Uday K. Khankhoje

Modelling and fabrication of GaAs photonic-crystal cavities for cavity quantum electrodynamics

In this paper, we present recent progress in the growth, modelling, fabrication and characterization of gallium arsenide (GaAs) two-dimensional (2D) photonic-crystal slab cavities with embedded indium arsenide (InAs) quantum dots (QDs) that are designed for cavity quantum electrodynamics (cQED) experiments. Photonic-crystal modelling and device fabrication are discussed, followed by a detailed discussion of different failure modes that lead to photon loss. It is found that, along with errors introduced during fabrication, other significant factors such as the presence of a bottom substrate and cavity axis orientation with respect to the crystal axis, can influence the cavity quality factor (Q). A useful diagnostic tool in the form of contour finite-difference time domain (FDTD) is employed to analyse device performance.

Inverse Scattering Using a Joint

Inverse scattering problems suffer from ill-posedness and ill-conditioning, necessitating the use of regularization methods to get meaningful solutions. Commonly used regularizations are L2 norm based, but these generate over-smooth solutions. We propose a regularization method using both the L1 and L2 norms to obtain sharp object boundaries, while also achieving good interior reconstruction of the object permittivity. Knowledge about the permittivity can also be used as a priori information. The applicability of the method is demonstrated on synthetically generated data for two-dimensional (2-D) microwave imaging using the Born-iterative method (BIM). The optimization routine systematically estimates all parameters, while minimizing the cost function. Different objects chosen to represent realistic features have been considered to evaluate the performance. The reconstructed images indicate that the method can produce accurate object localization, shape identification, and good permittivity estimation.

L1-L2

A 2-D vector-element-based finite-element method (FEM) is used to calculate the radar backscatter from 1-D bare rough soil surfaces which can have an underlying heterogeneous substrate. Monte Carlo simulation results are presented for scattering at L-band (λ = 0.24 m). For homogeneous soils with rough surfaces, the results of FEM are compared with the predictions of the small perturbation method. In the case of heterogeneous substrates, soil moisture (and, hence, soil permittivity) is assumed to vary as a function of depth. In this case, the results of FEM are compared with those of the transfer matrix method for flat soil surfaces. In both cases, a good agreement is found. For homogeneous rough soils, it is found that polarimetric radar backscatter and copolarized phase difference have a nonlinear relationship with soil moisture. Finally, it is found that the nature of the soil moisture variation in the top few centimeters of the soil has a strong influence on the backscatter and, hence, on the inferred soil moisture content.

Norm-Based Regularization

We investigate high-Q, small mode volume photonic crystal nanobeam cavities using a curved, tapered optical microfiber loop. The strength of the coupling between the cavity and the microfiber loop is shown to depend on the contact position on the nanobeam, angle between the nanobeam and the microfiber, and polarization of the light in the fiber. The results are compared to a resonant scattering measurement.

Computation of Radar Scattering From Heterogeneous Rough Soil Using the Finite-Element Method

A large obstacle for realizing quantum photonic logic is the weak optical nonlinearity of available materials, which results in large power consumption. In this paper, we present the theoretical design of all-optical logic with second order (

Characterization of 1D Photonic Crystal Nanobeam Cavities Using Curved Microfiber

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Cavity enhanced second-order nonlinear photonic logic circuits

) nonlinear bimodal cavities and their networks. Using semiclassical models derived from the Wigner quasi-probability distribution function, we analyze the power consumption and signal-to-noise ratio (SNR) of networks implementing an optical AND gate and an optical latch. Comparison between the second and third order

A Perturbative Solution to Plane Wave Scattering From a Rough Dielectric Cylinder

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On the Accuracy of Averaging Radar Backscattering Coefficients for Bare Soils Using the Finite-Element Method

optical logic reveals that while the

A mesh reconfiguration scheme for speeding up Monte Carlo simulations of electromagnetic scattering by random rough surfaces

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