- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Nonlinear Optics || Ultrafast and Intense-Field Nonlinear Optics
摘要： There is currently great interest in the physics of ultrashort laser pulses. Recent advances have led to the generation of laser pulses with durations of the order of 1 attosecond (Hentschel et al., 2001). Ultrashort pulses can be used to probe the properties of matter on extremely short time scales. Within the context of nonlinear optics, ultrashort laser pulses are of interest for at least two separate reasons. The ?rst reason is that the nature of nonlinear optical interactions is often profoundly modi?ed through the use of ultrashort laser pulses, in part because of the broad spectral bandwidth necessarily associated with such pulses. The next two sections of this chapter treat various aspects of the resulting modi?cations of the nature of nonlinear optical interactions. The second reason is that ultrashort laser pulses tend to possess extremely high peak intensities (because laser pulse energies tend to be established by the energy-storage capabilities of laser gain media), and thus short laser pulses tend to have much higher peak powers than longer pulses. The second half of this chapter is devoted to a survey of the sorts of nonlinear optical processes that can be excited by extremely intense laser ?elds.
关键词： attosecond pulses,ultrashort laser pulses,high peak intensities,spectral bandwidth,nonlinear optics
更新于2025-09-23 15:21:01
-
Digitization for Highly Accurate 3D Laser Processing of Customera??specific Tools
摘要： Cutting tool manufacturing by laser technology has developed quickly during the past fifteen years. Compared to conventional machining methods such as grinding or eroding, laser processing does not require any additional elements such as coolant, grinding wheels, erosion wire, discs, etc. If ultrashort laser pulses are used together with optimized laser parameters, heat input into the material can be negligible. Additionally, there are no processing forces or tool wear present during laser manufacturing. For these many reasons, autonomous production of metallic or diamond tools is feasible and highly interesting.
关键词： Autonomous Production,Ultrahard Materials,Laser Micromachining,Ultrashort Laser Pulses,Tool Manufacturing
更新于2025-09-23 15:19:57
-
Attosecond Dynamics of Photoexcitation of the Hydrogen Atom by Ultrashort Laser Pulses
摘要： The dynamics of photoexcitation of the hydrogen atom in the discrete and continuous spectra under the action of laser pulses in the attosecond range of time and pulse durations has been analyzed using perturbation theory. It is shown that over time interval shorter than or on the order of pulse duration, the time dependence of the photoexcitation probability is generally oscillating by nature. It has been established that for certain values of parameters, the envelope of this dependence has a peak, the position of which is determined by the pulse duration and carrier frequency.
关键词： Perturbation theory,Photoexcitation,Hydrogen atom,Attosecond dynamics,Ultrashort laser pulses
更新于2025-09-23 15:19:57
-
One-Step Femtosecond Laser Stealth Dicing of Quartz
摘要： We report on a one-step method for cutting 250-μm-thick quartz plates using highly focused ultrashort laser pulses with a duration of 200 fs and a wavelength of 1030 nm. We show that the repetition rate, the scan speed, the pulse overlap and the pulse energy directly influence the cutting process and quality. Therefore, a suitable choice of these parameters was necessary to get single-pass stealth dicing with neat and flat cut edges. The mechanism behind the stealth dicing process was ascribed to tensile stresses generated by the relaxation of the compressive stresses originated in the laser beam focal volume during irradiation in the bulk material. Such stresses produced micro-fractures whose controlled propagation along the laser beam path led to cutting of the samples.
关键词： ultrashort laser pulses,stealth dicing,transparent materials,heat accumulation,quartz
更新于2025-09-23 15:19:57
-
Antia??Counterfeiting Microstructures Induced by Ultrashort Laser Pulses
摘要： Ultrashort pulsed laser enables selective ablation of metal films on glass substrates, ripple formation on metal surface, and defect generation inside functional glass, etc. Correspondingly, direct writing of computer-generated holograms (CGHs), ripple rendered structure color, and defect featured photostimulated luminescence can be realized. Due to the feature of small size or invisibility, these induced microstructures can be used for anti-counterfeiting.
关键词： ultrashort laser pulses,computer-generated holograms,defects,anti-counterfeiting microstructures,ripples
更新于2025-09-23 15:19:57
-
Stray light autocorrelation for the measurement of ultrashort laser pulses
摘要： Ultrashort laser pulses in the femtosecond range are of growing interest in medicine and micro material processing for industrial applications. The most interesting parameter is the pulse duration, which can only be measured by optical autocorrelation methods incorporating an optically nonlinear medium. Established methods mostly use monocrystalline beta barium borate (BBO) in transmission, exhibiting a high nonlinear conversion efficiency. However, this material is brittle, expensive and sophisticated in adjustment due to the necessary non-collinear phase matching. Since fiber-based high energy femtosecond laser systems become more and more achievable, the conversion efficiency of the nonlinear medium should no longer be seen as the restricting factor. Therefore, this research work discusses the suitability of several nonlinear media with differing translucency. Quartz, ammonium dihydrogen phosphate (ADP) and aluminum nitride (AlN) were compared in a standard autocorrelation setup and a novel versatile setup measuring frequency-doubled stray light. Best results were achieved with AlN, which appears to be a suitable and promising alternative material to BBO, reducing the expenses by two to three orders of magnitude.
关键词： autocorrelation,Stray light autocorrelation,aluminum nitride,ultrashort laser pulses
更新于2025-09-19 17:13:59
-
Quasi single-shot two-pulse tilted pulse front autocorrelator coupled with spatial chirp and spectral divergence monitor for ultrashort pulsed laser beams
摘要： Simultaneous single-shot unambiguous detection and measurement of pulse front tilt, spatial chirp, spectral divergence and pulse width has been carried out using two-pulse tilted pulse-front autocorrelator (TP-TPFAC) coupled with spectral interferometry using small part of laser beam intercepted from Mach Zehnder delay unit of TP-TPFAC generating two delayed and spatially inverted pulses. Error in estimation of rotation angle of autocorrelation (AC) trace due to accidental improper positioning of CCD detector is avoided by measuring angle between AC traces corresponding to two delayed and spatially inverted pulses. Likewise, accuracy in estimation of spatial chirp is improved by using spatially resolved spectral trace of two spatially inverted pulses, as errors due to accidental improper positioning of either grating of spectrograph or CCD detector are avoided. Sensitivities and accuracies of the two methods are compared in different experimental situations. Estimated pulse parameters are found in close accordance with respective theoretical values.
关键词： Chirped pulse amplification,Ultrashort laser pulses,High energy high power lasers
更新于2025-09-19 17:13:59
-
Use of heavily doped germanosilicate fibres with a small core diameter in stretchers of ultrashort laser pulses at a wavelength of 1.03 μm
摘要： The use of a heavily doped germanosilicate fibre with a W-profile refractive index and small core diameter in stretchers of ultrashort laser pulses with their subsequent amplification and compression in all-fibre laser systems is considered. The application of fibres of this type makes it possible to stretch, amplify, and then compress a laser pulse with minimum distortions of its initial shape and width. Due to the dispersion properties of these fibres, which allow the pulse duration to be increased significantly at a small fibre length and the third-order positive dispersion of the diffraction-grating-based output compressor to be compensated for, amplified pulses with an energy of 2 mJ and width of 250 fs, free of a picosecond pedestal, are obtained. Several types of fibres intended for the use in stretchers of ultrashort laser pulses are comparatively analysed from the point of view of their dispersion compatibility with a diffraction-grating-based output compressor.
关键词： nonlinear self-phase modulation,fibre lasers,heavily doped germanosilicate fibre,group-velocity dispersion,femtosecond lasers,amplification of ultrashort laser pulses
更新于2025-09-16 10:30:52
-
Polarization of high-order harmonic generation in oriented molecules with intense ultrashort laser pulses
摘要： Using numerical solutions of the time-dependent Schr?dinger equation we show that in oriented molecules one can control the polarization of molecular high-order harmonic generation (MHOHG) by intense linearly polarized pulses. For oriented triangular molecules, H3+/H32+, one obtains even-order harmonics perpendicular to the laser polarization, whereas all odd-order harmonics have the same polarization as the laser polarization. For H2+/H2 we show that only odd-order harmonics are generated for any orientation and their polarization is nearly parallel to the molecular axis. We describe these phenomena based on perturbation theory. Redshifts of the MHOHG spectra occur due to laser induced electron localization in non-Born-Oppenheimer dissociating molecules, reflecting the effect of nuclear dynamics. The numerical results illustrate the sensitivity of harmonic polarization to molecular geometry and nuclear dynamics.
关键词： oriented molecules,ultrashort laser pulses,perturbation theory,nuclear dynamics,high-order harmonic generation,polarization
更新于2025-09-16 10:30:52
-
Surface structuring of Kapton polyimide with femtosecond and picosecond IR laser pulses
摘要： Pulsed laser ablation is one of the most efficient and clean methods for high-precision processing and modification of polymers and biomaterials. Polymer ablation has been extensively investigated with ultraviolet lasers while little attention has been given to the infrared (IR) region, which becomes particularly interesting with the recent advances in ultrashort laser technologies. Here, we report the results of a comparative study on 1030-nm ultrashort laser structuring of Kapton polyimide, a polymer important in a variety of applications, with direct comparison of 247-fs and 7-ps laser pulses. The laser-induced damage thresholds for both pulse durations have been determined and the femtosecond laser threshold has been found to be considerably lower than that for picosecond pulses (by a factor of ～ 3.5). Both femtosecond and picosecond laser–produced craters have been thoroughly investigated as a function of pulse energy and focusing conditions. It has been demonstrated that femtosecond laser pulses enable accurate polyimide structuring while picosecond irradiation regimes result in a number of undesired effects such as re-deposition of the ablation debris, surface swelling, and the formation of high rims around the ablation craters. The mechanisms of polyimide ablation with femtosecond and picosecond IR laser pulses are discussed.
关键词： crater profile,swelling,laser ablation,damage threshold,laser processing,ultrashort laser pulses,multiphoton absorption,polymers,polyimide
更新于2025-09-12 10:27:22