplifier. Saturation characteristics of the amplifier output power were also measured as a function of input repetition frequency. An amplified peak power of 12 W and 105-pJ pulse energy were obtained for 9-ps pulses at a 33-GHz repetition frequency. This is the highest peak power yet demonstrated in pulse generation employing all-laser diodes as active devices     

低重复频率脉冲掺镱光纤放大器

为了研究低重复频率两级脉冲掺Yb3+光纤放大器,采用脉冲信号驱动的半导体激光器作为种子光源,产生重频100Hz、半峰全宽100ns、能量30nJ的矩形光脉冲。第1级放大采用单模掺Yb3+光纤放大器,双程放大方案有效地抑制了放大自发辐射,放大后的脉冲能量达到了8.2μJ。第2级放大采用纤芯直径15μm的双包层掺Yb3+光纤放大器,大功率多模半导体激光器连续抽运。结果在抽运功率为7.3W时,放大输出脉冲能量达到了242μJ,放大输出半峰全宽压缩为29ns。输出的光束质量较好,为准单模输出。结果表明,该光纤放大器输出脉冲能量高,具有全光纤化、结构简单的特点。     

Picosecond CO2 laser-pulse generation and amplification

The generation of 30-ps 10-μm laser pulses from an optical-free-induction-decay (OFID) 10-μm CO₂ laser system and the first realization of a UV-preionized high-pressure CO₂-laser-pulse amplifier with Ernst-electrode profiles for these ultrashort CO₂ laser pulses are described. For a given transverse electric discharge width, the Ernst profile makes it possible to position the UV-radiation sources nearer to the discharge than with the Rogowski or Chang profile. A more homogeneous preionization of the discharge area is possible. Thus, the amplifier works up to 15 bar with a laser-gas mixture of 5:5:90 (CO₂:N₂:He). The authors amplified 30-ps OFID 10-μm CO₂-laser pulses up to ten times by passing through the amplifier twice. Thus, 10-μm OFID pulse energies of 1 mJ were achieved. With the amplifier used as an oscillator, a maximum output energy of 600 mJ was obtained in longitudinal-multimode operation for 50-ns pulses     

Kilohertz gain-switched laser operation and femtosecondregenerative amplification in Cr:forsterite

We present a comprehensive study of the optimum operating regime in a gain-switched Cr:forsterite laser at a repetition frequency of 1 kHz with special attention to temperature-dependent and parasitic absorption effects and proper resonator design. On the basis of the results achieved, me demonstrate highly efficient (13% extraction efficiency) operation of a femtosecond regenerative amplifier based on Cr:forsterite and operating near room temperature with a novel BBO Pockels cell that is highly resistant to optical damage. Chirped pulse amplification raises the pulse energy to 355 μJ in ≈30 cavity round trips which corresponds to an amplification factor of ≈5.5×10⁵. The nearly transform limited 200-μJ 135-fs compressed pulses near 1.25 μm have a peak power of ≈1.5 GW. Frequency doubling with 52% conversion efficiency in LBO produces femtosecond pulses of 104-μJ energy in the visible near 625 nm     

Extreme chirped pulse oscillator (XCPO) using a theta cavity design

We demonstrate an extreme chirped pulse mode-locked laser, simultaneously generating near-transform-limited 3.9-ps optical pulses and /spl sim/510-ps linearly chirped output from the oscillator. The design overcomes fundamental limitations of energy extraction and nonlinearities induced by gain dynamics so that we can increase the dc current of the semiconductor optical amplifier up to 600 mA without distortion of the pulse characteristics. The maximum average power of the stretched pulses from the 1.95-GHz harmonically mode-locked semiconductor laser is measured to be 13.4 mW at 600 mA.     

Tunable infrared generation using a femtosecond 250 kHz Ti:sapphireregenerative amplifier

A mode-locked Ti:sapphire regenerative amplifier system pumped with a single argon ion laser produces μJ energy 100 femtosecond pulses of 800 nm wavelength at 250 kHz repetition rate. Pumping a Type II BaB₂O₄ (BBO) optical parametric amplifiers (OPA) with this output generates 500 nJ infrared pulses and continuous tuning from 1.1 μm to beyond 2.5 μm. Difference frequency generation of the signal idler output from this OPA source in AgGaS₂ produces 60 nJ mid infrared pulses and continuous tuning from 2.4 μm to beyond 12 μm     

A scheme of picosecond pulse shaping using gain saturationcharacteristics of semiconductor laser amplifiers

To obtain high power, well shaped picosecond pulses from gain-switched semiconductor lasers, the use of dynamic gain saturation characteristics of semiconductor laser amplifiers was investigated theoretically and experimentally. A configuration of a reflected-wave amplifier (RWA) with single-side external coupling is introduced for pulse shaping, which is found to be suitable for enhancing dynamic gain saturation. By a combination of a distributed feedback laser oscillator at 1.3 μm in wavelength and a reflected-wave amplifier of 400 μm cavity length with asymmetric facet reflectivities of 0.01% and 30%, single-mode optical pulses with almost no tailing, full width at half maximum of 15 ps, and peak power exceeding 50 mW were obtained without pulse broadening, despite the considerable tail structure of the incident pulse     

All-Fiber Picosecond Laser System at 1.5 $mu$m Based on Amplification in Short and Heavily Doped Phosphate-Glass Fiber

Amplification of ultrashort pulses in doped fibers is limited by an onset of nonlinear effects in the fiber. At the 1.5-mum wavelength, single-mode fibers typically have anomalous dispersion. The self-phase modulation combined with dispersion leads to instability of multinanojoule pulses in such fibers. Various techniques developed to amplify pulses beyond the nonlinearity limit typically rely on a delicate balance between dispersive and nonlinear effects in different parts of the laser system. We report a simple all-fiber alternative to these complex techniques that utilizes a rapid amplification of pulses in a short and heavily doped phosphate-glass active fiber. In our preliminary experiments, picosecond pulses at 1.5 mum generated by a passively mode-locked fiber oscillator at a repetition rate of 70 MHz are amplified in a 15-cm-long heavily Er-Yb codoped fiber amplifier to the average output power of 1.425 W. The pulse energy and peak power reach 20.4 nJ and 16.6 kW, respectively, while the pulse distortion is minimal in both temporal and spectral domains. Further power up-scaling is possible by using active phosphate fiber with a large mode area, in the amplifier stage     

An 8.2 J phase-conjugate solid-state laser coherently combiningeight parallel amplifiers

We describe a phase-conjugate master oscillator-power amplifier configuration in which as many as eight parallel flashlamp-pumped Cr:Nd:GSGG amplifiers and four parallel CD*A frequency doubling crystals were coherently combined. Operating at a pulse repetition frequency of 1.25 Hz, we demonstrated an output energy of 8.2 J at 1 μm and 4.4 J at 530 nm for a 54% frequency-doubling efficiency. This effort represents the highest reported output energy achieved using coherent coupling via phase conjugation. In subsequent experiments at a pulse repetition frequency of 5 Hz, we produced ~22 W of 1.06 μm average power with a beam quality that was ~2.5 times diffraction-limited. The observed far-field intensity profile indicates that we achieved effective and consistent compensation of optical-path length differences among the multiple parallel amplifiers and frequency-doubling crystals     

MOPA方式高峰值功率脉冲光纤放大器模拟

为了研究如何从脉冲种子光经放大器后获得能量为毫焦级、纳秒级脉宽的激光脉冲,以及重频、受激喇曼效应对输出激光脉冲的影响,采用基于主振荡动率放大方式建立了3级脉冲双包层掺Yb光纤放大器的瞬态理论模型。在不同重频下对能量为10nJ、脉宽为100ns的脉冲种子光经放大后的脉冲能量、峰值功率、平均功率、脉宽及受激喇曼效应进行了数值模拟。计算数据表明,当重频小于200Hz时输出激光脉冲的能量、波形受重频的影响很小,可以忽略不计,在适当参量下受激喇曼效应对各级放大输出几乎没有影响。结果表明,适当选择3级光纤放大器的各项参量可以实现毫焦级的激光脉冲输出。     

Generation of transform-limited optical pulses using a combinationof a gain-switched diode laser and a semiconductor opticalamplifier

We introduce a novel method for generating nearly transform-limited picosecond optical pulses at multi-gigahertz repetition rates. Frequency-chirped optical pulses are first produced using a gain-switched semiconductor diode laser, and they are subsequently amplified by a semiconductor optical amplifier. The red frequency chirp in the gain-switched pulses is compensated for almost completely as a result of gain-saturation-induced self-phase modulation occurring in the amplification process. Experimentally, we have successfully generated nearly transform-limited 28-ps optical pulses at a 5-GHz repetition rate using a distributed feedback diode laser and a traveling wave semiconductor optical amplifier     

160 W激光二极管抽运电光调Q主振荡功率放大器绿光激光器

介绍了激光二极管抽运的高重复频率、大能量绿光固体激光器研制成果。激光器采用电一光调Q，主振荡功率放大器（MOPA）结构。根据放大器的设计要求，研制了抽运功率达12kW，占空比为15％的激光二极管侧抽运Nd：YAG棒状激光模块。在重复频率500Hz，脉冲宽度15ns条件下，实现了单脉冲能量1．27J的1064nm输出，光束质量β小于2．5。采用Ⅱ类相位匹配KTP晶体外腔倍频，在基频能量1J，重复频率400Hz，抽运功率密度67MW／cm^2时，获得大于405mJ的绿光输出（平均功率达160W），倍频效率约为40％，绿光光束质量β〈5。     

Ultralong dispersion-shifted erbium-doped fiber amplifier and itsapplication to soliton transmission

Distributed, dispersion-shifted erbium-doped fiber amplifiers with doping concentrations as low as 0.1-0.5 p.p.m. (0.1-0.5×10^-4 wt.%) were fabricated and their grain characteristics studied for the purpose of soliton amplification. A 9.4-km dual-shape-core-type amplifier with a 0.5-p.p.m. concentration had a gain of more than 20 dB at 1.535 μm and 10 dB at 1.552 μm with a forward pumping configuration, and it could successfully amplify and transmit a 20-ps soliton pulse train at a 2.5-GHz repetition rate. The soliton transmission characteristics of an 18.2 km long fiber amplifier were studied using backward and forward pumping. It was found that A=1.5 soliton pulses with a pulse width of 20 ps could be amplified over 18.2 km at a repetition rate of 5 GHz, where soliton narrowing to 16 ps was observed     

基于微结构光纤的光纤环激光器

报道了一种基于微结构光纤(MF)的光纤环激光器.通过微调控制信号的频率,激光器实现了稳定的锁模状态,在C波段获得了重复频率为10 GHz、宽度小于8ps的相干光脉冲输出.在该激光器中,采用了掺Er光纤放大器(EDFA)作为腔内增益介质,并使用了25 m长、具有反常色散和高非线性的MF作为脉冲压缩介质.通过调整腔内的带通滤波器中心频率可以实现对工作波长的连续调谐,因此该激光器可作为波分复用(WDM)系统的可调谐光源.     

High-intensity terahertz pulses at 1-kHz repetition rate

We report the generation of terahertz pulses with 0.4-μJ pulse energy at 1-kHz repetition rate using a large-aperture GaAs photoconductor with 3-cm gap aluminum electrodes, biased at voltages up to 45 kV. The terahertz output energy saturates at a laser fluence of 40 μJ/cm² at low-bias fields, while no clear saturation point was observed at high-bias fields. The output was found to be dependent on the repetition rate: at high fluences, pulse energy at 1 kHz is higher than that at 100 Hz by as much as 60%. A study of the behavior of the terahertz pulse energy and pulsewidth as a function of the pulsewidth of the laser excitation was conducted and compared with theoretical predictions. Propagation properties of the terahertz beam were also characterized, leading to a focal spot size as small as 800 μm at the focus of a 2.5-in focal length parabolic mirror     

Tunable ultraviolet generation using a femtosecond 250 kHzTi:sapphire regenerative amplifier

A mode-locked Ti:sapphire regenerative amplifier system pumped with a single argon ion laser produces μJ energy femtosecond pulses of 800 nn wavelength at up to 300 kHz repetition rate. This output is used to generate tunable femtosecond pulses in the ultraviolet to as short as 240 mn by using a combination of harmonic generation, white-light continuum generation and parametric amplification. A variety of techniques to access different parts of the UV spectrum are presented     

25kHz、约2ns声光调Q Nd:YVO4激光器研究

为了获得高重频窄脉冲高光束质量激光输出,采用LD抽运Nd:YVO₄晶体声光调Q方案,进行了相关理论分析和实验验证,振荡级获得了重频25kHz、单脉冲能量22.4μJ、脉冲宽度2.19ns、光束质量因子M2 < 1.2的种子激光,光光转换效率为24.3%;放大级获得了重频25kHz、单脉冲能量585μJ、脉冲宽度2.26ns、光束质量因子M2 < 1.7的激光输出,提取效率为15.6%。结果表明,采用LD抽运Nd:YVO₄晶体声光调Q方案能够获得高重频、窄脉冲、高光束质量激光输出,其实验现象与理论计算结果较为符合。     

Broad-band diode-pumped ytterbium-doped fiber amplifier with 34-dBmoutput power

We investigate a high-power diode-pumped double-clad ytterbium-doped fiber amplifier with 34-dBm average output power and 1050-1095-nm bandwidth. A multidiode concentrator pumps the amplifier at 980 nm, with ~6 W of power launched into the inner cladding. Besides CW-signals, we amplify pulses from a mode-locked laser to 1 kW of peak power with only minor nonlinear distortions as well as pulses from a Q-switched laser to 50 μJ of energy. Reflections and backscatter limit the gain of the amplifier to 40 dB for a pump power of 2.5 W. For higher pump-powers than this, the amplifier started to self-Q-switch. The results are important for the development of cladding-pumped high-power fiber amplifiers     

Simultaneous compression and amplification of ultrashort pulses atMHz repetition rates

The authors report simultaneous compression and chirped pulse amplification at megahertz repetition rates of ultrashort pulses using a cavity-dumped dye laser with a pumping argon ion laser as the amplifier. In a single stage, the pulse is compressed by a factor of 25 and the energy per pulse is simultaneously increased by a factor of 2, without reducing the repetition rate. Starting with a pulse that has a duration of 4.3 ps and a peak power of 5.8 kW, a pulse with a duration of 170 fs and a peak power of 294 kW is obtained. A second stage of pulse compression is used to obtain a broadband pulse with a duration >~50 fs and a peak power of ~100 kW at 2 MHz