Kerr-induced spontaneous Bessel beam formation in the regime of strong two-photon absorption

Abstract

Abstract:We study the effect of Two-Photon Absorption (TPA) nonlinear losses on Gaussian pulses, with power that exceeds the critical power for self-focusing, propagating in bulk kerr media. Experiments performed in fused silica and silicon highlight a spontaneous reshaping of the input pulse into a pulsed Bessel beam. A filament is formed in which sub-diffractive propagation is sustained by the Bessel-nature of the pulse.References and links 1. R. Boyd, Nonlinear Optics (Academic Press, 1992). 2. G. G. Luther, J. V. Moloney, and A. C. Newell, "Self-focusing threshold in normally dispersive media," Opt. Lett. 19, 862-864 (1994)

Sharply autofocused ring-Airy beams transforming into non-linear intense light bullets

“…This type of non-linear ring formation depends on the multiphoton order of the non-linear absorption and is discussed in details in the case of two-photon absorption in ref. 24.…”

Spatio-temporal dynamics of femtosecond laser pulses at 1550 nm wavelength in crystal silicon

“…Note, that the increase of Δt of the on-axis part of the pulse, recorded both in bright-field-and polarized light microscopy, cannot be attributed to the linear dispersion in silicon, which broadens the input 100 fs pulse to 265 fs in 8 mm propagation according to [2]. Considering the subsequent pulse narrowing at longerτ, the maximum propagation distance that is only 0.6 mm in Fig.…”

“…3b). As will be shown below, and according to [2,3], at sufficient pulse energy and increased thickness of the c-Si sample, actual shape of the pump beam becomes distorted by TPA and plasma refraction. Indeed, we found, that in 8-mm-thick c-Si sample, where the shape of the pump beam, focused on the exit face of the sample, is surely not Gaussian, the profile of TH emission acquires a ring component (Fig.…”

“…2c, d correspondingly. Taking into account that according to [2], the laser pulse of the energy E p = 70 nJ with λ p = 1.55 µm and Δt p = 100 fs in c-Si has the power of 24 critical energies of self-focusing P crit , we assume that in our case, the critical power of self-focusing for the pulse of temporal width Δt p = 450 fs corresponds to the pulse energy E p = 12 nJ. Proceeding from this, and also from the fact that the widths of the spectral bands in Fig.…”

“…However, peculiarities of propagation and spatio-temporal transformation of 1550-nm fs laser pulses in c-Si are still poorly understood, though their knowledge is strongly needed for optimization of the process of fs laser modification. Propagation of the fs laser pulses at 1.55 µm wavelength in c-Si was studied in [2] the regime of strong TPA. Interaction of fs laser pulses at 1200 nm wavelength with c-Si was reported in [3,4].…”