共查询到20条相似文献,搜索用时 31 毫秒
1.
Liqiang FengTianshu Chu 《Physics letters. A》2011,375(41):3641-3648
In the present Letter, we theoretically discuss the optimum conditions for generating ultrashort attosecond pulse in three-color field with a model He exposed to the intense 5 fs, 800 nm fundamental field and the two weak control fields of 25 fs, 400 nm and 25 fs, 1600 nm. Through investigating the controlling factors in HHG spectra generation via manipulating the laser parameters of the three fields, we demonstrate that properly increasing the pulse intensity of 800 nm and 1600 nm fields at the same time with zero phase effects is an effective way to generate short attosecond pulses. Finally, an isolated pulse of 7 as is predicted by Fourier transforming an ultrabroad XUV continuum of 393 eV with phase compensation. 相似文献
2.
E. Riedle M. Beutter S. Lochbrunner J. Piel S. Schenkl S. Spörlein W. Zinth 《Applied physics. B, Lasers and optics》2000,71(3):457-465
Noncollinearly phase-matched optical parametric amplifiers (NOPAs) pumped by the blue light of a frequency-doubled Ti:sapphire
regenerative amplifier are a convenient source of continuously tunable ultrashort pulses in the visible and near infrared
for spectroscopic experiments. We present the underlying principles, report recent improvements and describe the experiences
gained from the routine use of a number of NOPAs in our laboratories. We find that the setup can easily be optimized for the
given experimental requirements. Typical output-pulse energies in the visible are 5 to 10 μJ and a few μJ in the NIR from
200 μJ regenerative-amplifier pulses at 800 nm. From 460 to 700 nm, pulse lengths between 10 and 20 fs are routinely achieved,
while the length increases monotonically from about 20 fs at 900 nm to just below 50 fs at 1600 nm. In all cases this corresponds
to a dramatic shortening compared to the length of the pump pulses of around 100 fs. First results show that the 700 to 900 nm
region can be accessed with sub-50-fs pulse lengths by use of an intermediate white-light generator in a two-stage setup.
Received: 29 November 1999 / Published online: 5 July 2000 相似文献
3.
孤立阿秒脉冲因可以跟踪和控制原子及分子内电子的运动过程而备受关注.本文从理论上开展了氦原子在3束飞秒脉冲激光组合场辐照下产生的高次谐波和阿秒脉冲辐射的研究.组合激光场由16 fs/1600 nm,15 fs/1100 nm和5.3 fs/800 nm的钛宝石脉冲构成.与前两束脉冲合成的双色场产生谐波谱相比,附加钛宝石脉冲的三色场产生的高次谐波发射谱呈现出高转换效率及宽带超连续特性,超连续谱范围覆盖从230—690次谐波,傅里叶变换后实现了128 as高强度孤立短脉冲的产生.该结果归因于合成的三色场呈现出高功率及少周期的中红外飞秒脉冲激光特性,可以有效控制原子电离以及复合发生在中红外飞秒脉冲的一个有效光学周期内. 相似文献
4.
We theoretically propose a three-color laser scheme to enhance the high-order harmonic intensity and generate an isolated attosecond pulse. By adding a 3 fs, 1600 nm laser pulse to a synthesized two-color laser field (5 fs, 800 nm and 10 fs, 1200 nm), the harmonic intensity is effectively enhanced and an isolated attosecond pulse with duration 41 as is generated. In this scheme, the short trajectory is suppressed, the selection of the long quantum path can be achieved. We also investigate emission time of harmonics in terms of the time-frequency analysis and the semi-classical three-step model to illustrate the physical mechanism of high-order harmonic generation. 相似文献
5.
We theoretically investigate high-order harmonic and isolated attosecond pulse generation in a two-color chirped laser field,which is synthesized by a 9 fs/800 nm fundamental chirped pulse and a 9 fs/1600 nm controlling chirped pulse.Our numerical results show that,by using this method,not only is the harmonic cutoff significantly extended to the 948th order harmonic,but also the bandwidth of the supercontinuum spectrum is effectively broadened to about 1342 eV.In addition,due to the introduction of the chirp,the long quantum path is suppressed and only the short one is selected,and then an isolated 28 as pulse with a bandwidth of 155 eV is obtained directly. 相似文献
6.
数值研究了双色激光脉冲与一维氩原子相互作用的谐波发射功率谱.双色激光脉冲由800 nm和1600 nm的两束激光组成,脉冲持续时间为9.7 fs.计算结果表明,相对相位为π时,谐波截止频率从单色场情形的58 eV大幅度地展宽到316 eV,获得频宽为93 eV的软X射线连续辐射谱.此外,还采用短程的普薛耳-特勒势和长程的软化库仑势进行比对,数值结果表明该连续辐射谱的存在具有普适性.通过半经典的“三步”模型和时频分析小波变换方法对该连续辐射谱进行分析,发现其主要由单一的“短”量子路径生成,直接叠加频率从22
关键词:
红外双色激光脉冲
连续辐射谱
阿秒脉冲 相似文献
7.
设计了一种由类噪声脉冲抽运的全光纤结构平坦超连续谱光源。在色散管理掺铒光纤激光器中通过调节腔内偏振态,在泵浦功率为450 mW时,实现了稳定的类噪声脉冲锁模,锁模脉冲的中心波长为1 600 nm,脉冲宽度为303 fs。在最大泵浦功率为1 W时,谐振腔直接输出功率为8.6 mW。较低的功率无法有效拓展超连续谱宽度,为此设计一种掺铒光纤放大器进行功率放大,放大器最大输出功率为338 mW,将功率放大后的类噪声脉冲耦合进高非线性光纤以产生超连续谱,超连续谱的20 dB光谱范围为1 530 nm~2 300 nm,在1 736 nm~2 134 nm范围内,光谱的平坦度优于0.5 dB。 相似文献
8.
We propose a method to extend the high-order harmonics plateau and generate an isolated sub-10-as pulse by adding a weak control pulse (10 fs, 1600 nm) to modify a two-color laser field (5 fs, 800 nm; 10 fs, 400 nm). The numerical results show that the plateau is extended obviously in the three-color laser field regime. Additionally, the ionization rate and classical returning kinetic-energy maps are calculated to better understand the physical origin of the high-order harmonics generation (HHG). By means of the ionization probability and the time-frequency distributions, more features of the HHG are revealed. Furthermore, our simulations show that the width of the plateau and the relative conversion efficiency of the harmonic spectra are highly dependent on the relative phase. Finally, by adjusting the relative phase and superposing a properly selected range of the HHG spectrum, an isolated attosecond pulse with a duration of 7 as is obtained. 相似文献
9.
C. Jordan K. A. Stankov G. Marowsky E. J. Canto-Said 《Applied physics. B, Lasers and optics》1994,59(4):471-473
Femtosecond pulses at 496 nm were Raman-shifted in methane with 20% efficiency. The pulse duration could be reduced up to 6.5 times from 560 fs at the fundamental to 85 fs at the Stokes frequency (580nm), which is the shortest pulse duration generated in this way. It was shown experimentally that chirped-pulse Raman scattering avoids the limitations arising from self-phase modulation. 相似文献
10.
We investigate the potential of four-wave mixing in dielectric hollow waveguides for vacuum ultraviolet pulse generation with unprecedented short durations. Taking into account higher-order transverse modes and plasma effects we predict the generation of a 2.5 fs pulse at 160 nm using an intense 10 fs, 800 nm pulse and its weaker third harmonic at 267 nm, both coupled to the fundamental transverse mode. Excitation of higher transverse modes allows an increase of the signal energy (up to by a factor of 20) but with a pulse duration of 13 fs (compressible to 7.7 fs). 相似文献
11.
O.G. Kosareva N.A. Panov D.S. Uryupina M.V. Kurilova A.V. Mazhorova A.B. Savel’ev R.V. Volkov V.P. Kandidov S.L. Chin 《Applied physics. B, Lasers and optics》2008,91(1):35-43
We have identified the pulse self-compression region in a filament produced by 55 fs, 4 mJ, 805 nm radiation propagating in
air without geometrical focusing. In our experiment the pulse self-compression region is attained by the propagation distance,
where the shortest wavelength in the supercontinuum blue wing reaches a minimum, and the growing conversion efficiency to
white light has a large gradient. Numerical tracking of the pulse along the filament shows a single-peak 9 fs pulse with a
flat spectral phase at the optimum compression distance.
PACS 42.65.Jx; 42.65.Re; 42.65.Ky 相似文献
12.
We present an Er-doped fiber(Er:fiber)-based femtosecond laser at 780 nm with 256 MHz repetition rate, 191 fs pulse duration, and over 1 W average power. Apart from the careful third-order dispersion management, we introduce moderate self-phase modulation to broaden the output spectrum of the Er:fiber amplifier and achieve 193 fs pulse duration and 2.43 W average power. Over 40% frequency doubling efficiency is obtained by a periodically poled lithium niobate crystal. Delivering through a hollow-core photonic bandgap fiber, this robust laser becomes an ideal and convenient light source for two-photon autofluorescence imaging. 相似文献
13.
N. S. Shahabuddin H. Mohamad M. A. Mahdi Z. Yusoff H. Ahmad S. W. Harun 《Laser Physics》2012,22(1):212-215
A simple multi-wavelength source is demonstrated based on spectral slicing of supercontinuum (SC) light using a Sagnac loop
mirror. A mode locked fiber laser with pulse width of 800 fs is employed to generate the SC in photonic crystal fiber (PCF).
The SC light extending from 1200 nm up to the wavelength region above 1750 nm is obtained at the amplified pulse pump power
of 30 dBm. By slicing the SC with a loop mirror, a multiwavelength comb spectrum is obtained with different channel spacing
for different operating wavelength region. Spacings of 1.5, 2.3, and 2.9 nm are shown at wavelength regions of 1220, 1450,
and 1730 nm, respectively. It is also observed that the signal to noise ratio (SNR) increases from 15 to 20 dB as the operating
wavelength increases from 1220 to 1730 nm region. 相似文献
14.
《中国物理快报》2017,(7)
We demonstrate a self-starting erbium fiber oscillator-amplifier system based on the nonlinear polarization rotation mode-locked mechanism. The direct output pulse from the amplifier is 47 fs with an average power of 1.22 W and a repetition rate of 50 MHz, corresponding to a pulse energy of 24 nJ. The full width at half-maximum of the spectrum of the output pulses is approximately 93 nm at a central wavelength of 1572 nm so that the transformlimited pulse duration is as short as 39 fs. Due to the imperfect dispersion compensation, we compress the pulses to 47 fs in this experiment. 相似文献
15.
A 49 fs pulse at the wavelength of 800 nm was converted to a 26 fs pulse at the wavelength of 400 nm by temporal stretching (frequency chirping) and second harmonic generation from a chirped pulse with subsequent compression. The energy conversion efficiency of 35% was achieved. 相似文献
16.
利用飞秒抽运探测技术及时间分辨荧光(TRPL)等光谱技术对高等植物LHCⅡ中的超快光动力学过程进行了研究。在其时间分辨荧光光谱中表现出了明显的各向异性特性。实验上观察了LHCⅡ中色素间的能量传递过程,由飞秒动力学发现,单体内Chlb到邻近的Chla之间的能量传递在200~300fs的时间尺度,Chla激子带间的能量弛豫发生在几百飞秒,不同单体Chla分子间能量分布过程在几个皮秒。而时间分辨荧光和飞秒动力学过程中上百皮秒的慢过程归属于不同聚集体间的能量平衡过程或分子构象变化。 相似文献
17.
18.
Coupling femtosecond light pulses from an all-fiber Er:laser system into a dispersion-shifted and highly non-linear fiber, we generate output spectra exhibiting two broadband and mutually coherent maxima. Depending on the chirp of the input pulse, the spectral separation is easily tunable over a wide range up to values exceeding 100 THz. In this way, the source provides access to an ultrabroadband wavelength interval from 1130 to 1950 nm. Because of soliton effects, the long-wave component exhibits a transform-limited pulse width of 40 fs directly after the nonlinear element. The high-frequency part propagating in the dispersive regime is recompressed to pulse durations as short as 24 fs with an optimized prism sequence. 相似文献
19.
The generation of sub-2 fs light pulses in the UV is numerically demonstrated, using frequency conversion in filamentation regime. Few-cycle pulses emitted at 266 nm keep their temporal shape over several tens of centimeters. Self-compression results from the interplay between Kerr self-focusing and a low-density plasma, which continuously defocuses the pulse over extended propagation ranges. 相似文献