共查询到20条相似文献,搜索用时 31 毫秒
1.
A.J. Verhoef J. Seres K. Schmid Y. Nomura G. Tempea L. Veisz F. Krausz 《Applied physics. B, Lasers and optics》2006,82(4):513-517
High intensity contrast ratio, pre-pulse free pulses with pulse duration of 5 fs and pulse energy of 1 mJ were generated at a repetition rate of 1 kHz by compressing the output pulses of a multi-stage Ti:sapphire laser amplifier system in a Ne-gas-filled hollow fibre. The spatial and temporal properties of the output laser beam were fully characterised. PACS 42.60.Jf; 42.65.Re; 42.81.Qb 相似文献
2.
F. Théberge J. Filion N. Aközbek Y. Chen A. Becker S.L. Chin 《Applied physics. B, Lasers and optics》2007,87(2):207-210
Self-stabilization of the laser pulse parameters is demonstrated during the two-color filamentation of ultrashort and intense
laser pulses in gases. Experimental data and results of numerical simulations show, in good qualitative agreement, that the
root-mean-square values of the intensity fluctuations decrease below the initial value for the near-infrared pump pulse and
the perturbative limit for the third-harmonic pulse in the filament. It is found that the stabilization of the third-harmonic
intensity and energy are due to intensity clamping of the pump pulse and a constant ‘volume’ of the laser pulse during the
nonlinear propagation inside the filament.
PACS 42.65.Ky; 42.65.Jx; 52.35.Mw 相似文献
3.
N. Aközbek A. Becker M. Scalora S.L. Chin C.M. Bowden 《Applied physics. B, Lasers and optics》2003,77(2-3):177-183
The continuum generation by intense femtosecond IR laser pulses focused in air including the effect of third-harmonic generation is investigated. We have used a theoretical model that includes the full spatio-temporal dynamics of both the fundamental and the third-harmonic pulses. Results of our numerical calculations show that a two-color filamentation effect occurs, in which the third-harmonic conversion efficiency remains almost constant over the whole filament length. It is found that this effect is rather independent of the wavelength of the input beam and the focal geometry. During the filamentation process the third-harmonic pulse itself generates a broad continuum, which can even overlap with the continuum of the fundamental pulse for the longer pump wavelengths. In consequence, the continuum generation generated by intense IR laser pulses is further extended into the UV. PACS 42.65.Jx; 42.65.Ky; 52.35.Mw 相似文献
4.
N. Kortsalioudakis M. Tatarakis N. Vakakis S.D. Moustaizis M. Franco B. Prade A. Mysyrowicz N.A. Papadogiannis A. Couairon S. Tzortzakis 《Applied physics. B, Lasers and optics》2005,80(2):211-214
Harmonic generation during the self-guided propagation of femtosecond ultraviolet (UV) laser pulses (248-nm, 450-fs) in argon is investigated. The third (82.7-nm) and fifth (49.6-nm) harmonics are generated in the UV filament. The energy-conversion efficiencies for the harmonics are found to be at least two orders of magnitude higher than those reported in the literature for similar gas pressures. The enhancement is attributed to the quasi-phase matching of the harmonics due to the self-guiding of the driving pulse. PACS 42.25.Bs; 42.65.Jx; 42.65.Re; 42.65.Ky 相似文献
5.
We present measurements of the performance characteristics of few-cycle laser pulses generated by propagation through a gas-filled hollow fiber. The pulses going into the fiber and the compressed pulses after the fiber were simultaneously fully characterized shot-by-shot by using two kHz SPIDER setups and kHz pulse energy measurements. Output-pulse properties were found to be exceptionally stable and pulse characteristics relevant for non-linear applications like high-harmonic generation are discussed. PACS 42.65.Re; 42.65.Ky; 42.65.Sf; 42.65.Jx 相似文献
6.
George Heck 《Optics Communications》2006,259(1):216-222
We demonstrate control over the spatial coordinates (position and extent) of white light filaments (supercontinuum generation) in an aqueous solution. These are the first experiments to achieve control of filament position through the manipulation of the spectral phase of an ultra-fast (50 fs) 800 nm excitation laser pulse. A closed feedback loop employing a spatial light modulator and a genetic algorithm was used to manipulate the spectral phase of the pulses to achieve a specified filament position and length. 相似文献
7.
We demonstrate a direct and versatile scheme to determine the carrier-envelope phase fluctuations of tunable ultrashort optical pulses. The spatial interferogram between the high frequency components and the parametrically amplified and frequency doubled low frequency components of an octave broad white light continuum is measured for every single pulse. It directly reveals the carrier-envelope phase fluctuations of the pump pulses from the regenerative amplifier, as well as of the white light and the tunable pulses generated from it. PACS 42.25.Kb; 42.65.Yj; 42.65.Re 相似文献
8.
Filamentation nonlinear optics 总被引:1,自引:0,他引:1
A filamenting femtosecond laser pulse self-stabilizes the intensity fluctuation inside the filament core due to intensity
clamping and generates an excellent spatial beam quality inside the core due to self-spatial filtering. The high quality of
the core can be sampled by nonlinear processes. A few experimental examples are shown: self-phase modulation, four-wave mixing,
third-harmonic generation and waveguide writing in glass.
PACS 42.65.Jx; 52.35.Mw 相似文献
9.
We show through simulations how to control the spatial field distribution of a tightly focused Gaussian beam of polarization-shaped
femtosecond laser pulses. The field in the focus is calculated employing a decomposition into plane-wave components with appropriate
incidence angles. Both polarization directions of the shaped pulse are treated separately and then superposed coherently.
The incident polarization shape can be used to control the spatial and temporal evolution of the longitudinal field component.
PACS 42.25.Ja; 42.30.-d; 42.65.Re 相似文献
10.
T. Imahoko K. Takasago T. Sumiyoshi H. Sekita K. Takahashi M. Obara 《Applied physics. B, Lasers and optics》2007,87(4):629-634
We have developed a 6–12 μm mid-infrared (MIR) femtosecond laser source for glyco-protein structure analysis. The MIR femtosecond
laser pulses are generated by a differential frequency generation (DFG) configuration with a combination of Ti:sapphire based
regeneratively amplified femtosecond laser pulses (780 nm, 160 fs, 1 mJ) and a β-BaB2O4 (BBO) based optical parametric amplifier (OPA). The MIR pulse energy exceeds 4.5 μJ, where a glyco-protein molecule has resonant
absorption lines due to the vibrational–rotational transitions. The pulse width is estimated to be less than 1 ps according
to the cross correlation measurement between the two OPA output pulses. Using the MIR femtosecond laser pulses, we demonstrated
photo-dissociation of the sialyl Lewis X (sLeX) proton added ion, which is the first time to the best of our knowledge.
PACS 42.65.Re; 42.62.-b; 42.60.-b; 42.65.-k; 87.50 相似文献
11.
P. Nuernberger G. Vogt R. Selle S. Fechner T. Brixner G. Gerber 《Applied physics. B, Lasers and optics》2007,88(4):519-526
We experimentally demonstrate a method to generate shaped femtosecond laser pulses in the ultraviolet at a central wavelength
of 267 nm, the third harmonic of conventional titanium-sapphire femtosecond laser systems. Employing a 128-pixel liquid-crystal
spatial light modulator, we impose variable spectral phase modulations upon the near-infrared laser pulses. By this, complex
laser pulses can be shaped whose overall spectrum is still conserved. Our experiments show that it is possible to easily transfer
these pulses into the ultraviolet at 267 nm via sum-frequency mixing in nonlinear crystals and to predictably generate multistructured
ultraviolet femtosecond laser pulses. We analyze the temporal and spectral composition of these pulses after frequency conversion
into the ultraviolet using difference-frequency cross-correlation and XFROG (cross-correlation frequency-resolved optical
gating) techniques with an unmodulated fundamental laser pulse. The method can be employed to facilitate adaptive quantum
control experiments in the ultraviolet wavelength regime, where the major absorption bands of many organic molecular systems
are located.
PACS 42.65.Re; 42.72.Bj; 32.80.Qk 相似文献
12.
We present a flashlamp-pumped Nd:YAG laser simultaneously emitting pulse structures on microsecond, nanosecond and picosecond time scales. Within a microsecond flashlamp pump pulse a nonlinear reflector based on stimulated Brillouin scattering (SBS) generates several Q-switch pulses. The phase-conjugating effect of the SBS reflector provides a compensation of phase distortions generated inside the laser rod, resulting in transverse fundamental mode operation. Additional acousto-optic loss modulation inside the resonator leads to mode locking. As a result, each Q-switch pulse is subdivided into several picosecond pulses. Energies of up to 2 mJ for the mode-locked pulses with durations between 220 and 800 ps are demonstrated. The wide variability of the lasers temporal output parameters as well as its high beam quality make it a splendid tool for fundamental research in laser materials processing. PACS 42.60.Fc; 42.60.Gd; 42.65.Es 相似文献
13.
Y. Chen F. Théberge C. Marceau H. Xu N. Aközbek O. Kosareva S.L. Chin 《Applied physics. B, Lasers and optics》2008,91(2):219-222
We observed a new filamentation nonlinear process: continuous self-frequency down shift inside the filament zone during the
propagation of a femtosecond laser pulse in air. The frequency shift depends strongly on the length of the self-guided column
(filament).
PACS 42.65.Dr; 42.65.Jx; 52.35.Mw 相似文献
14.
Intense ultrashort laser pulses with stabilized carrier-envelope phase (CEP) are generated at 800 nm by using multi-stage collinear and non-collinear optical parametric amplifiers (OPAs). The first-stage collinear OPA is directly pumped by the fundamental-wave pulses and tuned to generate idler pulses at 1600 nm, which are further amplified by a second-stage collinear OPA, and then frequency-doubled to generate CEP-stabilized pulses at 800 nm. A non-collinear OPA is used to amplify the CEP-stabilized pulses at 800 nm. The combination of different OPAs can generate and amplify CEP-stabilized pulses at 800 nm without any detrimental influence from the fundamental-wave pulses. The CEP stabilization is verified with a simple and robust spectral interference setup. The stable interference pattern is measured for every single pulse and compared with the unstable pattern from pulses of random CEP. PACS 42.65.Re; 42.65.Yj; 42.25.Kb 相似文献
15.
We investigate the coherence properties of a linear array of white-light sources produced in bulk media by ultrashort laser pulses. The array is generated out of the spatial interference pattern between two laser pump pulses, so that the number of supercontinuum sources and their separations can be easily manipulated by varying the geometry of the laser beam interaction. We find that all the secondary white-light sources which arise from the generation of filaments in the optical medium are well phase-locked and are thus able to generate stable and high-visibility multiple-beam interference patterns in the far-field. Observations are compared to the results of a simple model which takes into account a clamping of the peak laser intensity inside the filaments and includes intensity-dependent phase shifts among the different sources. PACS 42.65.Jx; 42.65.Ky; 42.65.Re 相似文献
16.
V.P. Kandidov N. Akozbek M. Scalora O.G. Kosareva A.V. Nyakk Q. Luo S.A. Hosseini S.L. Chin 《Applied physics. B, Lasers and optics》2005,80(2):267-275
We propose a new method for controlling randomly generated multiple filaments during the propagation of femtosecond laser pulses in optical media. The method is based on introducing a periodic amplitude modulation of the transverse beam profile. It is shown both experimentally and numerically that the introduction of a periodic mesh into a propagation path of a femtosecond near-infrared laser pulse leads to a deterministic spatial distribution of multiple filaments in the presence of initial random fluctuations. As a result, the number of filaments is increased as compared to the random case. PACS 42.65.Jx; 42.25.Bs; 42.60.Jf 相似文献
17.
《中国光学快报(英文版)》2015,(3)
Filamentation-induced water condensation and snow formation are investigated using laser pulses with different chirps and pulse widths. Chirped pulses result in the laser filamentation with different spatial lengths and intensities, which has a great impact on airflow motion and snow formation. The experiments show that snow formation mainly relates to the filament intensity distribution. Negative chirped pulses produce a greater amount of snow because of higher intensity inside the filaments as compared with the positive chirped pulses. 相似文献
18.
We report an experimental investigation of the spectro-temporal dynamics of the pulse formation in Q-switched Nd:YAG lasers and in nanosecond optical parametric oscillators (OPOs). The temporal evolution of the spectral intensity distribution of the light pulses was measured with a 1-m Czerny–Turner spectrometer in combination with a fast streak camera. This detection system allows the analysis of temporal changes in the spectrum of single nanosecond pulses. The measurements were performed for a flashlamp-pumped, Q-switched Nd:YAG laser and for an unseeded as well as for a seeded singly-resonant nanosecond OPO. The laser output spectrum varies strongly from pulse to pulse and even within a single pulse due to mode beating. In an unseeded OPO, individual spectral modes start to oscillate statistically from the parametric noise for pump powers close to the OPO threshold. With increasing pump power a strong modulation in the spectral formation of the pulse is observed, resulting from a strong interaction of parametric conversion and back conversion of signal and idler radiation into pump radiation. By means of injection seeding, the starting condition was controlled for a single mode. Due to the seed radiation, the seeded mode starts sooner than the unseeded modes. These are suppressed completely in the case of sufficient seed power and moderate pump power. The observations are in good agreement with results of corresponding numerical simulations. PACS 42.65.Sf, 42.65.Yj 相似文献
19.
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
20.
Self-transformation of a powerful femtosecond laser pulse into a white-light laser pulse in bulk optical media (or supercontinuum generation) 总被引:2,自引:0,他引:2
V.P. Kandidov O.G. Kosareva I.S. Golubtsov W. Liu A. Becker N. Akozbek C.M. Bowden S.L. Chin 《Applied physics. B, Lasers and optics》2003,77(2-3):149-165
We present experimental and theoretical results on white-light generation in the filamentation of a high-power femtosecond laser pulse in water and atmospheric air. We have shown that the high spatio-temporal localization of the light field in the filament, which enables the supercontinuum generation, is sustained due to the dynamic transformation of the light field on the whole transverse scale of the beam, including its edges. We found that the sources of the supercontinuum blue wing are in the rings, surrounding the filament, as well as at the back of the pulse, where shock-wave formation enhanced by self-steepening takes place. We report on the first observation and demonstration of the interference of the supercontinuum spectral components arising in the course of multiple filamentation in a terawatt laser pulse. We demonstrate that the conversion efficiency of an initially narrow laser pulse spectrum into the supercontinuum depends on the length of the filament with high intensity gradients and can be increased by introducing an initial chirp. PACS 42.65.Jx; 42.65.Re; 42.25.Bs; 42.50.Hz 相似文献