11,861 research outputs found
Dual regimes of ion migration in high repetition rate femtosecond laser inscribed waveguides
Ion migration in high repetition rate femtosecond laser inscribed waveguides
is currently being reported in different optical glasses. For the first time we
discuss and experimentally demonstrate the presence of two regimes of ion
migration found in laser written waveguides. Regime-I, corresponds to the
initial waveguide formation mainly via light element migration (in our case
atomic weight < 31u), whereas regime-II majorly corresponds to the movement of
heavy elements. This behavior brings attention to a problem which has never
been analyzed before and that affects laser written active waveguides in which
active ions migrate changing their local spectroscopic properties. The
migration of active ions may in fact detune the pre-designed optimal values of
active photonic devices. This paper experimentally evidences this problem and
provides solutions to avert it.Comment: 4 pages, 5 figure
Investigation of ultrafast laser photonic material interactions: challenges for directly written glass photonics
Currently, direct-write waveguide fabrication is probably the most widely
studied application of femtosecond laser micromachining in transparent
dielectrics. Devices such as buried waveguides, power splitters, couplers,
gratings and optical amplifiers have all been demonstrated. Waveguide
properties depend critically on the sample material properties and writing
laser characteristics. In this paper we discuss the challenges facing
researchers using the femtosecond laser direct-write technique with specific
emphasis being placed on the suitability of fused silica and phosphate glass as
device hosts for different applications.Comment: 11 pages, 87 references, 11 figures. Article in revie
Nanoscale Processing by Adaptive Laser Pulses
We theoretically demonstrate that atomically-precise ``nanoscale processing"
can be reproducibly performed by adaptive laser pulses. We present the new
approach on the controlled welding of crossed carbon nanotubes, giving various
metastable junctions of interest. Adaptive laser pulses could be also used in
preparation of other hybrid nanostructures.Comment: 4 pages, 4 Postscript figure
Four-dimensional light shaping: manipulating ultrafast spatio-temporal foci in space and time
Spectral dispersion of ultrashort pulses allows simultaneous focusing of
light in both space and time creating so-called spatio-temporal foci. Such
space-time coupling may be combined with existing holographic techniques to
give a further dimension of control when generating focal light fields. It is
shown that a phase-only hologram placed in the pupil plane of an objective and
illuminated by a spatially chirped ultrashort pulse can be used to generate
three dimensional arrays of spatio-temporally focused spots. Exploiting the
pulse front tilt generated at focus when applying simultaneous spatial and
temporal focusing (SSTF), it is possible to overlap neighbouring foci in time
to create a smooth intensity distribution. The resulting light field displays a
high level of axial confinement, with experimental demonstrations given through
two-photon microscopy and non-linear laser fabrication of glass
Rapid assessment of nonlinear optical propagation effects in dielectrics
Ultrafast laser processing applications need fast approaches to assess the nonlinear propagation of the laser beam in order to predict the optimal range of processing parameters in a wide variety of cases. We develop here a method based on the simple monitoring of the nonlinear beam shaping against numerical prediction. The numerical code solves the nonlinear Schrödinger equation with nonlinear absorption under simplified conditions by employing a state-of-the art computationally efficient approach. By comparing with experimental results we can rapidly estimate the nonlinear refractive index and nonlinear absorption coefficients of the material. The validity of this approach has been tested in a variety of experiments where nonlinearities play a key role, like spatial soliton shaping or fs-laser waveguide writing. The approach provides excellent results for propagated power densities for which free carrier generation effects can be neglected. Above such a threshold, the peculiarities of the nonlinear propagation of elliptical beams enable acquiring an instantaneous picture of the deposition of energy inside the material realistic enough to estimate the effective nonlinear refractive index and nonlinear absorption coefficients that can be used for predicting the spatial distribution of energy deposition inside the material and controlling the beam in the writing process
Rapid assessment of nonlinear optical propagation effects in dielectrics
8 págs.; 6 figs.; Open Access funded by Creative Commons Atribution Licence 4.0Ultrafast laser processing applications need fast approaches to assess the nonlinear propagation of the laser beam in order to predict the optimal range of processing parameters in a wide variety of cases. We develop here a method based on the simple monitoring of the nonlinear beam shaping against numerical prediction. The numerical code solves the nonlinear Schrodinger equation with nonlinear absorption under simplified conditions by employing a state-of-the art computationally efficient approach. By comparing with experimental results we can rapidly estimate the nonlinear refractive index and nonlinear absorption coefficients of the material. The validity of this approach has been tested in a variety of experiments where nonlinearities play a key role, like spatial soliton shaping or fs-laser waveguide writing. The approach provides excellent results for propagated power densities for which free carrier generation effects can be neglected. Above such a threshold, the peculiarities of the nonlinear propagation of elliptical beams enable acquiring an instantaneous picture of the deposition of energy inside the material realistic enough to estimate the effective nonlinear refractive index and nonlinear absorption coefficients that can be used for predicting the spatial distribution of energy deposition inside the material and controlling the beam in the writing process.This work has been partly funded by MINECO TEC2011-22422 project. J. de H.
acknowledges funding from the JAE CSIC Program (pre-doctoral fellowship co-funded by
the European Social Fund). A.P. acknowledges support from the People Program (Marie
Curie Actions) Incoming International Fellowship (CHRONOS) under REA grant
agreement nu [327627].Peer Reviewe
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