共查询到20条相似文献,搜索用时 31 毫秒
1.
为充分利用氟化氪(KrF)准分子激光放大器的长泵浦时间,探索提高激光输出效率的方法,开展紫外超短脉冲在KrF准分子激光器中多脉冲放大和组束的实验研究。采用双脉冲放大方案研究激光脉冲时间间隔对输出能量的影响,确定延时时间,提高脉冲总能量并有效抑制自发辐射(ASE)。实现了单次放大4个紫外超短脉冲,获得了近4倍于单脉冲放大的输出能量。并探索紫外超短激光脉冲的组束技术,成功应用光学角多路的方法将两个亚皮秒的紫外激光脉冲进行精确组束。 相似文献
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We report pulsed homodyne detection of squeezed pulses at a repetition rate of 76 MHz. Measurement of individual pulses, which were interrogated by the correlation coefficient between adjacent pulses, was realized. A homodyne detector was constructed using a low-noise, high-speed operational amplifier; it had a usable bandwidth of 250 MHz. We observed 2.3 dB of squeezing in both the time and frequency domains. 相似文献
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Frequency-domain spectroscopy requires long pulses, whereas time-domain spectroscopy requires short pulses. This Letter demonstrates both theoretically and experimentally that simultaneous detection in frequency and time generates well-resolved spectra using intermediate-length pulses. In the case of coherent Raman spectroscopy, typical femtosecond pulses lie between the time and frequency domains. To demonstrate this method, a high-resolution Raman spectrum of nitrobenzene is obtained from 60 fs pulses. Phase control, pulse shaping, or pulses of widely differing duration are not required. 相似文献
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M. Kakehata R. Ueda H. Takada K. Torizuka M. Obara 《Applied physics. B, Lasers and optics》2000,70(7):S207-S213
Time-dependent polarization pulses are generated by combining two perpendicularly polarized, high-intensity laser pulses. The time evolution of the polarization state of the combined laser pulse is measured by the POLLIWOG technique. We observed changes in the polarization state while varying the relative delay. In order to investigate the effect of pulse combination on the ionization of atoms, the electron signals and the ion signals are measured by irradiating combinations of two perpendicularly polarized pulses or two parallel polarized pulses. With the two parallel polarized pulses, high-order fringe-resolved autocorrelations are obtained by measuring the time-integrated ion signals as a function of the time delay. When two perpendicularly polarized pulses are combined, the fringe period of the time-integrated electron signal as a function of the time delay is different from that of the time-integrated ion signal. This is due to the fact that the electron signal depends on the direction of the field vibration and the number of generated electrons. We also measured the electron energy distributions at different relative delays and confirmed that these depend on the polarization state of generated pulses. 相似文献
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Tóth C Faure J van Tilborg J Geddes CG Schroeder CB Esarey E Leemans WP 《Optics letters》2003,28(19):1823-1825
The temporal shape (rise time, fall time, skewness) of 50-200-fs Ti:sapphire laser pulses has been controlled by appropriate adjustment of a grating-pair compressor. It was found that the skewness of the laser pulse envelope is particularly sensitive to the third-order component of the spectral phase. Introducing such a third-order phase offset by detuning the grating pair relative to the optimum pulse compression settings allowed the generation of skewed pulses. As an example of an application, these skewed pulses were used to optimize a laser-plasma electron accelerator. 相似文献
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Thorsten Ulm Harry Fuchs Andreas Klehr Edeltraud Gehrig 《Optics Communications》2008,281(8):2160-2166
The amplification of ps and fs pulses with peak powers of up to 4.5 kW has been investigated in a single quantum well InGaAs tapered amplifier. The pulses with durations of 100 fs or 2 ps were generated by a modelocked titanium-sapphire laser. The amplified pulses indicate strong gain saturation and carrier generation due to photon absorption in the laser active region which causes a temporal broadening of the amplified pulses as well as modifications of the optical spectrum. The gain recovery time was measured by a pump-probe experiment. The experimental results are analyzed with respect to the sub-ps gain dynamics which is described by a relaxation time approximation. 相似文献
8.
1.3μmDFB半导体激光超短脉冲的产生及其压缩 总被引:2,自引:1,他引:1
本文首次报道1.3μm单模超短脉冲产生及压缩实验。通过梳状波电脉冲直接调制DCPBH-DFB半导体激光器,获得22ps单模光滑脉冲;然后利用G-T干涉仪压缩得到近变换极限超短脉冲。脉宽为9.3ps,峰值功率超过200mW,重复频率1GHz,时间带宽乘积为0.39,脉冲压缩比为2.4。最后对实验结果进行了讨论。 相似文献
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We describe the generation of subpicosecond electrical pulses by optical rectification of ultrashort optical pulses. The electrical pulses are generated by the second-order nonlinear response of a LiTaO(3) crystal bonded to a coplanar transmission line. A bipolar temporal waveform with a width of 875 fs was measured after a propagation distance of 175mum . This pulse width was limited by the response time of the photoconductive sampler. We observed both broadening and amplitude reduction in the temporal waveform owing to propagation. 相似文献
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J. Kerdiles 《Optical and Quantum Electronics》1969,1(4):193-195
In this experiment, the transmission of the saturable absorber of a mode-locked laser is modulated optically by a train of ultra-short pulses emitted by another laser, with some power reflected inside the cavity to initiate the emission. The laser threshold is only attained during the opening time of the modulator, and stimulated emission is prevented at any other time. Once pulses are formed, the photon density is sufficiently high for auto-modulating the dye.Q-switching of the laser is only realised if the difference between the time of a round-trip in the cavity and the period of modulation is less than ±17 psec. The emission is a series of pulses of 5.2 nsec period lasting for 60 nsec. The total energy in all pulses is 60 mJ for a neodymium doped glass rod of 8 mm diameter.We describe a method for measuring the noise of the series of pulses using a saturated photo-cell. We find a ratio of 100 between the energy of one pulse and the energy emitted between two pulses. 相似文献
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Weiner AM 《Optics letters》2000,25(16):1207-1208
In a recent Letter [Opt. Lett. 25, 132 (2000)] the properties of two different techniques for time reversal of ultrafast optical waveforms were compared. Although both techniques, spectral phase conjugation and spectral inversion, perform the same function for real pulses, for pulses with complex envelope functions it was asserted that only spectral inversion gives true time reversal. I argue here for a different interpretation. 相似文献
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In order to obtain pulses of maximum energy and minimum time, the passive mode-locking regime was optimized for the yttrium aluminate-neodymium laser on the basis of a range of polymethine dyes with different nonlinear parameters (bleaching intensity and relaxation time). Ultrashort pulses with a minimum time of 5 ps and power 0.4 GW were generated. The radiant strength of yttrium aluminate was estimated and found to be 1.3 GWcm–2 for ultrashort pulses (USP). Dyes were identified which provided for the USP minimum time and maximum energy. A pulse time of 5 ps was found to be limiting for the given radiant strength of the crystal. 相似文献
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In this paper, a wire-cylinder electrode system was designed to study the negative DC corona pulses due to the influence of AC voltage applied to an adjacent conductor. The corona onset voltage and distribution pattern and the parameters of the corona current pulses such as the rise time, pulse duration and the average pulse amplitude are systematically analyzed. The AC voltage is found to have an interesting modulation effect on the time interval of the current pulses. At last, based on a simplified ion cloud model, a full explanation is given to reveal the mechanism behind the influence of the AC voltage on negative DC corona. 相似文献
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Yuan J Madore B Panych LP 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2011,208(2):219-224
Fat suppression is important but challenging in balanced steady-state free precession (bSSFP) acquisitions, for a number of clinical applications. In the present work, the practicality of performing fat-water selective excitations using spatial-spectral (SPSP) RF pulses in bSSFP sequence is examined. With careful pulse design, the overall duration of these SPSP pulses was kept short to minimize detrimental effects on TR, scan time and banding artifact content. Fat-water selective excitation using SPSP pulses was demonstrated in both phantom and human bSSFP imaging at 3T, and compared to results obtained using a two-point Dixon method. The sequence with SPSP pulses performed better than the two-point Dixon method, in terms of scan time and suppression performance. Overall, it is concluded here that SPSP RF pulses do represent a viable option for fat-suppressed bSSFP imaging. 相似文献
17.
Benjamín Alonso Miguel Miranda Francisco Silva Vladimir Pervak Jens Rauschenberger Julio San Román Íñigo J. Sola Helder Crespo 《Applied physics. B, Lasers and optics》2013,112(1):105-114
We have post-compressed 25 fs (Fourier limit) amplified pulses in an argon-filled hollow-core fiber. The output pulses were compressed using a pair of wedges and chirped mirrors down to 4.5 fs (Fourier limit of 4.1 fs), which corresponds to less than two optical cycles. We then performed the characterization of the pulses by combining the d-scan and the STARFISH techniques. The temporal (and spectral) measurement of the pulses is done with d-scan, which is used as the reference to extend the characterization to the spatiotemporal (and spatiospectral) amplitude and phase of the pulses by means of STARFISH. The post-compressed pulses at the output of the hollow-fiber had an energy of 150 μJ. The analysis of the pulses revealed larger spectral broadening and blue-shift, and shorter duration at the center of the beam. For the first time, we demonstrate the complete characterization of intense ultra-broadband pulses in the sub-two-cycle regime, which provides an improved insight into the properties (space–time and space–frequency) of the pulses and is highly relevant for their applications. 相似文献
18.
Investigation of plumes produced by material ablation with two time-delayed femtosecond laser pulses
We experimentally investigated and herewith reported the results of laser ablation of copper and gold with two time-delayed femtosecond laser pulses at 800 nm in vacuum. The ablation plume dynamic was monitored by fast plume imaging and time- and space-resolved optical emission spectroscopy. Optical microscopy was used to follow the ablation depth as a function of the delay between the two laser pulses. Nanoparticles deposition on mica substrates was analysed by atomic force microscopy.We estimate roughly the plume's atomization degree - that is the mass fraction of atomized material over the total ablated mass - from the relative intensities of radiation emitted from atoms and nanoparticles. It is shown that the atomization degree depends critically on the time delay between both laser pulses and on the characteristic time of electron-lattice relaxation. The increase of the atomization degree is accompanied by the decrease of the ablation depth. Atomic force microscopy measurements confirm the partial atomization of nanoparticles, as the analyses of particle deposition on mica substrates show a large decrease of the number of nanoparticles for large delay between the two pulses. 相似文献
19.
Some statistical features of microdischarges running near the metal-insulator interfaces have been discussed. The study has verified an exponential character of statistical distributions of the time intervals between microdischarge pulses, power-law distribution of voltage peaks of these pulses (height of pulses) and very weak correlation effects among pulses, i.e. weak time-height correlation, time autocorrelation and height autocorrelation. A statistical parameter of the power law distribution of the heights of microdischarge pulses proved to be sensitive to the voltage load of the insulating interface metal-insulator. 相似文献
20.
Interference of dissociating wave packets in the I2 molecule driven by femtosecond laser pulses
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The interference between two dissociating wave packets of the I2 molecule driven by femtosecond laser pulses is theoretically studied by using the time-dependent quantum wave packet method.Both the internuclear distanceand velocity-dependent density functions are calculated and discussed.It is demonstrated that the interference pattern is determined by the phase difference and the delay time between two pump pulses.With two identical pulses with a delay time of 305 fs and a FWHM of 20 fs,more interference fringes can be observed,while with two pump pulses with a delay time of 80 fs and a FWHM of 20 fs,only a few interference fringes can be observed. 相似文献