The polarization state (or relative phase) of each VCSEL in an injection-locked array can serve as an analogue Ising bit. We propose use of a spatial light modulator, along with associated collimation optics, to control the interaction strengths of the Ising Hamiltonian. The advantage of this approach is that it affectively allows all-to-all coupling between the Ising bits in a controllable way. The Ising computation would be particularly speedy since the feedback path is all-optical.
KEYWORDS: Device simulation, 3D modeling, Sensors, Defect detection, Finite element methods, Electromagnetism, Resistance, Capacitance, Systems modeling, Nondestructive evaluation, Free space
Electrical resonance based eddy current methods are being investigated and developed for the detection of sub-millimeter surface defects in low conductivity material such as superalloy in aircraft. The probe has high sensitivity due to the noise elimination by evaluate the relative resonance shift on the impedance change cause by material properties variance. This method has reported analytically with experimental validation recently. In this paper, the detecting system includes the coil sensor and the coaxial connection is modelled using full wave electromagnetic simulation with integration of the circuit co-simulator. The finite element simulation is to study the probe behavior while the circuit model simulator is used to investigate the influence of the component such as capacitance and resistance in the detection system. With our model, further investigation on the sensitivity of the detection system due to the variation of sensor parameters, such as ferrite core and liftoff as well as and capacitance and effective resistance from the electronic component, is performed. This study not only contributes to the optimization and sensitivity enhancement of the detecting system, but also provide accurate detection of submillimeter defect.
A fast crack profile reconstitution method is developed using eddy current probing scheme. The technique employed genetic algorithm (GA) optimization together with boundary element method (BEM) to evaluate the shape of the cracks that are described by using the Lagrange polynomial (LP). In doing so, the shape of the open cracks could be obtained. Compared to the pixel-based description of the cracks, the LP description could significantly reduce the number of the unknowns, and this increases the efficiency of the global searching by the GA. This technique has greatly improved the efficiency of the inversion solver. Numerical tests are shown to validate the interests.
Chirality effect has been reported from the interaction of light with chiral plasmonic
nanostructures. Such nanostructure enhances the chirality response of the chiral
molecules and provides a good platform for biochemical sensing. The ability to detect
chiral molecules has been a long term goal of biologists and chemist because chirality
is inherent in macromolecules such as proteins and DNA in human body. One of the
challenging problems is manipulation of the CD spectrum. Here, we investigate the
switchable chiral effects of subwavelength nanostructures array with the unit cell
makes up of double-layered nanostrips in four-fold rotationally symmetric
arrangement. The switchable chirality effect has observed in both plasmonic and
Bloch modes when the mutual angle between the first layer and second layer rotates
with respect to each other. The magnitude of chirality changes from positive to
negative when the mutual angle rotates from 0o to 90o. In the order hand, the
nanostructures change from right-handed to left-handed structures without altering the
polarization of incident light, or vice versa, upon the mutual rotation angles. Thus, by
manipulating the mutual rotation angle, the handedness of the nanostructure will
switch and cause the reversal of the outgoing light.
In this paper, we design layered composite meta-structures to investigate its’ effect on the optical activity and circular
dichroism (CD). The layered composite meta-structures consist of thin gammadion nanostructure with thickness λ/10,
where λ is the incident wavelength. The layered meta-structures are alternate between a dielectric and gold (AU)
material. Each layered composite meta-gammadion is arranged together in an array of pitch 700 nm. In the first case, 3
layers of meta-gammadion, with metal-insulator-metal (MIM) and insulator-metal-insulator (IMI) configuration are
simulated with material properties from optical hand book. There are 3 modes in the CD spectrum, which can be
characterized into Bloch CD mode and hybrid CD modes. Compared with the CD spectrum of whole structure of
gammadion in gold with same total height, the CD of the MIM layered composite are larger. When the number layer
increase to 5, it is observed that the CD is reduced by 30% and there is a red shift in the Bloch CD mode and a slight blue
shift in the hybrid CD modes. By further increasing the number of layers to 7, we observed further CD increment and
larger wavelength shift in the CD modes. The layered composite meta-gammadion is fabricated using template stripping
method. Experimental results also show excellent agreement with the simulation results for CD and wavelength shift. We
submerge the layered meta-gammadion into a solution of chiral molecules. The CD spectrum of the meta-gammadion
shows a larger wavelength shift compared to pure metal structures. This indicate a more sensitive and robust detection of
chiral molecules.
In this paper, we rotate an array of asymmetrical double layer of 4-strips windmill structure to investigate its effect on
the chirality and sensitivity detection of biomolecular structures. The structure is made up of silver material with 300nm
pitch and 10nm separation between layers. The spectrum shows two resonance modes on 600THz and 900THz with
linear polarized light normally incident on the structure. We investigate the CD by rotating one of the layers with respect
to the horizontal axis of the other layer by the angle θ. It is observed that the CD spectra at different angles are different.
The rotation resulted in larger wavelength shift of the CD spectra. In addition, the CD also increases with the rotating
angle given a larger absorption difference between the left and right handed circular polarized light.
In this paper, the effect of tapered asymmetrical gammadion on the optical rotational properties and sensitivity detection
of biomolecular structures is presented. The asymmetrical structure is made up of gold material on a glass structure and
immersed in water. The chirality of the un-rotated array is first determined by measuring the circular dichroism (CD)
spectrum. Three modes, arising from Bloch periodic theory and surface resonance mode are observed. Then each
asymmetrical gammadion structure is tapered at the arms. Tapering fraction, which define the ratio of tapered end to the untapered end is used for defining the new design. The designs are then fabricated using e-beam lithography and tested using the polarimeter for CD spectra. The spectra show that the three CD modes changes in degree amplitude and wavelength, especially for smaller tapering fractions.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.