On the higher-order Kerr effect in femtosecond filaments

Kolesík, M.; Mirell, Daniel; Diels, Jean‐Claude; Moloney, Jerome V.

doi:10.1364/ol.35.003685

Cited by 46 publications

(36 citation statements)

References 10 publications

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“…[37][38][39][40][41]) will reduce the need to assumeg an initial field with no spatiotemporal dependences or to use apertured FROG traces. Additionally, recent investigations into the possible role of high-order nonlinear optical effects [42][43][44], ionization by multichromatic pulses [45], and the influence of phenomenological parameters (such as the free-carrier collision time and the effective electron mass) [46] may also allow for further improvements in predamage calculations.…”

Section: Discussionmentioning

confidence: 99%

Interaction of ultrashort-laser pulses with induced undercritical plasmas in fused silica

et al. 2012

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R. 2012. Interaction of ultrashort-laser pulses with induced undercritical plasmas in fused silica. Phys Rev A, 85(1):013808.PHYSICAL REVIEW A 85, 013808 (2012) Interaction of ultrashort-laser pulses with induced undercritical plasmas in fused silica Ultrafast light-material interactions near the damage threshold are often studied using postmortem analysis of damaged dielectric materials. Corresponding simulations of ultrashort pulse propagation through the material are frequently used to gain additional insight into the processes leading to such damage. However, comparison between such experimental and numerical results is often qualitative, and pulses near to but not exceeding the damage threshold leave no permanent changes in the material for postmortem analysis. In this article, a series of experiments is presented that measures the near-and far-field properties of a 140-fs laser pulse after propagation through a fused silica sample in which a noncritical electron plasma was generated. Concurrently, results from simulations in which the laser pulse was numerically constructed according to the nearfield beam profile and frequency resolved optical gating (FROG) trace are presented. It is found that to extract a quantitative comparison of such data, cylindrical symmetry of the laser pulse in simulations should be abandoned in favor of a fully 3 + 1D Cartesian representation. Further comparison of experimental and calculated damage thresholds shows that time-corrective effects predicted by the Drude model play a critical role in the physics of both pulse evolution and plasma formation. The influence of resulting spatiotemporal dependences of the pulse in far-field measurements leads to unretrievable FROG traces. However, it is shown through both simulation and experiment that the use of an appropriate beam aperture will eliminate this effect when measuring the temporal pulse amplitude.

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Section: Discussionmentioning

confidence: 99%

Interaction of ultrashort-laser pulses with induced undercritical plasmas in fused silica

et al. 2012

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“…It would overturn the picture most have of the mechanism behind long-range filamentary propagation of intense ultrashort pulses -as arising from an interplay between self-focusing due to the positive optical nonlinearity from bound electrons and defocusing due to the plasma generated by ionization. The existence of a higher-order Kerr effect would also have implications for the general nonlinear susceptibility in transparent media [7,8], including harmonic generation [9][10][11].Subsequent experimental studies of light filaments [12][13][14][15] have not supported the higher-order Kerr model, with one exception [16]. One measurement [13] found that the electron density was two orders of magnitude higher than predicted by a calculation including higher-order nonlinearities, but agreed with a simulation based on plasma defocusing alone [5].…”

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confidence: 99%

Optical Nonlinearity in Ar andN2near the Ionization Threshold

et al. 2011

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We directly measure the nonlinear optical response in argon and nitrogen in a thin gas target to laser intensities near the ionization threshold. No instantaneous negative nonlinear refractive index is observed, nor is saturation, in contrast with a previous measurement [Loriot et al., Opt. Express 17, 13429 (2009)] and calculations [Brée et al., Phys. Rev. Lett. 106, 183902 (2011)]. In addition, we are able to cleanly separate the instantaneous and rotational components of the nonlinear response in nitrogen. In both Ar and N2, the peak instantaneous index response scales linearly with the laser intensity until the point of ionization, whereupon the response turns abruptly negative and ∼constant, consistent with plasma generation.The optical Kerr effect, the intensity-dependent refractive index experienced by an optical pulse in a transparent medium, plays an important role in phenomena from nonlinear propagation in optical fibers [1] to modelocking in pulsed lasers [2] to filamentary propagation in condensed media and the atmosphere [3]. A recent transient birefringence measurement in the components of air reported by Loriot et al. [4] purported to show that the optical Kerr effect saturates and then becomes negative for intensities greater than 26 TW/cm 2 . A strong higher-order Kerr effect, with a crossover from positive to negative nonlinear index at intensities well below the ionization threshold, would have a huge impact on the nonlinear optics of transparent media, and has inspired theoretical works predicting plasma-free light filamentation [5] and exotic new effects in light propagation [6]. It would overturn the picture most have of the mechanism behind long-range filamentary propagation of intense ultrashort pulses -as arising from an interplay between self-focusing due to the positive optical nonlinearity from bound electrons and defocusing due to the plasma generated by ionization. The existence of a higher-order Kerr effect would also have implications for the general nonlinear susceptibility in transparent media [7,8], including harmonic generation [9][10][11].Subsequent experimental studies of light filaments [12][13][14][15] have not supported the higher-order Kerr model, with one exception [16]. One measurement [13] found that the electron density was two orders of magnitude higher than predicted by a calculation including higher-order nonlinearities, but agreed with a simulation based on plasma defocusing alone [5]. A physical mechanism for the saturation and negative response was proposed based on the nonlinear response near the threshold of ionization [17,18]. What is missing from this debate is a direct measurement of the nonlinearity that corroborates or refutes the intensity dependence observed by Loriot et al. Here, we describe such a measurement in Ar and N 2 using spectral interferometry. We find no saturation and no negative instantaneous nonlinear phase, in contrast to the original experiment [4].The technique we use, single-shot supercontinuum spectral interferometry [19], provides...

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“…As a consequence, the HOKE can ensure self-defocusing in filaments and balance Kerr self-focusing [10], in place of the plasma, especially for short pulses [9]. This result raised an active controversy [11][12][13][14][15][16] in the lack of direct experimental confirmation.…”

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Transition from Plasma-Driven to Kerr-Driven Laser Filamentation

et al. 2011

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While filaments are generally interpreted as a dynamic balance between Kerr focusing and plasma defocusing, the role of the higher-order Kerr effect (HOKE) is actively debated as a potentially dominant defocusing contribution to filament stabilization. In a pump-probe experiment supported by numerical simulations, we demonstrate the transition between two distinct filamentation regimes at 800 nm. For long pulses (1.2 ps), the plasma substantially contributes to filamentation, while this contribution vanishes for short pulses (70 fs). These results confirm the occurrence, in adequate conditions, of filamentation driven by the HOKE rather than by plasma. *

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On the higher-order Kerr effect in femtosecond filaments

Cited by 46 publications

References 10 publications

Interaction of ultrashort-laser pulses with induced undercritical plasmas in fused silica

Interaction of ultrashort-laser pulses with induced undercritical plasmas in fused silica

Optical Nonlinearity in Ar andN2near the Ionization Threshold

Transition from Plasma-Driven to Kerr-Driven Laser Filamentation

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