高峰值功率重频脉冲固体激光器

综述了高峰值功率重频脉冲固体激光器的发展现状，对其中的Ｑ开关、腔倒空、锁模等窄脉冲技术和放大技术进行了分析，展示了高峰值功率重频脉冲固体激光器的发展前景。     

High repetition rate collisional soft X-ray lasers based on grazing incidence pumping

We discuss the demonstration of gain-saturated high repetition rate table-top soft X-ray lasers producing microwatt average powers at wavelengths ranging from 13.9 to 33 nm. The results were obtained heating a precreated plasma with a picosecond optical laser pulse impinging at grazing incidence onto a precreated plasma. This pumping geometry increases the energy deposition efficiency of the pump beam into the gain region, making it possible to saturate soft X-ray lasers in this wavelength range with a short pulse pump energy of only 1 J at 800-nm wavelength. Results corresponding to 5-Hz repetition rate operation of gain-saturated 14.7-nm Ni-like Pd and 32.6-nm line Ne-like Ti lasers pumped by a table-top Ti:sapphire laser are reported. We also discuss results obtained using a 1 /spl omega/1054-nm prepulse and 2 /spl omega/527-nm short pulse from a Nd:glass pump laser. This work demonstrates the feasibility of producing compact high average power soft X-ray lasers for applications.     

High repetition rate LC oscillator

LC oscillators have been built which can produce multikilowatt RF pulses in the megahertz frequency range with repetition rates of tens of kilohertz. The L and C for these oscillators can be determined from the frequency requirement and the high-Q requirements. The high repetition rates are achieved using a high-pressure spark-gap switch together with a dc to ac inverter power supply. Closely spaced antenna elements can be used to increase the number of cycles in the radiated waveforms (radiated Q).     

High repetition rate pulsed gas lasers and their applications in chemistry and isotope separation

Presented in this paper are the results of experimental studies of pulsed high repetition rate XeCl, CO2, NH3, and CF4lasers with a closed gas cycle. Some applications of these lasers in chemistry and isotope separation are discussed.     

Electrically steerable lasers using wide-aperture VCSELs

A wide-aperture vertical-cavity surface-emitting laser has been fabricated so as to enhance the transverse mode selection. It was found that the far field emission can be made to exhibit two distinct steerable beams. The laser beams may be steered from 30° away from the normal right up to normal emission by varying the driving current. The steering effect is a thermal effect as confirmed by transient waveform analysis. A two-channel switch was built with switching time between channels of 10 μs and crosstalk of greater than 18 dB     

High repetition rate CH4 laser

A 16-μm CF₄ laser oscillator has operated at 1 kHz in a cooled static cell. Pump energies required from the low pressure, Q-switched, cw discharge CO₂ laser were as low as 60 μJ. The laser cavity employed a multiple-pass off-axis path resonator in a ring configuration. CF₄ laser power at 615 cm^?1 and a 1-kHz repetition rate exceeded 300 μW.     

High repetition rate burst-mode spark gap

Results are presented on the design and testing of a pressurized gas blown spark-gap switch capable of high repetition rates in a burst mode of operation. The switch parameters which have been achieved are as follows: 220 kV, 42 kA, a five-pulse burst at 1 kHz, 12-ns rise time, 2-ns jitter at a pulsewidth of 50 ns.     

Scaling of KrF lasers for inertial confinement fusion

The scaling and design principles for a MJ-scale krypton fluoride laser are derived and applied. First, the scaling limits of size and operation of a single large-aperture module (oscillator or amplifier) are explained, and its performance evaluated. A new scheme for combining amplifier modules into high output power chains is then presented. The performance of this architecture is investigated, showing that it effectively produces both the total energy and pulselength required for inertial confinement fusion using existing technology, while maintaining an easily manageable level of system complexity and acceptable low flux levels on optical elements.     

High repetition rate electrooptic Q-switching of Nd3+:YAG lasers showing strong optical birefringence

Using a novel configuration of two coupled resonators, electroopticQ-switching of CW-pumped Nd³⁺:YAG lasers has been investigated. This technique yields two linearly polarized output beams with practically all the power contained in one beam. In the case of strong pumping, e.g., using high repetition rate flashlamp pumping, the optimization of mirror reflectivity leads to a single-resonator configuration.     

High repetition rate TEA CO2laser

This correspondence reports on the successful operation of a TEA CO2laser at rates up to 1000 pps with an average output power up to 65 W over long periods of time. An essential feature of the present system is a rapid gas circulation transverse to the laser axis combined with a large volume of ambient gas. It is found that decomposition of the gas is one of the major problems at high repetition rates.     

Return current in large aperture electron-beam-excited KrF lasers

Results from a model for an e-beam excited KrF laser are presented, and the effects of return currents on plasma parameters and laser performance are discussed. The author finds that the joule heating caused by the return currents, expressed as a fraction of total power deposition, increases with increasing halogen density, increasing aperture size, increasing pressure, and decreasing power deposition. The return current electric field causes a decrease in the rate coefficients for dissociate recombination and attachment and an increase in the rate of multistep ionization. As a result, the electron density near the foil increases by more than tens of percentage points. The laser intensity in those regions also increases. These effects are practically important in lasers having apertures exceeding 1 m     

二极管泵浦的声光Q开关高重频Nd:YAG激光器研究

采用光纤耦合输出的连续激光二极管端面泵浦声光Q开关Nd:YAG激光器,在重复频率1kHz时,获得最窄脉宽5.5ns,最大峰值功率76kW;在重复频率20kHz时,最大平均功率4W（脉宽16ns）,斜效率达33.4％。并对实验结果进行了讨论。     

Theoretical studies of UV-preionized transverse discharge KrF and ArF lasers

A theoretical model has been developed to examine the behavior of UV preionized, fast transverse discharge, rare-gas halide lasers. The model integrates the time dependent circuit equations for the discharge, the kinetic equations for the important atomic and molecular species and electrons, and the equations describing the growth of the spontaneous and stimulated emission. Results of KrF and ArF are compared with those in a companion experimental paper by Sze and Loree. The effects of various self-absorption mechanisms in the laser media are discussed, along with the possible impact of several uncertainties regarding the fundamental processes occurring in such lasers.     

Single-shot, high repetition rate metallic pattern transfer

A flexible high-speed fabrication of relatively thick (about 1 μm) and large (about 120×120 μm) thin film metal pads with a laser-induced forward transfer technique using femtosecond laser pulses (fs-LIFT) will be discussed. Possible applications are thickening of thin film contact pads for wire bonding, the deposition of solder pads or the frequency or electrical resistance tuning of discrete devices. The use of ultrashort laser pulses instead of nanosecond laser pulses reduces the melting problem, increases the quality and the adhesion of the transferred metal pads and allows the transfer of complete disks out of thin films (<1 μm thickness). The combination of ultrashort laser pulses with a pre-structuring of the metal film improves the geometry of the pads and increases the film disk thickness (>1 μm). As a example the transfer of 0.76- and 1.8 μm thick gold/tin disks with a single laser pulse are presented.     

Diode-pumped passively mode-locked Nd:YVO/sub 4/ lasers with 40-GHz repetition rate

We present two different diode-pumped passively mode-locked Nd:YVO/sub 4/ lasers with a repetition rate of 40 GHz. This is the highest repetition rate demonstrated so far with diode-pumped 1-/spl mu/m solid-state lasers. The first laser design allows short pulses of 2.7-ps duration whereas the second laser design is optimized for high average output power of up to 288 mW. We compare both design approaches and show that there is a tradeoff between output power and pulse duration.     

高稳定主被动锁模重复率Nd~(3 ):YAG激光器

本文介绍的是利用可饱和吸收体五甲川与100兆赫驻波型声光调制器联合运行的主被动锁模重复率Nd~(3 ):YAG激光器。在正常运转的情况下,它是借助于声光调制“窗口”有效地克服“尖峰”群的随机竞争,从而获得既稳又窄的光脉冲输出的。 通过下列途径和措施增强了稳定性和多功能性: 1.采用频率合成式高频大功率声光驱动源,有效地克服因环境温度变化、介质加工精度等因素造成的声光街射效率下降和消失的特点。 2.采用机械组合式的一体化染料盒,有效地克服籽腔振荡。     

An experimental and theoretical study of high repetition rate Q-switched Nd: YA1G lasers

An acoustooptic loss modulator made by bonding an X-cut quartz transducer to a fused silica scattering medium offers a practical means for repetitively Q-switching continuously pumped Nd : YAlG lasers at repetition rates up to 50 kHz. The peak power output of a multitransverse mode laser is typically enhanced by a factor of about 500 relative to CW operation at low (≪5 kHz) repetition rates and by larger factors when the transverse mode structure is suitably restricted. At high repetition rates, the peak power becomes smaller and the average power output approaches the CW level. The theoretical Q-switching behavior derived from the rate equations governing an ideal four-level laser is presented in graphical form, and is found to describe the observed behavior well when the laser is restricted to oscillation in the TEM00transverse mode. Similar calculations for Q-switched intracavity second harmonic generation indicate that the peak output power available at the second harmonic slightly exceeds that available at the fundamental, and that the harmonic coupling necessary to optimally couple the Q-switched laser is several orders of magnitude smaller than that required for CW intracavity conversion. Experiments using Ba2NaNb5O15For intracavity Q-switched harmonic generation roughly verified these predictions. A peak power output of 220 watts at 0.532 µ in the TEM00mode was achieved. Surface pitting of the nonlinear crystal after a few hours of operation prevented a thorough comparison with the calculated results. Preliminary experiments using the doubled Q-switched Nd : YAlG laser and an ammonia dihydrogen phosphate crystal to generate ultraviolet (the 0.266-µ harmonic) yielded a peak output power of 40 watts.     

半导体泵浦被动调Q高重频Nd:YAG激光器

从被动调Q固体激光器的速率方程出发,分析给出了Cr4+:YAG被动Q开关Nd:YAG激光脉冲的峰值功率、脉冲能量、脉宽及重频等相关参量表达式.以此为基础,进行了光纤耦合输出的连续半导体激光纵向泵浦被动Q开关Nd:YAG激光器实验研究,采用不同参数Cr4+:YAG晶体作为被动Q开关,获得了不同参数的高重频脉冲激光输出.     

Topologically multicharged and multihumped rotating solitons in wide-aperture lasers with a saturable absorber

We present results of a semianalytical and numerical study of transverse two-dimensional stationary and oscillating solitons in a wide-aperture laser with a saturable absorber and fast nonlinearity of both gain and absorption. We determine the stability conditions and bifurcations of axially symmetric solitons with screw wavefront dislocations of different order. We demonstrate the existence of asymmetric rotating laser solitons with different numbers of intensity maxima.     

Excimer laser with high repetition rate for DUV lithography

The 248nm wavelength of the KrF excimer laser is the accepted tool for the production of structures in the range of 0.25μm. When going to below 0.20μm, the even shorter excimer wavelength of 193nm will be used. The demands on the laser source have changed over the last years for both the reflective and the refractive Step&Scan tools. The cost-effective operation of such lithography tool requires excimer lasers with high power and repetition rates of ≥ 1kHz. Precise dose control of the exposure requires high repetition rate and stability of the laser output energy.