494 research outputs found
Observation of the skin-depth effect on the Casimir force between metallic surfaces
We have performed comparative measurements of the Casimir force between a
metallic plate and a transparent sphere coated with metallic films of different
thicknesses. We have observed that, if the thickness of the coating is less
than the skin-depth of the electromagnetic modes that mostly contribute to the
interaction, the force is significantly smaller than that measured with a thick
bulk-like film. Our results provide the first direct evidence of the skin-depth
effect on the Casimir force between metallic surfaces.Comment: submitted for publication on Dec. 10, 2004. 3 figure
Lateral Chirality-sorting Optical Spin Forces in Evanescent Fields
The transverse component of the spin angular momentum of evanescent waves
gives rise to lateral optical forces on chiral particles, which have the
unusual property of acting in a direction in which there is neither a field
gradient nor wave propagation. As their direction and strength depends on the
chiral polarizability of the particle, they act as chirality-sorting and may
offer a mechanism for passive chirality spectroscopy. The absolute strength of
the forces also substantially exceeds that of other recently predicted sideways
optical forces, such that they may more readily offer an experimental
confirmation of the phenomenon.Comment: 7 pages, 2 Figure
New Challenges and Directions in Casimir Force Experiments
This article is divided in three sections. In the first section we briefly
review some high precision experiments on the Casimir force, underlying an
important aspect of the analysis of the data. In the second section we discuss
our recent results in the measurement of the Casimir force using non-trivial
materials. In the third section we present some original ideas for experiments
on new phenomena related to the Casimir effects.Comment: 6 pages, invited contribution to the 6th Workshop on Quantum Field
Theory under the Influence of External Conditions (QFEXT03), Norman,
Oklahoma, September 15-19, 200
Absolute Position Total Internal Reflection Microscopy with an Optical Tweezer
A non-invasive, in-situ calibration method for Total Internal Reflection
Microscopy (TIRM) based on optical tweezing is presented which greatly expands
the capabilities of this technique. We show that by making only simple
modifications to the basic TIRM sensing setup and procedure, a probe particle's
absolute position relative to a dielectric interface may be known with better
than 10 nm precision out to a distance greater than 1 m from the surface.
This represents an approximate 10x improvement in error and 3x improvement in
measurement range over conventional TIRM methods. The technique's advantage is
in the direct measurement of the probe particle's scattering intensity vs.
height profile in-situ, rather than relying on calculations or inexact system
analogs for calibration. To demonstrate the improved versatility of the TIRM
method in terms of tunability, precision, and range, we show our results for
the hindered near-wall diffusion coefficient for a spherical dielectric
particle.Comment: 10 pages. Submitted for peer review 8/20/201
Topology Optimized Multi-layered Meta-optics
We propose a general topology optimization framework for metasurface inverse
design that can automatically discover highly complex multi-layered
meta-structures with increased functionalities. In particular, we present
topology-optimized multi-layered geometries exhibiting angular phase control,
including a single-piece nanophotonic metalens with angular aberration
correction as well as an angle-convergent metalens that focuses light onto the
same focal spot regardless of the angle of incidence
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