119 research outputs found
Self-organized pattern formation in laser-induced multiphoton ionization
We use finite-difference time-domain modelling to investigate plasma
generation induced by multi-photon absorption of intense laser light in
dielectrics with tiny inhomogenities. Plasma generation is found to be strongly
amplified around nanometer-sized inhomogeneities as present in glasses. Each
inhomogeneity acts as the seed of a plasma structure growing against the
direction of light propagation. Plasma structures originating from randomly
distributed inhomogeneities are found to interact strongly and to organize in
regularly spaced planes oriented perpendicularly to the laser polarization. We
discuss similarities between our results and nanogratings in fused silica
written by laser beams with spatially homogeneous as well as radial and
azimuthal polarization.Comment: 8 pages, 9 figure
Generation and subwavelength focusing of longitudinal magnetic fields in a metallized fiber tip
We demonstrate experimentally and numerically that in fiber tips as they are
used in NSOMs azimuthally polarized electrical fields
(|E|/|E| 55% 5% for
1.4\mu m tip aperture diameter and \lambda = 1550nm), respectively
subwavelength confined (FWHM 450nm \lambda/3.5)
magnetic fields, are generated for a certain tip aperture diameter (d = 1.4\mu
m). We attribute the generation of this field distribution in metal-coated
fiber tips to symmetry breaking in the bend and subsequent plasmonic mode
filtering in the truncated conical taper.Comment: 11 pages, 6 figure
Photon propagation in a discrete fiber network: An interplay of coherence and losses
We study light propagation in a photonic system that shows stepwise evolution
in a discretized environment. It resembles a discrete-time version of photonic
waveguide arrays or quantum walks. By introducing controlled photon losses to
our experimental setup, we observe unexpected effects like sub-exponential
energy decay and formation of complex fractal patterns. This demonstrates that
the interplay of linear losses, discreteness and energy gradients leads to
genuinely new coherent phenomena in classical and quantum optical experiments.
Moreover, the influence of decoherence is investigated.Comment: To appear in PR
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