Deterministic control of light scattering through disordered media for photonic applications

Abstract

Light propagation through a disordered system is a fundamental physical phenomenon that associated with a variety of practical applications as well as fundamental optical research. When a light propagates through a medium that is highly disordered, such as opaque paint layer, human skin, dense fog, or the medium consisting of complex refractive index distributions, the multiple light scattering occurs. The paths of propagating lights are completely scrambled and result in the loss of information of the propagating waves. Although the multiple light scattering seemingly a stochastic phenomenon due to its complexity, in the classical electrodynamics, the phenomenon is deterministic, which is derived by Maxwell’s equations. Based on the deterministic nature, the light scatterings are readily controlled by shaping the incident light and the disordered medium can be used as optical elements where its functionalities are beyond the conventional optics.

In this thesis, we demonstrate deterministic control of light scatterings through disordered systems for practical photonic applications. Rather than avoid the multiple light scatterings induced by the disordered systems, we intentionally utilize it for exploiting high degree of freedom brought on by the disordered systems. The thesis consists of two parts: manipulating light with (1) a conventional disordered medium that can be easily found in nature and (2) a disorder-engineered medium. In the first category, we introduce a scattering optical element which is a universal wavefront transformer that exploits multiple light scattering occurred in a layer of titanium dioxide nanoparticles. The high degree of freedom brought on by the disordered medium enables to address various optical properties of scattered light in the manner of wavefront shaping. In the latter category, we propose a disorder-engineered optical system, which does not require extensive characterization of optical responses of the disordered systems. Specifically, we introduce a non-periodic photon sieve where the lateral positions of the pinholes are designed in a pseudo-random manner. The capability of disordered-engineered photonic structure which relates low spatial frequency components to high spatial frequency components enables the realization of large-area wide-viewing angle 3D holographic display.