Relationship of self-focusing to spatial instability modes

Campillo, A. J.; Shapiro, S. L.; Suydam, B. R.

doi:10.1063/1.1655142

Cited by 103 publications

(16 citation statements)

References 2 publications

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“…Besides their ability to collapse and self-compress, femtosecond pulses with high enough intensity can also become modulationally unstable and decay into multiple filaments under the action of the local ambient noise [9][10][11]. The consequence is rather catastrophic, in the sense that this "multifilamentation" breaks the homogeneity of the laser focal spot through the random nucleation of filaments.…”

Section: Introductionmentioning

confidence: 99%

Multifilamentation of powerful optical pulses in silica

2010

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The multiple filamentation of powerful light pulses in fused silica is numerically investigated for central wavelengths at 355 nm and 1550 nm. We consider different values for beam waist and pulse duration and compare the numerical results with behaviors expected from the plane-wave modulational instability theory. Before the nonlinear focus, the spatiotemporal intensity patterns can be explained in the framework of this theory. Once the clamping intensity is reached, for long input pulse durations (∼1 ps), the ionization front defocuses all trailing components within a collective dynamic, and a spatial replenishment scenario takes place upon further propagation. Short pulses (∼50 fs) undergo similar ionization fronts, before an optically turbulent regime sets in. We observe moderate changes in the total temporal extent of ultraviolet pulses and in the corresponding spectra. In contrast, infrared pulses may undergo strong temporal compression and important spectral broadening. For short input pulses, anomalous dispersion and self-steepening push all pulse components to the trailing edge, where many small-scaled filaments are nucleated. In the leading part of the pulse, different spatial landscapes, e.g., broad ring patterns, may survive and follow their own propagation dynamics.

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Section: Introductionmentioning

confidence: 99%

Multifilamentation of powerful optical pulses in silica

2010

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“…The spatial laser beam profile causes a spatial refractive index profile and leads to self-focusing [1][2][3][4][5][6]. The overall beam profile is responsible for whole-beam self-focusing while an intensity modulation of the spatial intensity distribution leads to a beam break-up (small-scale selffocusing) [5][6][7][8]. The combined effects of self-focusing and beam diffraction result in filament formation [1][2][3][4][5][9][10][11][12].…”

Section: Pacsmentioning

confidence: 99%

Determination of nonlinear refractive indices by external self-focusing

Meier

Penzkofer

1989

Appl. Phys. B

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The nonlinear refractive index of benzene is determined by measuring the reduction of the beam divergence of picosecond ruby laser pulses when passing through a benzene sample. Time-integrated spatial beam profiles give an effective refractive index while time-resolved beam profiles measured with a streak camera allow the determination of the temporal evolution of the nonlinear refractive index. PACS:42.65, 42.65.J At high laser powers the refractive index of materials becomes intensity dependent. The spatial laser beam profile causes a spatial refractive index profile and leads to self-focusing [1][2][3][4][5][6]. The overall beam profile is responsible for whole-beam self-focusing while an intensity modulation of the spatial intensity distribution leads to a beam break-up (small-scale selffocusing) [5][6][7][8]. The combined effects of self-focusing and beam diffraction result in filament formation [1][2][3][4][5][9][10][11][12]. The self-focusing increases the pulse intensity enormously and enhances all nonlinear optical effects [13][14][15][16][17][18][19]. The abrupt rise of nonlinear optical effects is an indication of self-focusing and may be used to determine the self-focusing length. The determination of the nonlinear refractive index from the abrupt rise of nonlinear optical effects is complicated by the fact that either whole-scale self-focusing or small-scale selffocusing may act and the small-scale self-focusing parameters (ripple widths and modulation depths) are difficult to determine.The vagueness of whole-scale or small-scale selffocusing dynamics may be avoided by changing from internal self-focusing (focal point caused by nonlinear refractive index is inside sample) to external selffocusing (focal point is outside sample) [1 ]. In this case the nonlinear refractive index of the sample causes a reduction of the overall beam divergence and the effects of small ripples across the beam profile may be neglected.In our experiments we determine the reduction of beam divergence by comparing the beam diameters (FWHM) of two pulses at a certain distance behind the sample position, where one pulse passes through the sample and the other pulse is bypassed. Our timeresolved measurements of the beam diameters with a streak camera and a two dimensional readout system allow the study of the instantaneous and transient contributions to the nonlinear refractive index [12,18,20]. The effective time-averaged and the time-resolved nonlinear refractive index of benzene are measured with picosecond light pulses of a ruby laser. The reported time-averaged nonlinear refractive index coefficients n 2 of benzene vary by a factor of ten in the region between n 2 = 1.4x 10~2 1 m 2 V~2 and lxlO" 20 m 2 V-2

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“…For the ultrahigh powers ͑P ӷ 100P cr ͒, as is the case in our experiment, multifilamentation occurs through modulational instability that breaks up the beam into periodic cells over very short propagation distances z fil Ϸ 2P cr / ͑ 0 I 0 ͒Ϸ1 -3 m for an incident intensity I 0 ϳ 4- comb beam structure, the cells of light being separated by "bridges." [13][14][15] These structures appear as dark straight lines on the beam profile recorded on a photosensitive paper after only 11 m propagation ͑Fig. 1͒.…”

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confidence: 99%

32 TW atmospheric white-light laser

Béjot

Bonacina

Extermann

et al. 2007

Applied Physics Letters

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Ultrahigh power laser pulses delivered by the Alisé beamline (26J, 32TW pulses) have been sent vertically into the atmosphere. The highly nonlinear propagation of the beam in the air gives rise to more than 400 self-guided filaments. This extremely powerful bundle of laser filaments generates a supercontinuum propagating up to the stratosphere, beyond 20km. This constitutes the highest power “atmospheric white-light laser” to date.

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Relationship of self-focusing to spatial instability modes

Cited by 103 publications

References 2 publications

Multifilamentation of powerful optical pulses in silica

Multifilamentation of powerful optical pulses in silica

Determination of nonlinear refractive indices by external self-focusing

32 TW atmospheric white-light laser

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