共查询到20条相似文献,搜索用时 46 毫秒
1.
Ultrabroadband continuum generated in air (down to 230 nm) using ultrashort and intense laser pulses
We present results on supercontinuum generation extended up to 230 nm in air during the propagation of a powerful femtosecond laser pulse. The broad supercontinuum generated in air is contributed by self-phase modulation and self-steepening of the fundamental laser pulse, the third-harmonic pulse and their interaction. In particular, the strong interaction between the fundamental and the third-harmonic pulses leads to broad and efficient continuum generation of the third-harmonic pulse itself. The spectrum of the third-harmonic generated in air extends over several tens of nm and overlaps with the shorter wavelength extent of the fundamental continuum. PACS 42.65.Ky; 42.65.Jx; 52.35.Mw 相似文献
2.
M. Kolesik G. Katona J.V. Moloney E.M. Wright 《Applied physics. B, Lasers and optics》2003,77(2-3):185-195
Comprehensive model and computer simulations of the supercontinuum generation in bulk media are presented. Using water and air as representative condensed and gaseous media, the standard model for white-light generation is put to test. It is shown that besides the intensity clamping and plasma-induced frequency blue shift, the linear chromatic dispersion plays an important role. It is the major factor that determines the achievable spectral extent of the supercontinuum. PACS 42.65.-k; 42.65.Hw; 42.65.Ky; 42.65.Sf 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.
M. Spanner M. Pshenichnikov V. Olvo M. Ivanov 《Applied physics. B, Lasers and optics》2003,77(2-3):329-336
We describe the virtues of the pump–probe approach for controlled supercontinuum generation in nonlinear media, using the example of pulse compression by cross-phase modulation in dielectrics. Optimization of a strong (pump) pulse and a weak (probe) pulse at the input into the medium opens the route to effective control of the supercontinuum phases at the output. We present an approximate semi-analytical approach which describes nonlinear transformation of the input pulse into the output pulse. It shows how the input and the output chirps are connected via a time-warp transformation which is almost independent of the shape of the probe pulse. We then show how this transformation can be used to optimize the supercontinuum generation to produce nearly single-cycle pulses tunable from mid-infrared to ultraviolet. PACS 42.65.Re; 42.65.Ky 相似文献
5.
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
6.
R. Sai Santosh Kumar S. Sree Harsha D. Narayana Rao 《Applied physics. B, Lasers and optics》2007,86(4):615-621
We present here an enhanced broadband supercontinuum generation in a potassium di-hydrogen phosphate (KDP) crystal. The enhancement
in the bandwidth of the white light is obtained towards the shorter wavelength regime (<400 nm) by employing supercontinuum
generation and sum frequency generation in tandem. The tunability in the blue region of the spectrum with angle is demonstrated.
The bandwidth of supercontinuum achieved spans from 350 nm to 1300 nm. Further, we show the excellent polarization maintenance
of continuum generated in KDP in comparison to that generated in water and BK-7 glass.
PACS 42.65.Ky; 42.65.Jx; 42.65.Re; 42.25.Ja 相似文献
7.
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
8.
Broadband and supercontinuum pulses with a linear chirp define a linear transform, mapping the difference between the instantaneous frequencies of pump pulses onto the delay time between these pulses. This delay between the pump pulses can be then mapped onto the spatial coordinate with the use of a broad-beam wave-mixing or pump–probe geometry. The new possibilities offered by these mappings for four-wave-mixing techniques are discussed. The spectral and temporal resolution of chirped-pulse wave-mixing and pump–probe techniques are examined. Single-shot multidimensional wave-mixing techniques using broadband and supercontinuum chirped pulses are discussed. PACS 42.65.Dr; 42.65.An 相似文献
9.
G. Sansone G. Steinmeyer C. Vozzi S. Stagira M. Nisoli S. De Silvestri K. Starke D. Ristau B. Schenkel J. Biegert A. Gosteva U. Keller 《Applied physics. B, Lasers and optics》2004,78(5):551-555
Ultrabroadband chirped mirrors with a bandwidth of 270 THz have been manufactured using the BASIC design approach. These mirrors were used to compress the supercontinuum of cascaded hollow fibers down to 4.6 fs. The pulse duration was measured with spectral phase interferometry for direct electric-field reconstruction (SPIDER). PACS 42.65.Re; 42.65.Wi; 42.79.Fm 相似文献
10.
It is demonstrated numerically that the supercontinuum generation and third-harmonic generation that accompany optical filamentation in nonlinear dispersive bulk media can be described as first-order scattering processes akin to the first Born approximation. In particular, for an incident ultrashort pulse the angularly resolved spectrum of the transmitted pulse is shown to be accurately determined using first-order scattering of the incident field from the nonlinearly modified refractive index due to the optical filament. Thus, although an optical filament is a highly nonlinear object, the accompanying supercontinuum generation and third-harmonic generation are driven parametrically by the filament and have negligible back action upon it. 相似文献
11.
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
12.
C. von Korff Schmising M. Bargheer M. Kiel N. Zhavoronkov M. Woerner T. Elsaesser I. Vrejoiu D. Hesse M. Alexe 《Applied physics. B, Lasers and optics》2007,88(1):1-4
Intensity correlations and noise reduction are observed and characterized in the broadband supercontinuum generated by spatio-temporal
solitons propagating in air, i.e., in filamentation of ultrashort laser pulses. Large correlations and reduction of the laser
noise are observed already at the first steps of the filamentation process, while further propagation results in cascaded
χ(3) broadening processes and yield complex correlation maps. The spectral range yielding an optimal laser noise reduction of
3.6 dB is found to cover 10 nm around the fundamental wavelength.
PACS 42.65.Jx; 42.65.Tg; 42.65.Ky; 42.50.Lc 相似文献
13.
Focusing 800-nm pulses of 10–20 fs and ≤0.4 mJ into atmospheric-pressure argon gives rise to a supercontinuum extending down to 250 nm. We show that spectral cuts from this radiation can be shortened by a simple prism compressor down to 30 fs even near the UV cut-off. The resulting pulses have enough energy (several hundred nanojoules) to serve as a simple and rugged broadly tunable pump source in ultra-fast transient spectroscopy. Such an application is demonstrated for the first time, using pulses tuned over 280–320 nm to excite Cr(CO)6; probing it by intense-field ionization at 800 nm, we determine the lifetime of initially populated states to be as short as 14 fs.PACS 42.65.Jx; 42.65.Ky; 42.65.Re; 42.72.Bj; 82.20.-w; 82.53.-k 相似文献
14.
D. Türke W. Wohlleben J. Teipel M. Motzkus B. Kibler J. Dudley H. Giessen 《Applied physics. B, Lasers and optics》2006,83(1):37-42
Manipulation of the input pulse chirp during supercontinuum generation in tapered fibers provides precise control of the soliton
fission process taking place in the taper waist. Simulations and experiments demonstrate that controlling this pre-chirp by
a pulse shaper can be applied to compensate for deleterious effects due to untapered fiber pigtails. Temporal and cross-correlation
frequency resolved measurements are utilized to show, that the control of the soliton fission dynamics can be obtained by
manipulating the input pulse chirp through the imposition of a quadratic spectral phase.
PACS 42.65.Wi; 42.65.Tg; 42.81.Qb; 42.81.DP 相似文献
15.
M. Laroche P. Leproux V. Couderc C. Lesvigne H. Gilles S. Girard 《Applied physics. B, Lasers and optics》2007,86(4):601-604
We report on the experimental demonstration of a supercontinuum generation in a highly birefringent nonlinear microstructured
optical fiber by use of a sub-nanosecond passively Q-switched Yb-doped double-clad fiber laser. The powerful, low-cost sub-nanosecond
pulses produced by the fiber laser source permit one to generate a flat supercontinuum between 1064 and 1600 nm and a more
structured spectral broadening down to 400 nm is also initiated.
PACS 42.65.Wi; 42.55.Wd 相似文献
16.
Supercontinuum generation is dependent on the polarization state of the incident laser. The polarization of the generated supercontinuum is the same as that of the incident laser. The magnitude of the generated supercontinuum depends on the polarization of the incident laser and increases as the polarization changes from circular to linear, irrespective of the nature of the sample, be it isotropic, anisotropic, or chiral. In all samples, the polarization dependence indicates a preference for the linear component of the incident laser beam. The anisotropic sample shows an additional difference in the generated supercontinuum for the two perpendicular directions of the incident laser polarization. PACS 42.25.Ja; 42.65.Ky 相似文献
17.
Ultrashort pulse propagation and supercontinuum generation in tapered and microstructured optical fibers is usually simulated using the corrected nonlinear Schrödinger equation. One of the underlying approximations is the use of a wavelength-independent effective area or, equivalently, of a constant nonlinear coefficient . In very thin waveguide structures with strong light confinement, including silica wires and sub-micron tapered fibers and some microstructured fibers, the validity of such an approximation comes into question. In this paper we present an improved model in which all modal properties are fully taken into account as functions of the wavelength. We use comparative numerical simulation to identify certain regimes in which an improved model is needed for quantitatively correct results. PACS 02.70.Hm; 02.60.Cb; 42.65.Wi; 42.65.Re; 42.81.Pp 相似文献
18.
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
19.
D.A. Akimov M. Schmitt R. Maksimenka K.V. Dukel’skii Y.N. Kondrat’ev A.V. Khokhlov V.S. Shevandin W. Kiefer A.M. Zheltikov 《Applied physics. B, Lasers and optics》2003,77(2-3):299-305
A new design of supercontinuum-generating microstructure fibers is demonstrated, with supercontinuum emission produced in six submicron-diameter cores surrounding a larger central core with a diameter of 2 to 5 m. Such a multiple-core microstructure-fiber design not only allows the total energy of supercontinuum emission to be increased, but also offers a practical way of fabricating microstructure-integrated bundles of small-core high-index-step fibers with very large lengths. Submicron-core fused-silica microstructure fibers are shown to provide maximum ratios of the fiber-core-confined laser power to the fiber-core diameter, allowing limiting waveguide enhancement factors to be approached for a broad class of nonlinear-optical processes contributing to supercontinuum generation. PACS 42.65.Wi; 42.81.Qb 相似文献
20.
F. Théberge W. Liu S. A. Hosseini Q. Luo S. M. Sharifi S. L. Chin 《Applied physics. B, Lasers and optics》2005,81(1):131-134
The distance-resolved spectral intensity distribution of the backscattered light from long filaments generated in air using ultra-short and intense laser pulses is presented. A clean fluorescence spectrum from N2 molecules and ions, which is produced by the high peak intensity inside the plasma filament of the fundamental pulse, was clearly resolved from the backscattered supercontinuum. The supercontinuum generated by both the fundamental and the third-harmonic pulses developed progressively and became fully developed only at the end of the filamentation. 相似文献