Femtosecond filament induced birefringence in argon and in air: Ultrafast refractive index change
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چکیده
منابع مشابه
Nanoindentation and birefringence measurements on fused silica specimen exposed to low-energy femtosecond pulses.
Femtosecond laser pulses used in a regime below the ablation threshold have two noticeable effects on Fused Silica (a-SiO2): they locally increase the material refractive index and modify its HF etching selectivity. The nature of the structural changes induced by femtosecond laser pulses in fused silica is not fully understood. In this paper, we report on nanoindentation and birefringence measu...
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Recently, we showed that femtosecond laser induced “nanogratings” consist of thin regions with a low refractive index (Δn = −0.15), due to the formation of nanoporous silica surrounded by regions with a positive index change. In this paper, we investigate a wide range of laser parameters to achieve very high retardance within a single layer; as much as 350 nm at λ = 546 nm but also to minimize ...
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The axial dependence of femtosecond filamentation in air is measured under conditions of varying laser pulsewidth, energy, and focusing f-number. Filaments are characterized by the ultrafast z-dependent absorption of energy from the laser pulse and diagnosed by measuring the local single cycle acoustic wave generated. Results are compared to 2D+ 1 simulations of pulse propagation, whose results...
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We present a practical method to determine femtosecond laser induced refractive index changes in transparent materials. Based on an iterative Fourier transform algorithm, this technique spatially resolves the refractive index of complex structures by combining the dimensions of the modified region with the corresponding phase change extracted from far-field intensity measurements. This approach...
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Ultrafast laser-induced refractive index changes in a-SiO2 consist, depending on the irradiation conditions, of either positive variations, voids, or regular nanoscale patterns, each of these underlying specific structural transformations. These allow for obtaining a large palette of optical functions ranging from low loss guiding to anisotropic scattering. While briefly reviewing the excitatio...
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