90 research outputs found
Resonances On-Demand for Plasmonic Nano-Particles
A method for designing plasmonic particles with desired resonance spectra is
presented. The method is based on repetitive perturbations of an initial
particle shape while calculating the eigenvalues of the various quasistatic
resonances. The method is rigorously proved, assuring a solution exists for any
required spectral resonance location. Resonances spanning the visible and the
near-infrared regimes, as designed by our method, are verified using
finite-difference time-domain simulations. A novel family of particles with
collocated dipole-quadrupole resonances is designed, demonstrating the unique
power of the method. Such on-demand engineering enables strict realization of
nano-antennas and metamaterials for various applications requiring specific
spectral functions
Femtogram Doubly Clamped Nanomechanical Resonators Embedded in a High-Q Two-Dimensional Photonic Crystal Nanocavity
We demonstrate a new optomechanical device system which allows highly
efficient transduction of femtogram nanobeam resonators. Doubly clamped
nanomechanical resonators with mass as small as 25 fg are embedded in a
high-finesse two-dimensional photonic crystal nanocavity. Optical transduction
of the fundamental flexural mode around 1 GHz was performed at room temperature
and ambient conditions, with an observed displacement sensitivity of 0.94
fm/Hz^(1/2). Comparison of measurements from symmetric and asymmetric
double-beam devices reveals hybridization of the mechanical modes where the
structural symmetry is shown to be the key to obtain a high mechanical quality
factor. Our novel configuration opens the way for a new category of
"NEMS-in-cavity" devices based on optomechanical interaction at the nanoscale.Comment: Nano Lett. 201
Outlook for inverse design in nanophotonics
Recent advancements in computational inverse design have begun to reshape the
landscape of structures and techniques available to nanophotonics. Here, we
outline a cross section of key developments at the intersection of these two
fields: moving from a recap of foundational results to motivation of emerging
applications in nonlinear, topological, near-field and on-chip optics.Comment: 13 pages, 6 figure
Joint Inversion of DC Resistivity and Magnetic Data, Constrained by Cross Gradients, Compactness and Depth Weighting
In this paper we perform a 2-D joint inversion of DC resistivity and magnetic data, constrained by cross-gradients. Inspired by methods developed for potential fields, we introduce into both the separate and joint inversion algorithms also compactness and depth weighting functions, under the form of a model weighting-function. These constraints, usually not considered for DC resistivity inversion, reveal to be decisive for its joint inversion with magnetic data. A linear approximated forward problem of the resistivity is used for the joint inversion so that both the resistivity and magnetic problems are expressed as a linear integral equation under the form of a Fredholm integral of 1st kind. To examine the feasibility of the joint inversion algorithm, we first test the method with two synthetic cases: a thick dyke in a two-layered medium and a cavity located above a conductor. A third synthetic case involves a multisource model. The results are encouraging, revealing that the cross-gradient constraint is an effective tool to improve the separate inversions of DC resistivity and magnetic data. The joint inversion algorithm is also applied to data in the archeological area of the old Pompeii city, nearby Naples. Comparing the results of joint and separate inversions, we obtain a significant improvement in the interpretation of both kind of data in terms of buried walls of an ancient roman villa. In all the studied cases, the cross-gradient constraint appears to be a key-diagnostic tool to assess whether actual coherence is gained among DC resistivity and magnetic susceptibility models
Gravity and Magnetic Processing and Inversion Over the Mahallat Geothermal System Using Open Source Resources in Python
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