In this paper, we propose a fine scale partially coherent patch model (FPCP) for GNSS-R land applications for soil moisture retrieval. The land surface is divided into coherent planar patches on which microwave roughness is superimposed. The scattered waves of the coherent patch are decomposed into the coherent specular reflection and diffuse incoherent scattering. A fine scale of 2 meter patch size is chosen for the coherent patch to be applicable to complex terrain with large varieties of topographical elevations and with small to large topographical slopes. The summation of scattered fields over patches is carried out using physical optics. The phase term of the scattered wave of each patch is kept so that correlation scattering effects among patches are accounted for. Results are illustrated for power ratio for areas near the specular point and areas far away from the specular point. Comparisons are made with the radiative transfer geometric optics model. DDM simulations are performed with good agreement with CYGNSS data.
In this paper, high efficiency multi-functional all-optical logic gates based on a metal-insulator-metal (MIM) plasmonic waveguide structure with Kerr-type nonlinear nano-ring resonators are proposed. The proposed structure consists of three straight input ports, eight nano-ring resonators filled with the Kerr-type nonlinear medium, and one straight output port. By fixing the input signal power and properly changing the control power, it can be used to design high efficiency multi-functional all-optical logic gates. The numerical results show that the proposed Kerr-type nonlinear plasmonic waveguide structures could really function as all-optical XOR/NXOR, AND/NAND, and OR/NOR logic gates in the optical communication spectral region. The transmission efficiency of the high logic state is higher than 95%, and that of the low logic state is about 0% at the wavelength 1310nm. The performance of the proposed logic gates was analyzed and simulated by the finite element method (FEM).
In the simulation of high frequency nanoscale semiconductor devices in which electromagnetic (EM) fields and carrier transport are coupled, and optoelectronic devices in which strong interactions between EM fields and charged particles exist, both the Maxwell's equations and the time-dependent Schrödinger equation (TDSE) need to be solved to capture the interactions between EM and quantum mechanics (QM). One of the numerical simulation methods for solving these equations is the finite difference time domain (FDTD) method. In this review paper, the development of FDTD method applied in EM and QM simulation is discussed. Several widely used FDTD techniques, i.e., explicit, implicit, explicit staggered-time, and Chebyshev methods, for solving the TDSE are introduced and compared. The hybrid approaches based on FDTD method, which are used to solve the Poisson-TDSE and Maxwell-TDSE coupled equations for EM-QM simulation, are also discussed. Furthermore, the applications of these simulation methods for nanoscale semiconductor devices and optoelectronic devices are introduced. Finally, a conclusion is given.
χ(3) nonlinearity enables ultrafast femtosecond scale light-to-light coupling and manipulation of intensity, phase, and frequency. χ(3) nonlinear functionality in micro- and nano-scale photonic waveguides can potentially replace bulky fiber platforms for many applications. In this review, we summarize and comment on the progress on χ(3) nonlinearity in chip-scale photonic platforms, including several focused hot topics such as broadband and coherent sources in the new bands, nonlinear pulse shaping, and all-optical signal processing. An outlook of challenges and prospects on this hot research field is given at the end.
Quantum interactions between a single particle and nanoinclusions of spherical or cylindrical shape are optimized to produce scattering lineshapes of high selectivity with respect to impinging energies, excitation directions and cavity sizes. The optimization uses a rigorous solution derived via electromagnetic scattering formalism while the adopted scheme rejects boundary extrema corresponding to resonances that occur outside of the permissible parametric domains. The reported effects may inspire experimental efforts towards designing quantum sensing systems employed in applications spanning from quantum switching and filtering to single-photon detection and quantum memory.
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