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1.
We compare the cladding patterns present in grating structures fabricated with an ultrafast laser and a phase mask with a cw beam interference model. We find that the observed patterns agree well with the model results for picosecond pulses; however, for femtosecond pulses, we show that the full bandwidth and the pulsed nature of the sources must be considered because the pattern can be affected by group-velocity walk-off. An interesting consequence of order walk-off is the possibility of pure two-beam interference generation with a phase mask in the femtosecond pulse regime. 相似文献
2.
Efficient nonlinear Bragg diffraction was observed as an intense infrared femtosecond pulse was focused on a plasma grating induced by interference between two ultraviolet femtosecond laser pulses in air. The preformed electrons inside the plasma grating were accelerated by subsequent intense infrared laser pulses, inducing further collisional ionization and significantly enhancing the local electron density. 相似文献
3.
Field-free molecular orientation induced by combined femtosecond single- and dual-color laser pulses:The role of delay time and quantum interference
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The coherent control of field-free molecular orientation of CO with combined femtosecond single- and dual-color laser pulses has been theoretically studied. The effect of the delay time between the femtosecond single- and dual-color laser pulses is discussed, and the physical mechanism of the enhancement of molecular orientation with pre-alignment of the molecule is investigated. It is found that the basic mechanism is based on the creation of a rotational wave packet by the femtosecond single-color laser pulse. Furthermore, we investigate the interference between multiple rotational excitation pathways following pre-alignment with femtosecond single-color laser pulse. It is shown that such interference can lead to an enhancement of the orientation of CO molecule by a factor of 1.6. 相似文献
4.
Yoshio Hayasaki Maki Nishitani Hidetomo Takahashi Hirotsugu Yamamoto Akihiro Takita Daichi Suzuki Satoshi Hasegawa 《Applied Physics A: Materials Science & Processing》2012,107(2):357-362
In holographic femtosecond laser processing, diffractive parallel pulses are distorted by phase discontinuities and mutual
interference between the neighborhoods in the reconstructed image of a Fourier computer-generated hologram when the interval
is smaller than the beam diameter. We investigated holographic fabrication on a glass surface using parallel pulses with different
intervals. We found the closest parallel pulses with sufficient separation to avoid mutual interference in holographic femtosecond
laser processing. The minimum interval was 2.8 times larger than the diffracted beam diameter. The experimental results were
also supported by a computer simulation. Our findings will be very useful in the design of holographic laser processing systems. 相似文献
5.
《中国物理 B》2015,(8)
Digital holography can be applied to ultrafast detection when a femtosecond laser pulse is used. In this paper, the interference process of two femtosecond laser pulses is studied and the recording process of the femtosecond laser pulsed digital hologram is simulated. Holograms at different recording angles are generated by integrating the instantaneous interference field. By analyzing the distribution of the reconstructed phase error, the characteristics of femtosecond laser pulsed digital holography are discussed. 相似文献
6.
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
7.
We provide what is believed to be the first experimental evidence of spatial control on multiple filamentation (MF) using circularly polarized femtosecond laser pulses. The exceptional shot-to-shot reproducibility of the MF pattern allowed complete characterization of the two copropagating high-energy filaments, revealing for the first time temporal (self-) compression of circularly polarized filamenting pulses to a fifth of the initial 57 fs laser pulse duration without any sophisticated chirp control. Compared with LP MF, an enhancement in spatial stability and an increase in energy throughput are reported for circular input polarization. 相似文献
8.
We introduce a novel method to generate the optical vortex with computer-generated hologram (CGH) fabricated inside glass by femtosecond laser pulses. The CGH was directly written inside glass by femtosecond laser pulses induced microexplosion without any pre- or post-treatment of the material. We also realized the restructured optical vortex beams of both the transmission and reflection pattern with high fidelity using a collimated He-Ne laser beam. The total diffractive efficiency of both the transmission and reflection pattern is about 4.79%. 相似文献
9.
Andrés F. Lasagni Peng Shao Charles M. Shaw Suman Das 《Applied Surface Science》2010,256(6):1708-9305
A simple optical interference method for the fabrication of simply periodic and periodic with a substructure on poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) using femtosecond laser interference patterns is demonstrated. The femtosecond laser pulse was split by a diffractive beam splitter and overlapped with two lenses. Homogeneous periodic arrays could be fabricated even using a single laser pulse. In addition, multipulse irradiation resulted in reproducible sub-wavelength ripples oriented perpendicularly to the laser polarization with spatial period from 170 to 220 nm (around one-fourth of the laser wavelength). In addition, the observed size of the spatial period was not affected by the number of incident laser pulses or accumulated energy density. Using high energy pulses it was possible to completely remove the PEDOT:PSS layer without inducing damage to the underneath substrate. 相似文献
10.
A simple interference model is proposed for conical emission frequency-angular spectrum formation during the filamentation
of femtosecond laser pulse in a nonlinear dispersive medium. The model allows to obtain analytical expressions for frequency-angular
distributions of the supercontinuum spectral components of pulses at different wavelengths in media with arbitrary material
dispersion law. The model reproduces the supercontinuum frequency-angular spectrum transformation for the case of laser pulse
splitting into several subpulses and for multiple refocusing of the light field in filament. Frequency-angular spectra analytically
calculated from the proposed interference model are in good agreement with the results of numerical simulations performed
for the filamentation of femtosecond laser pulses in fused silica. 相似文献
11.
R. Szip?cs A. K?házi-Kis P. Apai E. Finger A. Euteneuer M. Hofmann 《Applied physics. B, Lasers and optics》2000,70(7):S63-S66
Phase properties of optical thin film interference filters are discussed from the aspect of their usage for phase-error free wavelength separation of broadband femtosecond laser pulses. It is shown that both transmissive or reflective interference filters with high contrast ratios exhibit high cubic phase shifts on transmission or reflection, respectively, causing intolerable distortion in the temporal pulse shape. We show, however, that high efficiency wavelength separation of broadband femtosecond laser pulses can be achieved by using low contrast, properly designed reflective optical interference filters directly built into the cavity of the broad spectrum, femtosecond pulse lasers or parametric oscillators. For demonstrative purposes, we implemented the idea for a Kerr-lens mode-locked Ti:sapphire laser, and obtained two-color, inherently synchronized, unchirped, femtosecond pulse outputs from a single laser oscillator. 相似文献
12.
研制了一套基于多光子脉冲内干涉相位扫描方法的可以同时对飞秒激光脉冲进行相位测量和补偿的实验系统装置.实验中,通过自主研发的LabVIEW程序控制液晶空间光调制器和光纤光谱仪,对待测飞秒激光脉冲施加相位扫描,并同时记录受到调制的飞秒激光脉冲的倍频光谱,得到了多光子脉冲内干涉相位扫描(MIIPS)轨迹图.通过MIIPS轨迹图的三次测量和迭代运算,还原出了经过预先啁啾调制的中心波长约为810 nm、重复频率为1 kHz的飞秒激光脉冲的光谱相位,测量精度在0.1 rad以内.根据测量结果,利用液晶空间光调制器对该飞秒激光脉冲进行相位补偿,得到了近似傅里叶变换极限的飞秒激光脉冲.这一装置将在多光子显微成像、脉冲整形、飞秒激光光谱学等众多领域发挥重要作用. 相似文献
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15.
The nanostructures with dimensions (110–250 nm), much smaller than the wavelength of laser light, obtained on surfaces of
various semiconductors under the action of laser ablation by femtosecond pulses are studied. Nanostructures obtained at large
angles of incidence and under the action of interference of two femtosecond pulses on the surface of the samples are analyzed.
Original Russian Text ¢ R.A. Ganeev, T.Q. Jia, 2008, published in Optika i Spektroskopiya, 2008, Vol. 105, No. 1, pp. 154–159. 相似文献
16.
Physics of the Solid State - The dynamics of Newton interference rings appearing in the ablation area on the surface of various condensed media under irradiation with femtosecond laser pulses is... 相似文献
17.
P. Rudolph J. Bonse J. Krüger W. Kautek 《Applied Physics A: Materials Science & Processing》1999,69(7):S763-S766
Laser ablation with femtosecond pulses (130 fs, wavelength 800 nm, repetition rate 2 Hz) was compared with nanosecond-pulse ablation (10 ns, wavelength 266 nm, repetition rate 2.5 Hz) of bariumalumoborosilicate glass in air using the direct focusing technique. Different ablation thresholds and heat-affected zones were observed. The lateral and vertical machining precision was evaluated. Single nanosecond laser pulses in the far UV resulted in a bubble or a circular hole in the centre of the illuminated spot, depending on the applied fluence. The ablation behaviour in the case of near-IR femtosecond pulses contrasted to this. Bubble formation was not detected. It needed repeated pulses at the same spot to modify the surface until material removal could be observed (incubation). Cavity dimensions of less than the beam diameter were achieved in this case. 相似文献
18.
Yang H Zhang J Zhang Q Hao Z Li Y Zheng Z Wang Z Dong Q Lu X Wei Z Sheng Z Yu J Yu W 《Optics letters》2005,30(5):534-536
We investigate polarization-dependent properties of the supercontinuum emission generated from filaments produced by intense femtosecond laser pulses propagating through air over a long distance. The conversion efficiency from the 800-nm fundamental to white light is observed to be higher for circular polarization than for linear polarization when the laser intensity exceeds the threshold of the breakdown of air. 相似文献
19.
The Talbot effect under illumination of double femtosecond laser pulses has been reported. Spectrums of double femtosecond laser pulses with phase differences are quite different from that of one single femtosecond laser pulse. Therefore, the Talbot images of the double femtosecond laser pulses with phase differences are different from that of one single femtosecond laser pulse. Specifically, for the phase difference corresponding to π, the Talbot image shows the largest difference from that of one single pulse. Experimental results are in good agreement with the theoretical analysis. The behaviors of Talbot images under double femtosecond laser pulses illumination cannot be obtained under one femtosecond laser pulse, monochromatic or polychromatic light illumination. Therefore, it is a new interesting optical phenomenon for the Talbot effect which should have potential applications. 相似文献