Design and Characterization of Multifunctional Thermal Meta-Optics

Abstract

Miniaturization of optical components, namely, lenses for high-quality cameras are ubiqituous in today’s world. The phone cameras which we carry around in our pocket consist of a series of lenses that are governed by the same principles of optics that were known centuries ago. The capability to shrink optical components for integration in larger, complex assemblies is of great importance for size, weight and power (SWaP)-constrained applications. The oldest category of optical lenses, refractive lenses, can be limiting in modern technology due to their volume. On the other hand, diffractive optics have found great success particularly with added control and tunability for light propagation. The micro- or nanostructure array that comprise a recently established type of diffractive optical element are known as meta-optics. In particular, for applications where reduced bulk is important, metasurfaces are a promising solution given their ultrathin form-factor and fabrication process flows which may be compatible with semiconductor foundry techniques. The individual meta-atoms that comprise a metasurface have sub-wavelength periodicity. Through designing the optical response of each meta-atom unit, a metasurface can be designed with a specific phase, amplitude, and polarization which is not constrained by the aperture size. For the infrared wavelength bands, SWaP considerations become more stringent as the optics scale with the wavelength.1 In this dissertation, we examine the effects of broadband imaging in a computational imaging system across the MWIR band and show the performance by a single-wavelength hyperboloid metalens. We also demonstrate the fabrication capabilities of centimeter-scale meta-optics with metasurfaces designed with unique approaches including synthetic apertures and Fresnel zone phases. The effect of photolithography fabrication for polarization-dependent meta-optics is also demonstrated towards the end of depth estimation imaging. These applications present the unique potential of metasurfaces to replace traditional lens counterparts in applications focused in the infrared bandwidths including imaging, sensing, and spectroscopy.