1064nm激光诱导等离子体开关控制355nm脉宽可调输出

为得到脉宽可控的355nm紫外脉冲激光输出,采用1064nm脉冲激光诱导等离子体开关技术,控制355nm激光脉冲宽度,在激光电离Cu小孔内壁表面及空气击穿共同作用下,获得了2.8ns～10ns的脉宽可调输出.讨论了1064nm单脉冲输出能量对脉宽压缩的影响,在无延时情况下得到了脉宽最短达2.8ns的脉冲激光输出.在此基础上,保持1064nm单脉冲输出能量不变,采用延时装置改变两光路间的光程差,以控制等离子体开关相对于355nm激光脉冲的形成时间,最终得到脉宽可调的脉冲激光输出.结果表明,等离子体开关结构简单、操作方便、适用范围广,是一种较好的脉冲整形手段.     

Nd:YVO4自锁模皮秒激光器

设计并研究了Nd:YVO4自锁模皮秒激光器,探究了激光器的最佳锁模条件。观察并分析了自锁模皮秒激光器准周期锁模、倍周期锁模状态,研究并测量了结构紧凑的直腔自锁模激光器的输出特性。谐振腔为凹平直腔,Nd:YVO4晶体作为激光增益介质和克尔介质,在未加其他锁模元件的情况下,实现了1 064 nm高效率连续锁模脉冲激光输出。晶体距输入镜16 mm、腔长为90 mm时,对1 064 nm透过率分别为10%、20%、30%和50%的四种输出镜下激光器的输出特性进行了对比分析。对激光器进行优化设计,输出镜透过率为10%,泵浦功率为8 W时,激光器输出功率为2.76 W,斜效率高达43.2%,锁模脉冲重复频率为1.43 GHz,激光器实现了高效、稳定的连续锁模。     

Mode-Locking in a Semiconductor Fiber Laser Using Cross-Absorption Modulation in an Electroabsorption Modulator and Application to All-Optical Clock Recovery

We demonstrate the use of cross-absorption modulation in an electroabsorption modulator to actively mode-lock a semiconductor fiber laser at 10 GHz. The laser cavity also comprises a linearly chirped fiber Bragg grating to obtain wavelength tunable operation based on the dispersion tuning approach. The laser exhibits uniform output pulse characteristics throughout the tuning range. We also investigate the impact of using different types of optical pump signals on the output pulses. Finally, we demonstrate the application of the mode-locked laser for all-optical clock recovery.     

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     

1064nm激光诱导等离子体开关控制355nm脉宽可调输出

为得到脉宽可控的355nm紫外脉冲激光输出,采用1064nm脉冲激光诱导等离子体开关技术,控制355nm激光脉冲宽度,在激光电离Cu小孔内壁表面及空气击穿共同作用下,获得了2.8ns～10ns的脉宽可调输出。讨论了1064nm单脉冲输出能量对脉宽压缩的影响,在无延时情况下得到了脉宽最短达2.8ns的脉冲激光输出。在此基础上,保持1064nm单脉冲输出能量不变,采用延时装置改变两光路间的光程差,以控制等离子体开关相对于355nm激光脉冲的形成时间,最终得到脉宽可调的脉冲激光输出。结果表明,等离子体开关结构简单、操作方便、适用范围广,是一种较好的脉冲整形手段。     

Voltage–frequency converter for laser welding control

An experimental model of a voltage–frequency converter was realised and utilised for the control of the thermal behaviour by the laser welding of thermoplastic polymer materials. The input signal of 0–10?V comes from a thermal–optical real-time analysing device of the welding process. The output signal of 0–300?Hz is introduced to the input interface of a laser welding equipment, for setting the laser pulse frequency. Operation tests were performed on the laser welding equipment type HL 124P LCU. The pulses have rectangular waveform, with the amplitude of 20?V. The frequency is very stable, with deviations of less than 0.5?Hz. The waveform and the frequency response at the converter output are appropriate.     

Performance improvements in high-frequency modulation of a laser diode under enhanced optical feedback

Improvement in the high-frequency modulation characteristics of a Fabry-Perot laser diode has been observed when the device is driven in an external cavity that provides an amplified optical feedback. At a driving frequency of 10 GHz, the weak sinusoidal waveform in the original output is turned into a train of narrow pulses with a width of 23 ps. Under an optimized feedback level, an improvement of 15.4 dB in the electrical modulation efficiency and 21.2 dB in the sidemode suppression ratio are observed. The output pulses also exhibit a reduced chirp with a minimized total root-mean square noise.     

Generation and detection of high-speed pulses of mid-infraredradiation with intersubband semiconductor lasers and detectors

Semiconductor lasers and detectors based on intersubband electron transitions are used to generate and measure high-speed pulses of mid-infrared radiation. In particular, we use a commercial comb generator to gain-switch a state-of-the-art 8-μm quantum cascade laser mounted in a high-speed package. The output pulses of this device are then detected with a small-area quantum-well infrared photodetector, also packaged for high-speed operation. Pulse widths shorter than 90 ps are directly measured with this system. Accounting for the finite response time of the detection electronics, a deconvolved duration of approximately 45 ps is extrapolated     

Axisymmetric angular encoder for laser fusion

We report the demonstration of an angular encoder which produces a discrete conical scan of 25 pulses, each 10 ns in duration. The device is a key optical subsystem for efficient generation of short optical pulses from laser media with short energy storage times. In particular, an encoder of this type may be necessary for use of the rare gas halide laser media in fusion experiments. Our device was also operated as a ring resonator with internal imaging and image rotation. Potential uses, aside from laser fusion, include laser scanning systems and resonator designs in which image rotation is desirable.     

Synchronized transform-limited operation of 10-GHz colliding pulse mode-locked laser

We report a 10-GHz colliding pulse mode-locked laser fabricated with integrated active-passive waveguides. The laser fabrication adopted a deep reactive ion etching and single-step metal-organic vapor phase epitaxy regrowth process for forming the buried heterostructure waveguide. Clean output pulses resulted from laterally tilting the active-passive interface and effectively suppressing residual back-reflections at the interface. Hybrid mode-locking resulted in a synchronized transform-limited sech/sup 2/optical waveform. Pulsewidth, chirp, timing jitter, and frequency-locking range were investigated through systematic device biasing condition optimization.     

Simultaneous determination of the spectral and temporal properties of tunable, single, picosecond pulses from a short cavity dye laser

We report simultaneous quantitative spectral and temporal measurements of the output pulses from a single-axial mode rhodamine 6G short cavity (1-8 mum) dye laser. The dye laser was pumped at 10 Hz with single second harmonic (532 nm) pulses from a mode-locked Nd⁺³:YAG laser. Spectral measurements made with a high resolution spectrograph and temporal measurements made with an ultrafast streak camera indicate the production of Fourier transform limited pulses for near threshold operation. Output pulses of 7-14 ps (FWHM) are observed from the short cavity dye laser when pumped with 15-30 ps duration 532 nm pulses. The output pulse delay and jitter are also investigated. A theoretical model for the temporal evolution of the pulses is presented and compared with the experimental results.     

自调Q掺铒光纤激光器动态特性研究

为了研究自调Q掺铒光纤激光器输出动态特性,采用搭建全光纤结构的线形腔和环形腔自调Q掺铒光纤激光器进行了理论分析和实验验证。实验中,当抽运功率达到起振阈值后,随着抽运功率的增加,用示波器观察输出激光,线形腔输出激光依次经历了连续波、自调Q两种运行状态,由于抽运功率的限制,未能再次出现连续波运行状态,而环形腔输出激光则先经历了自调Q运行状态,然后是连续波运行状态;线形腔在抽运功率21mW~190mW的范围内,可获得脉冲宽度8s ~100s范围内可调、重复频率2.5kHz~54kHz范围内可调的自调Q脉冲;环形腔在抽运功率为16.2mW~110mW时,可获得的脉冲宽度在165s左右。结果表明,自调Q掺铒光纤激光器因腔结构的不同,输出激光动态特性也不同;线形腔和环形腔均有自调Q脉冲输出,但线形腔自调Q范围更大。     

A high repetition rate ion laser spanning the 195-225 nm spectral region

This paper describes the construction and operation of a water-cooled noble gas ion laser which generates average powers of the order of a milliwatt at 5 strong transitions between 195 and 225 nm. This pulsed laser has been operated at repetition rates up to 200 Hz and has produced average powers up to 5.1 mW at 219.2 nm. The pressure and voltage dependence of output power, along with preionization effects, gain, saturation intensities, and the effects of discharge current pulse length are discussed. The optical pulses can be precisely synchronized with respect to an electrical reference signal, and the laser operates at all wavelengths with Brewster windows, permitting convenient interchanging of resonator mirrors. This device has been designed for use as an ultraviolet illuminator in a photoelectron microscope.     

20 GHz optical waveguide sampler

Picosecond pulses have been produced from the CW output of a He-Ne laser using a microwave-modulated optical waveguide interferometer formed in Ti-indiffused LiNbO3. An experimental frequency spectrum demonstrating 97 percent modulation is presented along with theoretical predictions for the spectral components of signals produced by both ideal nonideal devices. A device modulated with 1 W of power at 10 GHz exhibited a spectrum corresponding to a train of 19 ps FWHM pulses produced at a repetition rate of 20 GHz. Applications of the device in signal processing operations utilizing sampling and demultiplexing schemes are discussed.     

10-GHz train of sub-500-fs optical soliton-like pulses from a surface-emitting semiconductor laser

We report sub-500-fs operation of a passively mode-locked diode-pumped external-cavity surface-emitting semiconductor laser at a repetition rate of 10.014 GHz. For an incident pump power of 706 mW, the laser produced 486-fs soliton-like pulses, with an average output power of 30.3 mW. The role of the ac Stark effect in shaping subpicosecond pulses is demonstrated.     

Single-frequency Ti:Al2O3 ring laser

Over 500 mW of single-frequency power has been obtained from a Ti:Al₂O₃ ring laser pumped by 10 W (all lines) from an argon ion laser. The ring laser can be tuned from 750 to 850 nm while maintaining more than 100 mW in single-frequency operation without realignment or a change of optics. The free-running frequency stability of the laser is 3 MHz. Thermal effects cause changes in the ring cavity parameters, limiting the output power. This ring laser has also been operated with an acoustooptic mode locker to obtain 200-ps mode-locked pulses at 250 MHz with nearly the same average power as in single-mode operation     

Q-switching cleaved-coupled-cavity laser with an integrated intracavity modulator

We describe fabrication and performance of a Q-switching cleaved-coupled-cavity laser with an integrated intracavity modulator. The pulse repetition frequency of this 3-section device was tunable between 320 and 450 MHz with an external microwave injected signal, the modulation depth of the pulsations was 80?100% with a nearly single-longitudinal-mode output spectrum, and the Q-switched light pulses were modulated by a pseudorandom PCM signal at 322 Mbit/s.     

小型化轴流式非链式脉冲氟化氘激光器

采用轴流循环流动方式更新非链式脉冲氟化氘（DF）激光器工作介质，搭建了一台小型化自引发放电DF激光器实验装置，开展了轴流DF激光器输出性能实验研究。单脉冲工作时，在工作气体配比SF₆∶D₂=10∶1，总气压8 kPa时，实现单脉冲能量800 mJ激光输出，全波半高宽约120 ns，其性能与横流放电非链式脉冲DF激光器相似。重复频率放电时，实现了DF激光器重复频率20 Hz稳定运转，得到的最大输出功率为13.1 W，重频脉冲幅值差优于±5%，并展望了轴流式DF激光器高重频工作的前景。文中提出的轴流式非链式脉冲DF激光器为小型化、工程化中红外光源提供了新的技术途径。     

Color center lasers passively mode locked by quantum wells

Using multiple-quantum-well (MQW) saturable absorbers, a NaCl color center was passively mode locked to produce 275-fs transform-limited, pedestal-free pulses with a peak power as high as 3.7 kW. The pulses are tunable from λ=1.59 to 1.7 μm by choosing MQWs with different bandgaps. The output pulses from the laser were shortened to 25 fs using the technique of soliton compression in a fiber. The steady-state operation of the laser requires the combination of a fast saturable absorber and gain saturation     

Multipulse operation of a high average power, good beam qualityzig-zag dye laser

A laser pumped zig-zag dye laser operating at 568 nm with a pulse length ~2 μs has been sealed to high power using a MOPA configuration. Pulse energies in excess of 7 J with beam quality <2 XDL have been achieved under repetitively pulsed, 10 Hz operation. RMS jitter was measured as 0.12 of a 1 XDL spot. The device has operated with over 70 W output for runs up to 5 s. Substantially longer run times and output powers are possible. This device represents an advance in dye laser capabilities. Improvement in pointing accuracy of better than an order of magnitude have been demonstrated. In addition, an improvement in beam quality by about an order of magnitude has been achieved compared to other dye lasers operating in this power range