新型钒酸盐混晶Nd∶Gd_(0.42)Y_(0.58)VO_4/Cr~(4+)∶YAG被动调Q锁模特性研究

研究了Nd∶Gd0.42Y0.58VO4混晶的激光运转特性。采用Cr4+∶YAG晶体作为被动可饱和吸收体,实现了Nd∶Gd0.42Y0.58VO4混晶的调Q锁模激光运转。实验测量了不同Cr4+∶YAG初始透过率情况下激光器的输出特性。在Cr4+∶YAG初始透过率T0=86.3%,输出镜透过率T=10%时,调Q锁模运转阈值为2.8 W,随着抽运功率的增加,调制深度逐渐加大。采用透过率T=20%的输出镜,注入抽运功率10.3 W时,调Q锁模深度约为70%,相应的脉冲包络重复频率为40 kHz,半高宽度为25 ns,平均输出功率为2.58 W,光-光转换效率为25%。     

高平均功率高重复率固态双Nd:YVO4基模激光器

报道了采用国产大功率光纤束模块双端泵浦双Nd：YVO4激光晶体和声光调Q技术,实现了高平均功率、高重复频率的1064nm激光输出。通过降低Nd：YVO4激光晶体的掺杂浓度,采用双端泵浦双晶体,在晶体热效应允许的范围内最大限度地利用了泵浦光的能量,通过腔内插入声光调Q器件,在晶体注入总功率为50W的情况下,得到了24W的TEM00模连续波1064nm激光输出。最高重复频率为50kHz时,平均输出功率为22．9W,脉冲宽度为38ns,相应的光-光转换效率为45．8％;在重复频率为10kHz时,具有最大单脉冲能量1．55mJ,相应的脉冲宽度为15ns,峰值功率达到了103kW。     

Passive Q-switching in all-fibre Raman laser with distributed Rayleigh feedback

The experimental demonstration of the all-fibre passive Q-switching operation of a Raman fibre laser is reported. Giant pulses around 1550 nm with a peak power of 1 kW and pulse duration down to 1 ns were obtained with a 10 km-long fibre cavity pumped by a 2.4 W continuous-wave fibre laser source. Reported experimental data indicate that Rayleigh, Brillouin and Raman scatterings are all involved in the pulse generation process.     

High-peak-power picosecond optical pulse generation from Q-switched bow-tie laser with a tapered traveling wave amplifier

Picosecond optical pulse amplification along with spatial mode filtering has been demonstrated, using a tapered traveling wave semiconductor post-amplifier and multicontact Q-switched bow-tie laser. Optical pulses of 13 ps duration were generated with a single-lobed, near diffraction-limited radiation pattern. Peak powers of 44.7 W, and pulse energies as high as 0.58 nJ were observed.     

Mode-locked operation of a master oscillator power amplifier

We report the first mode-locked operation of a tapered amplifier MOPA to generate short optical pulses with record high average powers and pulse energies. The MOPA is constructed using a discrete semiconductor oscillator and amplifier operating at 940 mm wavelength. Pulses of 4.2 ps duration are generated with average powers of 296 mW and peak powers of 28.1 W. The energy of these pulses was 118 pJ, corresponding to energies more than an order magnitude greater than the gain saturation energy in the mode-locked laser itself, and also corresponds to energies internal in the amplifier in excess of the gain saturation energy. Although the amplifier saturation energy limits the pulse energy obtainable in a mode-locked laser, the MOPA configuration demonstrates that generation of pulses with energies in excess of the amplifier saturation energy is feasible in a post-amplification stage     

Microwave Nanosecond Pulse Burnout Properties of GaAs MESFET's

Microwave nanosecond pulse burnout data have been measured at 9.3 GHz for three commercially available 1-mu m gate MESFET's. Values for the incident pulse power required to cause burnout are concentrated in the ranges 4-10 W for 10-ns pulses, 12-25 W for 3-ns pulses, and 15-30 W for 1.5-ns pulses. The corresponding values for the absorbed microwave pulse energy required to cause burnout are concentrated in the ranges 0.3 to 0.6 ergs for 10-ns pulses, 0.2-0.4 ergs for 3-ns pulses, and 0.2-0.35 ergs for 1.5-ns pulses. Two dominant failure modes in overstresed MESFET's have been observed. One is a gate-to-source low-resistance path (5-25 Omega) which frequently is correlated with metal migration (mainly gold) from the source metallization to the gate metallization. This failure mode was dominant when MESFET's failed at lower power Ievels as at 10 ns. The other dominant failure mode is a reduction in I/sub DSS/ or a drain-to-source short which is correlated with massive damage in the channel region between the source and gate metallizations. This failure mode was dominant when MESFET's failed at high power levels as at 1.5 ns.     

LD光纤耦合端面泵浦Nd:YVO4/Cr4+:YAG激光器

根据Siegman的被动调Q判据,Nd:YVO4晶体由于受激发射截面大、上能级寿命短,很难获得被动调Q输出。利用LD光纤耦合端面泵浦Nd:YVO4晶体,在泵浦功率3.5W时,连续运转获得最大输出1.4W,相应的光光转换效率为40%,同时采用Cr4+:YAG可饱和吸收体,成功地实现了Nd:YVO4被动调Q运转,获得了脉宽11.7ns,重复频率22kHz调Q输出。     

Coherent pulsed injection seeding of two gain-switchedsemiconductor lasers

High-power, narrow-spectrum, short pulses at a wavelength near 830 nm are needed for optical logic applications. The authors report the generation of two coherent trains of pulses by pulsed injection seeding of two gain-switched semiconductor lasers with one mode-locked master oscillator. The available power was doubled and both lasers emit in nearly identical spectral lines. Short pulses (30-50 ps) are generated at a repetition rate of 1.9 GHz. The spectrum is reduced to a single mode cluster and shows a 1.7 Å wide chirp suitable for pulse compression. The peak power is 0.1 W for each pulse train. The capability of this technique for coherent power combining is demonstrated     

基于SOA、SMF和NOLM的光脉冲压缩研究

建立了基于半导体光放大器、单模光纤和非线性光纤环行镜组成的光脉冲压缩的设计模型,通过数值模拟的方法对该模型进行了研究,其结果表明:对峰值功率为10mW、半峰全宽为33.3 ps的高斯脉冲经此方案压缩后,可以获得峰值功率为25 W以上,半峰全宽为170 fs左右且几乎无基座的超短脉冲.     

Picosecond pulse generation in optically pumped, ultrashort-cavity, InGaAsP, InP, and InGaAs film lasers

Ultrashort-cavity semiconductor film lasers made with InP, InGaAsP, and InGaAs have generated picosecond pulses over the wavelength range from 0.77 μm to 1.65 μm after optical pumping by an intense, 0.5 ps pulse at 0.625 μm. Each material composition operates over an energy range from just below the bandgap to more than 20 percent above the bandgap. For a given composition, pulse duration increases as wavelength increases; for different compositions, pulse durations increase as the bandgap energy decreases. Pulse durations range from 1.4 ps (for InP) to about 30 ps. Peak power is in the range of 1- 10 W. These unique properties of ultrashort-cavity film lasers are due to the combination of bandfilling caused by the intense photoexcitation and the ultrashort cavity, which provides widely spaced resonances to ensure single mode operation and also produces a short photon lifetime necessary for optical gain switching. The film lasers have a uniform, nearly Gaussian, spatial mode.     

2 ns pulse width high repetition rate short cavity acousto-optically Q-switched Nd:YVO/sub 4/ laser

With a specially constructed miniature acousto-optical Q-switch, 2 ns pulses with 10.3 muJ energy and 5.13 kW peak power at 80 kHz repetition rate were obtained in an end pumped short cavity acousto-optically Q-switched Nd:YVO₄ laser. This is believed to be the shortest pulse width obtained in a solid-state laser by acousto-optical Q-switching. At 500 kHz repetition rate, 10 ns pulses were generated     

Reducing pulse durations in diode pumped Q-switched solid-state lasers

The authors describe a subminiature, laser-diode-pumped, acoustooptic Q-switched Nd:YLF laser. The laser utilizes a very short cavity and laser crystal cooling to increase gain and reduce pulse width. Exploiting this technology results in 1.321 mu m pulses with durations and peak powers of 4.7 ns and 1100 W at 2 kHz and 8.7 ns and 250 W at 10 kHz in Nd:YLF. Similarly, 10 kHz pulses at 1.047 mu m have 2.7 ns duration and 1500 W peak power, also in Nd:YLF.<>     

二极管激光侧面泵浦Nd：YAG的色心调Q激光器

报道准连续６０Ｗ线列阵二极管激光器侧面泵浦的Ｎｄ：ＹＡＧ激光器及用ＬｉＦ：Ｆ２－晶体作饱和吸收体的被动调Ｑ激光器。在重复频率为１０Ｈｚ，泵浦脉宽为４００μｓ，峰值功率为６０Ｗ的泵浦速率下，激光弛豫振荡每周期输出的能量为３ｍＪ，相应的全光光效率为１２．５％。在调Ｑ方式下运转时，每周期可得到３个能量为４００μＪ，脉宽为１１．５ｎｓ的脉冲。通过腔结构的调整，实验中还获得能量为２００μＪ的单横模的单脉冲输出。通过数值模拟讨论了脉冲的形成过程和脉冲特性，并对进一步的研究工作提出了改进方案。     

低温生长GaAs实现半导体泵浦红外激光器被动调Q锁模研究

用低温生长GaAs红外晶体材料作为饱和吸收体兼输出镜,在二极管泵浦全固态激光器上实现了调Q锁模。激光器调Q运转阈值为2W。当注入泵浦功率为3．6W时,调Q锁模开始出现。当注入泵浦功率为8．4W时,平均输出功率达到837mW,调Q包络的重复频率为100kHz,锁模脉冲的重复频率为760MHz。     

Synchronous amplification of subpicosecond pulses

In high-gain dye amplifiers, the effective storage time of the gain medium is only a few hundred picoseconds. Therefore, efficient amplification of ultrashort pulses places a stringent requirement on the synchronization between the pump pulse and the pulse to be amplified. We present a technique of short pulse generation using a dye laser synchronously pumped by a frequency-doubled CW mode locked Nd:YAG laser. Pulses as short as 70 fs are produced. The short optical pulses are subsequently amplified with two different synchronous amplification schemes using 100 ps pulses to establish the gain in the dye amplifier stages. Subpicosecond pulses with energies from a few hundred nanojoules at 500 Hz to a few hundred microjoules at 7 Hz can be obtained.     

Limitations imposed by stimulated Raman scattering of 1550 nmhigh-energy pulse transmission

The limitations imposed by stimulated Raman scattering on 1550 nm high-energy pulse transmission in single-mode optical fiber are investigated. The generation of a Stokes pulse from an input pulse with peak power up to 60 W and duration on the order of 10 ns is experimentally studied and numerically simulated. This is the first demonstration of Stokes pulse generation in optical fiber from pump pulses within the 1550 nm telecommunications window. Experiment and theory show that there is an optimum input power for a given pulse duration and distance that maximizes the energy transmitted over long fibers     

光纤饱和吸收体掺镱全光纤化激光器

报道了一种基于光纤饱和吸收体的掺镱全光纤调Q激光器,为了获得较高峰值功率较窄脉宽的激光脉冲输出,利用掺镱光纤的可饱和吸收效应,以20/130 μm规格的大模场双包层掺镱光纤作为增益光纤,以10/130 μm规格的单模双包层掺镱光纤作为可饱和吸收体来实现被动调Q。该激光器采用全光纤化的结构,结构紧凑,以较低的成本获得了较为高效的脉冲输出。最终获得了平均功率最高为3 W,直线效率约为30%,重复频率为10~100 kHz可调,脉宽最窄为344 ns,光谱宽度为0.05 nm、中心波长为1 064 nm的激光输出。     

FROG measured high-power 185-fs pulses generated by down-chirping of the dispersion-managed breathing-mode semiconductor mode-locked laser

A dispersion-managed breathing-mode mode-locked semiconductor ring laser generates linear down-chirped pulses which are dispersion compensated to duration as short as 185 fs and characterized by second-harmonic generation frequency-resolved optical gating. Down-chirping when compared to up-chirping allows broader mode-locked spectra and shorter pulse generation owing to the temporal and spectral semiconductor gain dynamics. The measured average output power is 14 mW at 323-MHz pulse repetition rate, implying a peak power of /spl sim/230 W, and a focused intensity of /spl sim/4.6 GW/cm/sup 2/. To our knowledge, this is the highest peak power and the shortest pulse generation from an electrically pumped all-semiconductor system, obtained only by linear chirp compensation.     

Pulse extraction and kW peak power generation with the nonlinearoptical loop mirror in an erbium-doped fiber amplifier chain

The nonlinear optical loop mirror is used to suppress optical noise and residual coherent background between repetitive short optical pulses. An input pulse power fraction of only 0.6% is improved to 80% at the output of the device. The device is passive and, in principle, independent of wavelength, pulse width, pulse repetition rate, and input signal polarization. This technique can be used to generate high peak power pulses using a cascade of optical amplifiers. Here we report the generation of 140 ps square pulses with 2 kW peak power (0.3 μJ) at a repetition rate of 10 kHz     

Mode-Locked Bi-Doped All-Fiber Laser With Chirped Fiber Bragg Grating

We demonstrate a bi-doped fiber laser with dispersion compensation provided by a linearly chirped fiber Bragg grating. Reliable self-starting mode-locking was achieved by using an InGaAsN semiconductor saturable absorber mirror. The all-fiber laser generated short optical pulses with a duration of 1.9 ps at ~ 1165 nm. The large anomalous dispersion of the fiber grating ensured operation in the soliton pulse regime. This in turn enabled us to increase the repetition rate of the output pulse train up to 100.6 MHz via harmonic mode-locking.