77 research outputs found
Waveguide properties of single subwavelength holes demonstrated with radially and azimuthally polarized light
We investigate the transmission of focused beams through single subwavelength
holes in a silver film. We use radially and azimuthally polarized light,
respectively, to excite higher order waveguide modes as well as to match the
radial symmetry of the aperture geometry. Remarkably, the transmission
properties can be described by a classical waveguide model even for thicknesses
of the silver film as thin as a quarter of a wavelength
The focus of light - linear polarization breaks the rotational symmetry of the focal spot
We experimentally demonstrate for the first time that a linearly polarized
beam is focussed to an asymmetric spot when using a high-numerical aperture
focussing system. This asymmetry was predicted by Richards and Wolf
[Proc.R.Soc.London A, 253, 358 (1959)] and can only be measured when a
polarization insensitive sensor is placed in the focal region. We used a
specially modified photodiode in a knife edge type set up to obtain highly
resolved images of the total electric energy density distribution at the focus.
The results are in good agreement with the predictions of a vectorial focussing
theory.Comment: to be published in "Journal of Modern Optics
On the experimental investigation of the electric and magnetic response of a single nano-structure
We demonstrate an experimental method to separately test the optical response
of a single sub-wavelength nano-structure to tailored electric and magnetic
field distributions in the optical domain. For this purpose a highly focused
y-polarized TEM10-mode is used which exhibits spatially separated longitudinal
magnetic and transverse electric field patterns. By displacing a single
sub-wavelength nano-structure, namely a single split-ring resonator (SRR), in
the focal plane, different coupling scenarios can be achieved. It is shown
experimentally that the single split-ring resonator tested here responds
dominantly as an electric dipole. A much smaller but yet statistically
significant magnetic dipole contribution is also measured by investigating the
interaction of a single SRR with a magnetic field component perpendicular to
the SRR plane (which is equivalent to the curl of the electric field) as well
as by analyzing the intensity and polarization distribution of the scattered
light with high spatial resolution. The developed experimental setup as well as
the measurement techniques presented in this paper are a versatile tool to
investigate the optical properties of single sub-wavelength nano-structures.Comment: 19 pages, 9 figures, accepted by Optics Expres
Direct High-Power Laser Acceleration of Ions for Medical Applications
Theoretical investigations show that linearly and radially polarized
multiterawatt and petawatt laser beams, focused to subwavelength waist radii,
can directly accelerate protons and carbon nuclei, over micron-size distances,
to the energies required for hadron cancer therapy. Ions accelerated by
radially polarized lasers have generally a more favorable energy spread than
those accelerated by linearly polarized lasers of the same intensity.Comment: 4 pages, 5 figure
Ultrashort Focused Electromagnetic Pulses
In this article we present a closed analytical description for few-cycle,
focused electromagnetic pulses of arbitrary duration and carrier-envelope-phase
(CEP). Because of the vectorial character of light, not all thinkable
one-dimensional (1D) shapes for the transverse electric field or vector
potential can be realized as finite energy three-dimensional (3D) structures.
We cope with this problem by using a second potential, which is defined as a
primitive to the vector potential. This allows to construct fully consistent 3D
wave-packet solutions for the Maxwell equations, given a solution of the scalar
wave equation. The wave equation is solved for ultrashort, Gaussian and related
pulses in paraxial approximation. The solution is given in a closed and
numerically convenient form, based on the complex error function. All results
undergo thorough numerical testing, validating their correctness and accuracy.
A reliable and accurate representation of few-cycle pulses is e.g. crucial for
analytical and numerical theory of vacuum particle acceleration.Comment: 8 pages, 5 figure
Strong extinction of a far-field laser beam by a single quantum dot
Through the utilization of index-matched GaAs immersion lens techniques we
demonstrate a record extinction (12%) of a far-field focused laser by a single
InAs/GaAs quantum dot. This contrast level enables us to report for the first
time resonant laser transmission spectroscopy on a single InAs/GaAs quantum dot
without the need for phase-sensitive lock-in detection
Generation of a wave packet tailored to efficient free space excitation of a single atom
We demonstrate the generation of an optical dipole wave suitable for the
process of efficiently coupling single quanta of light and matter in free
space. We employ a parabolic mirror for the conversion of a transverse beam
mode to a focused dipole wave and show the required spatial and temporal
shaping of the mode incident onto the mirror. The results include a proof of
principle correction of the parabolic mirror's aberrations. For the application
of exciting an atom with a single photon pulse we demonstrate the creation of a
suitable temporal pulse envelope. We infer coupling strengths of 89% and
success probabilities of up to 87% for the application of exciting a single
atom for the current experimental parameters.Comment: to be published in Europ. Phys. J.
Design of a mode converter for efficient light-atom coupling in free space
In this article, we describe how to develop a mode converter that transforms
a plane electromagnetic wave into an inward moving dipole wave. The latter one
is intended to bring a single atom or ion from its ground state to its excited
state by absorption of a single photon wave packet with near-100% efficiency.Comment: RevTex4, 3 figures, revised version, accepted for publication at
Appl. Phys.
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