X-waves Generated at Second Harmonic

The process of optical frequency doubling can lead, in the undepleted regime, to the generation of a X-wave envelope with group velocity locked to the pump beam. Its parameters and its angular spectrum, are directly related to the zero- and first-order dispersive features of the nonlinear process. This constitutes a novel mechanism for spatio-temporal localization of light.Comment: 11 pages, 1 figure, revised version submitted to Optics Letter

General quasi-non-spreading linear three-dimensional wave-packets

We introduce a general approach for generation of sets of three-dimensional quasi-non-spreading wavepackets propagating in linear media, also referred to as linear light bullets. The spectrum of rigorously non-spreading wavepackets in media with anomalous group velocity dispersion is localized on the surface of a sphere, thus drastically restricting the possible wavepacket shapes. However, broadening slightly the spectrum affords the generation of a large variety of quasi-non-spreading distributions featuring complex topologies and shapes in space and time that are of interest in different areas, such as biophysics or nanosurgery. Here we discuss the method and show several illustrative examples of its potential.Comment: 3 pages, 4 figures, to appear in Optics Letter

X-wave mediated instability of plane waves in Kerr media

Plane waves in Kerr media spontaneously generate paraxial X-waves (i.e. non-dispersive and non-diffractive pulsed beams) that get amplified along propagation. This effect can be considered a form of conical emission (i.e. spatio-temporal modulational instability), and can be used as a key for the interpretation of the out of axis energy emission in the splitting process of focused pulses in normally dispersive materials. A new class of spatio-temporal localized wave patterns is identified. X-waves instability, and nonlinear X-waves, are also expected in periodical Bose condensed gases.Comment: 4 pages, 6 figure

Lidchirurgie bei orbitotemporaler Neurofibromatose

Neurofibromatose Typ 1 (NF 1) ist eine der häufigsten genetischen Krankheiten, die autosomal-dominant vererbt wird. Die Inzidenz wird in der Literatur von 1 : 3000 bis 1 : 4000 beschrieben [1]. Diese Multiorgankrankheit macht sich überwiegend an der Haut und im Nervensystem bemerkbar. Auch Neurofibromatose Typ 2 ist eine Phakomatose und wird autosomal-dominant vererbt, ist aber etwa 10-mal seltener als NF 1 [2]. Neurofibromatose Typ 1 hat viele okuläre Manifestationen wie Lisch-Knötchen der Iris und Anomalien der Choroidea [3]. Etwa 30% der Patienten mit Optikusgliomen haben NF 1 [4]. Mit 4 Fallbeispielen wollen wir die wichtigsten okuloplastischen Aspekte bei NF-1-Patienten vorstellen. Insgesamt wurden in unserer Klinik, die 1,3 Mill. Menschen bedient, 17 Patienten mit periokulären Neurofibromen in 25 Jahren behandelt