504 research outputs found
Etalon Array Reconstructive Spectrometry.
Compact spectrometers are crucial in areas where size and weight may need to be minimized. These types of spectrometers often contain no moving parts, which makes for an instrument that can be highly durable. With the recent proliferation in low-cost and high-resolution cameras, camera-based spectrometry methods have the potential to make portable spectrometers small, ubiquitous, and cheap. Here, we demonstrate a novel method for compact spectrometry that uses an array of etalons to perform spectral encoding, and uses a reconstruction algorithm to recover the incident spectrum. This spectrometer has the unique capability for both high resolution and a large working bandwidth without sacrificing sensitivity, and we anticipate that its simplicity makes it an excellent candidate whenever a compact, robust, and flexible spectrometry solution is needed
Direct observation of plasmonic index ellipsoids on a deep-subwavelength metallic grating
We constructed a metallic grating on a deep-subwavelength scale and tested its plasmonic features in visible frequencies. The deep-subwavelength metallic grating effectively acts as an anisotropic homogeneous uniaxial form-birefringent metal, exhibiting different optical responses for polarizations along different optical axes. Therefore, this form-birefringent metal supports anisotropic surface plasmon polaritons that are characterized by directly imaging the generated plasmonic index ellipsoids in reciprocal space. The observed plasmonic index ellipsoids also show a rainbow effect, where different colors are dispersively distributed in reciprocal space
Theory of optical imaging beyond the diffraction limit with a far-field superlens
Recent theoretical and experimental studies have shown that imaging with
resolution well beyond the diffraction limit can be obtained with so-called
superlenses. Images formed by such superlenses are, however, in the near field
only, or a fraction of wavelength away from the lens. In this paper, we propose
a far-field superlens (FSL) device which is composed of a planar superlens with
periodical corrugation. We show in theory that when an object is placed in
close proximity of such a FSL, a unique image can be formed in far-field. As an
example, we demonstrate numerically that images of 40 nm lines with a 30 nm gap
can be obtained from far-field data with properly designed FSL working at 376nm
wavelength.Comment: 6 pages, 3 figure
Isogeometric FEM-BEM coupled structural-acoustic analysis of shells using subdivision surfaces
We introduce a coupled finite and boundary element formulation for acoustic
scattering analysis over thin shell structures. A triangular Loop subdivision
surface discretisation is used for both geometry and analysis fields. The
Kirchhoff-Love shell equation is discretised with the finite element method and
the Helmholtz equation for the acoustic field with the boundary element method.
The use of the boundary element formulation allows the elegant handling of
infinite domains and precludes the need for volumetric meshing. In the present
work the subdivision control meshes for the shell displacements and the
acoustic pressures have the same resolution. The corresponding smooth
subdivision basis functions have the continuity property required for the
Kirchhoff-Love formulation and are highly efficient for the acoustic field
computations. We validate the proposed isogeometric formulation through a
closed-form solution of acoustic scattering over a thin shell sphere.
Furthermore, we demonstrate the ability of the proposed approach to handle
complex geometries with arbitrary topology that provides an integrated
isogeometric design and analysis workflow for coupled structural-acoustic
analysis of shells
Untrained, physics-informed neural networks for structured illumination microscopy
In recent years there has been great interest in using deep neural networks
(DNN) for super-resolution image reconstruction including for structured
illumination microscopy (SIM). While these methods have shown very promising
results, they all rely on data-driven, supervised training strategies that need
a large number of ground truth images, which is experimentally difficult to
realize. For SIM imaging, there exists a need for a flexible, general, and
open-source reconstruction method that can be readily adapted to different
forms of structured illumination. We demonstrate that we can combine a deep
neural network with the forward model of the structured illumination process to
reconstruct sub-diffraction images without training data. The resulting
physics-informed neural network (PINN) can be optimized on a single set of
diffraction limited sub-images and thus doesn't require any training set. We
show with simulated and experimental data that this PINN can be applied to a
wide variety of SIM methods by simply changing the known illumination patterns
used in the loss function and can achieve resolution improvements that match
well with theoretical expectations.Comment: Preprint for journal submission. 21 Pages. 5 main text figures. 6
supplementary figure
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