Modeling and interactive design of multilayered spherical infrared optical filters using Mie theory

Abstract

The ability to manipulate the electromagnetic spectrum has long been an important factor in the field of photonics, however traditional optical filters are largely restricted to simple geometries due to practical limitations in fabrication. Recent developments in manufacturing technology has given engineers the ability to relax these restraints. A newly developed custom RF magnetron sputter deposition system located here at the University of Delaware has enabled the uniform coating of spherical micro particles. With this new fabrication technique, micro particles can be engineered to exhibit numerous application-based extinction profiles to produce highly effective optical filter aerosols, and so the need to simulate these new devices has become imperative. ☐ A custom Mie code was developed to assist in the design and modeling of non-homogeneous spheres with highly absorbing shells. By using the principles of classical Mie theory together with the implementation of a recursive algorithm scheme when calculating the Mie series coefficients, it is now possible to simulate the extinction and scattering efficiency curves for these highly absorbing multilayered spherical optical filters in the visible and infrared spectrum. The generated efficiency curves can then be passed through an optimization scheme depending on the user’s intent for particle design. ☐ The first part of this thesis will be focused on introducing the core concepts of optical filters and aerosol modeling. Next, the Mie theory and recursive algorithm methods employed in the custom optimization software will be explored. The custom Mie code, optimization schemes, and user interface will be outlined. This thesis will focus on two major designs, a particle with a high mass extinction coefficient in the mid-wave infrared, (MWIR, λ = 8-12µm) and a particle exhibiting a narrow pass-band filtering effect inside the short-wave infrared spectrum (SWIR, λ = 1-3µm). The remainder of this thesis will present numerical validations of my findings.