A New Technique Combining Boundary Integral Equation and Hybrid Ray-Mode Method for Wave Scatters in Layered Background with Applications in Optical Microscopy

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This work is funded as an Engineering Initiation Award (EIA). Optical wave scattering phenomena for scatters embedded in a multilayer background will be studied using a new technique which employs boundary integral equation to formulate the interaction processes and hybrid ray- mode method to provide the Green's function of the background. This method is numerically efficient in a broad range of parameter regimes and also provides cogent physical interpretations for the computed result. Structures of interest in the optical microscopy of integrated circuits and integrated optics will serve as test cases. The dependance of the scattering properties on the shapes, sizes and dielectric constants of the scatters and the response of the scanning microscope to the scattering fields are to be investigated. The results gained from this research may enable the scanning microscopy to assess quantitatively objects whose dimensions are on the order of, or less than, the wavelength. Potential application is to the use of a scanning optical microscope for automated nondestructive evaluation and inspection of sub-micron structures in integrated circuits and integrated optics devices. This study will be also beneficial to other engineering disciplines such as nondestructive testing, exploration, geophysics and underwater acoustics, etc., where similar structures are investigated using elastic and acoustic waves. A new theoretical technique will be employed to study wave scattering phenomena of those structures that are of interest in scanned optical microscopy of integrated circuits and integrated optics. Such structures are composed of material formed in layers which often have embedded inhomogeneities, different from the background layered structure. One of the most versatile methods to identify and evaluate them is based on the use of the transmission and scattering bounded beams incident on the multilayered structure that are scanned over the region containing the scatter. In order to use the scattered fields to identify the properties of the scatter, it is essential to solve the direct problem of wave scattering by an object in a multilayer structure. This proposal addresses a use of the combination of boundary integral equation and the newly developed hybrid ray-mode method to solve the wave scattering problem.