132 research outputs found
The photonic wheel: demonstration of a state of light with purely transverse angular momentum
The concept of angular momentum is ubiquitous to many areas of physics. In
classical mechanics, a system may possess an angular momentum which can be
either transverse (e.g., in a spinning wheel) or longitudinal (e.g., for a
fluidic vortex) to the direction of motion. Photons, however, are well-known to
exhibit intrinsic angular momentum which is longitudinal only: the spin angular
momentum defining the beam polarization and the orbital angular momentum
associated with a spiraling phase front. Here we show that it is possible to
generate a novel state of light that contains purely transverse angular
momentum, the analogue of a spinning mechanical wheel. We use an optical
nano-probing technique to experimentally demonstrate its occurrence in our
setup. Such a state of light can provide additional rotational degree of
freedom in optical tweezers and optical manipulation.Comment: 15 pages including SO
Geometric spin Hall effect of light in tightly focused polarization tailored light beams
Recently, it was shown that a non-zero transverse angular momentum manifests
itself in a polarization dependent intensity shift of the barycenter of a
paraxial light beam [A. Aiello et al., Phys. Rev. Lett. 103, 100401 (2009)].
The underlying effect is phenomenologically similar to the spin Hall effect of
light, but does not depend on the specific light-matter interaction and can be
interpreted as a purely geometric effect. Thus, it was named the geometric spin
Hall effect of light. Here, we experimentally investigate the appearance of
this effect in tightly focused vector-beams. We use an experimental
nano-probing technique in combination with a reconstruction algorithm to verify
the relative shifts of the components of the electric energy density in the
focal plane, which are linked to the intensity shift. By that, we
experimentally demonstrate the geometric spin Hall effect of light in a focused
light beam.Comment: 8 pages, 5 figure
Prospect for detecting squeezed states of light created by a single atom in free space
We discuss the possibilities of studying in detail the dynamics of
spontaneous emission of a single photon by a single atom and measuring the
transient degree of squeezing by means of full solid angle fluorescence
detection.Comment: Accepted for publication in Optics Communication
Ultra-high field enhancing in Split Ring Resonators by azimuthally polarized excitation
We study the field enhancement and resonance frequencies in split-ring
resonators (SRR) illuminated by azimuthally polarized light. We find that
compared to linearly polarized illumination, the azimuthally polarized
illumination increase the intensity enhancement by more than an order of
magnitude. We attribute the increase in the intensity enhancement to the
improved overlap between the SRR geometry and the direction of the electric
field vector in each point. In addition, we present and explore a method to
tune the resonance frequency of the SRR (for azimuthal polarization) by
introducing more gaps to the structure. This approach allows for simple and
straightforward tuning of the resonance frequency with small impact on the
intensity enhancement. The impact of the design parameters on the intensity
enhancement under azimuthally polarized illumination is also studied in
details, exhibiting clear differences to the case of linear polarized
illumination.Comment: To be published in Optics Expres
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.
The photonic wheel - demonstration of a state of light with purely transverse angular momentum
In classical mechanics, a system may possess angular momentum which can be either transverse (e.g. in a spinning wheel) or longitudinal(e.g. for a spiraling seed falling from a tree) with respect to the direction of motion. However, for light, a typical massless wave system,the situation is less versatile. Photons are well-known to exhibit intrinsic angular momentum which is longitudinal only: the spin angularmomentum defining the polarization and the orbital angular momentum associated with a spiraling phase front. Here we show that itis possible to generate a novel state of the light field that contains purely transverse angular momentum, the analogue of a spinningmechanical wheel. We realize this state by tight focusing of a polarization tailored light beam and measure it using an optical nano-probingtechnique. Such a novel state of the light field can find applications in optical tweezers and spanners where it allows for additionalrotational degree of freedom not achievable in single-beam configurations so far
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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