Enhanced avionic sensing based on Wigner’s cusp anomalies

Typical sensors detect small perturbations by measuring their effects on a physical observable, using a linear response principle (LRP). It turns out that once LRP is abandoned, new opportunities emerge. A prominent example is resonant systems operating near Nth-order exceptional point degeneracies (EPDs) where a small perturbation ε ≪ 1 activates an inherent sublinear response ∼εN≫ε in resonant splitting. Here, we propose an alternative sublinear optomechanical sensing scheme that is rooted in Wigner’s cusp anomalies (WCAs), first discussed in the framework of nuclear reactions: a frequency-dependent square-root singularity of the differential scattering cross section around the energy threshold of a newly opened channel, which we use to amplify small perturbations. WCA hypersensitivity can be applied in a variety of sensing applications, besides optomechanical accelerometry discussed in this paper. Our WCA platforms are compact, do not require a judicious arrangement of active elements (unlike EPD platforms), and, if chosen, can be cavity free.

Elliptically polarized laser assisted elastic electron-hydrogen atom collision and differential scattering cross-section

In the present study, we have investigated scattering of an electron by hydrogen atoms in the presence of the elliptical polarized laser field. We have discussed the polarization effect of laser field on hydrogen atom and effect of the resulted polarized potential on differential scattering cross-section is studied. We assume the scattered electrons having kinetic energy (~3000 eV) and laser field of moderate field strength because it is permitted to treat the scattering process in first Born approximation and the scattering electron was described by Volkov wave function. We found that the differential scattering cross-section area increases with the increase of the kinetic energy of the incident electron and there is no effect of changing the value of polarizing angle on the differential cross-section with kinetic energy. We observed that differential scattering cross-section in elliptical polarization in the high energy region depends upon the laser intensity and the incident energy for a linearly polarized field.

Free Scattering Theory in Circularly Polarized Laser Field

<p class="Default">In the present study, we have investigated scattering of an electron by hydrogen atoms in the presence of the Circularly Polarized (CP) laser field. We have discussed the polarization effect of laser field on hydrogen atom and effect of the resulted polarized potential on differential scattering cross section is studied. We assumed the scattered electrons having kinetic energy 100 eV because it permitted to treat the scattering process in first order Born Approximation. The scattering electron was described by Volkov wave function. We found the differential scattering cross section decreases with the increase in scattering angle, for a fixed value of a laser parameters and kinetic energy of an incident electron. From this study we found that, the differential scattering cross section for the electric field perpendicular to the direction of momentum transfer depends on the elastic scattering amplitude. Finally, we concluded that the differential scattering cross section greatly depends upon the polarization of the laser field.</p><p><strong>Journal of Nepal Physical Society</strong><br />Volume 4, Issue 1, February 2017, Page: 78-87</p>

Analysis of Light Scattering Properties about Dent Nanoparticles upon Wafer

The light scattering properties of the dent nanoparticles upon wafers is discussed in this paper. Taking the advantage of the Bobbert-Vlieger (BV) theorem, the scattering model between wafer and dent nanoparticles is established. The scattering process is analyzed and the scattering coefficients are derived by using of the vector spherical harmonic function. The differential scattering cross section (DSCS) of the dent nanoparticles upon the wafer is calculated which is compared with the extended Mie method proved the validity of the method and the influences of the dent position, dent scale and scattering angle on the DSCS are analyzed numerically in details. The result is shown that the effect of the dielectric is smaller than the metal. Therefore, the material of the defect and the shape can be extracted by calculate the DSCS, which provide strong theoretical foundation to the nondestructive detector engineer.

Numerical Calculation of Optical Properties of Linear Nano-Graphite Particles

Using the discrete dipole approximation method, the absorption, scattering, extinction efficiency factor and differential scattering cross section of four kinds of nano-graphite particles under different incident angle are numerical calculated, the result shown that the value of the absorption, scattering, extinction efficiency factor and differential scattering cross section of linear nano-graphite particles are symmetric on the incident angle. There are the same variation tendency of absorption and extinction efficiency factor changed with the incident angle, when the incident light parallel with the linear nano-graphite particles, both the absorption and extinction are the strongest, and when the incident light perpendicular the linear nano-graphite particles, both the absorption and extinction are the weakest. The variation tendency of scattering efficiency factor changed with incident angle depended on the number of single graphite and the arrangement of linear nano-graphite particles. The value of differential scattering cross section is the smallest while the incident light parallel with the linear nano-graphite particles, however, the biggest while the incident light perpendicular the linear nano-graphite particles.

Scattering by a Conducting Infinite Cylinder Illuminated with a Gaussian Beam

An expansion of the incident Gaussian beam in terms of the cylindrical vector wave functions natural to an infinite cylinder of arbitrary orientation is presented. With such an expansion, the problem of interaction between a Gaussian beams and an infinite cylinder is studied in the framework of the generalized Lorenz-Mie theory. As an example, for the case of a tightly focused Gaussian beams propagating perpendicularly to the cylinder axis, the scattering characteristics are described in detail, and numerical results of the normalized differential scattering cross section are evaluated.

Extracting the pair distribution function from white-beam X-ray total scattering data

A general method is described for reducing white-beam X-ray total scattering raw data to the differential scattering cross section and pair distribution function. The method incorporates corrections for X-ray fluorescence,Bremsstrahlungradiation, polarization, attenuation, multiple scattering and sample container scattering, and invokes the Krogh-Moe and Norman method to put the data on an absolute scale. An accurate method to convert the differential scattering cross section to the pair distribution function is also described, and a rigorous and revised Lorch function is proposed for removing the effects of Fourier truncation oscillations. The method can be equally applied to synchrotron X-ray data, where the data analysis can be simpler than at a laboratory source.