Discrete damage traces from filamentation of Gauss-Bessel pulses

Abstract

Filamentation of Bessel-Gauss pulses propagating in borosilicate glass is found to produce damage lines extending over hundreds of micrometers and consisting of discrete, equidistant damage spots. These discrete damage traces are explained by self-regeneration of Gauss-Bessel beams during the propagation and are potentially applicable in laser microfabrication of transparent materials.Light filaments formed by laser beams propagating in transparent media present an interesting case of spatial, and possibly, temporal localization of electromagnetic radiation at extremely high power densities sustainable over significant propagation lengths. The potential areas of applications of such light channeling range from remote sensing and LIDAR to laser microscopy and microfabrication. Generation and dynamics of light filaments is explained using a wide range of physical models. Some of them adopt moving focus model [1] which implies that filamentation is merely an optical illusion occurring when time-integrated detection is used. Others describe filaments as self-channelled beams [2, 3] whose stationarity is supported by a balance between Kerr-induced self-focusing and plasma-induced defocusing; a genuine soliton-like propagation, however, is destroyed by additional physical effects [4]. The dynamic spatial replenishment model [5] treats filamentation as a cyclic defocusing and focusing due to the dynamic interplay between the Kerr and plasma effects. According to the recently proposed "filamentation without self-channelling" model [6,7], multiphoton absorption alone can dynamically balance the self-focusing, thus leading to filamentation. It was shown numerically [8] that the absorption transforms the initial Gaussian beam toward the Gauss-Bessel (GB) beam, which is a modified solution of the free-space Helmholz equation [9]. Consequently, filament represents a narrow, high-intensity central part of a GB beam, whose propagation losses are replenished from the low-intensity side lobes containing the main part of the beam's energy. This model is strongly supported by recent experimental and theoretical results [7,10,11] demonstrating extreme robustness (self-healing) of the filaments in reconstructing their intensity after encountering microscopic obstacles.In most of the studies reported so far filamentation was seeded using laser beams with Gaussian transverse profiles. Having in mind the GB nature of filaments, the possibility of directly launching a powerful Bessel beam into the material and thus circumventing the internal transformation from Gaussian toward GB beam, is intriguing. The internal transformation is governed by the materials' nonlinear response, which may limit the obtainable peak intensity of the GB beam. An external GB beam (e.g., generated using an axicon) may have power sufficient for inducing and sustaining extensive damage along its entire propagation path. The possibility to fabricate extended lines in transparent solids almost instantaneously is beneficial for laser microfabrication. Here we show ...

Periodic femtosecond filamentation in birefringent media

“…Longitudinal periodicity of different nature has been observed earlier in femtosecond filaments in isotropic media [5][6][7][8][9] in tight focusing conditions (NA > 0.3). In most cases, such a periodicity is associated with the…”

Hard X-ray generation using femtosecond irradiation of PbO glass

“…However, the self-focusing limited the achievable pulse irradiance/intensity in the case of back-side irradiation. Since the pulse power was larger than the threshold of self-focusing (typically, 1-3 MW for silicate glasses), the back-side irradiation resulted in a moving focus [35], which propagated in a manner similar to that of a Bessel-Gauss beam experiencing self-focusing [36].…”

Dinámica no lineal de haces ópticos de Airy y de Bessel en medios Kerr con absorción no lineal

“…En el caso de NBB fundamentales (sin vórtice), la inestabilidad radial parece ser la dominante ya que no se ha observado descomposición azimutal en los experimentos y simulaciones (Porras et al 2004;Polesana et al 2006;Gaizauskas et al 2006;Polesana et al 2008;Couairon et al 2013), particularmente en condiciones de introducción suave (Polesana et al 2007). El análisis lineal de estabilidad frente a pequeñas perturbaciones radiales ha sido realizado numéricamente para valores típicos del NBB en las referencias (Porras et al 2004;Polesana et al 2007).…”

“…En la primera disposición, el BB se introduce en el medio cuando ya está formado (Gadonas et al 2001;Pyragaite et al 2005;Polesana et al 2005;Gaizauskas et al 2006;Polesana et al 2006;Polesana et al 2007; Porras y Ruiz-Jiménez 2014), por ejemplo, el BB ideal en cualquier plano transversal, como se vio en la sección 3.3 del capítulo 3, o el BB apodizado que se forma en el foco de un axicón, situado a la mitad de la llamada zona de Bessel. Esta es la llamada introducción "abrupta" en el medio, ilustrada en la parte superior de la figura 4.1.…”

“…Esta es la llamada introducción "abrupta" en el medio, ilustrada en la parte superior de la figura 4.1. Excepto en el caso de que la absorción no lineal domine inicialmente la dinámica (Polesana et al 2005;Polesana et al 2006; Porras y Ruiz-Jiménez 2014), la no linealidad Kerr induce en este caso inestabilidades temporales y espaciales grandes (Gaizauskas et al 2006;Polesana et al 2007). Esta configuración ha sido también estudiada en relación a los haces de Airy en la subsección 2.7.1 del capítulo 2, donde también daba lugar a inestabilidades.…”