Ubiquitous in nature, light-matter interactions constitute the pervasive foundation for many physical phenomena with application in optical and atomic physics, electrical and communication engineering, medicine, and biology. In many situations of interest, only the aftermath of light-matter interaction is experimentally accessible. The properties of light and matter are both encoded in the characteristics of this secondary source of radiation. In most cases, these field and intensity characteristics carrying information about the initial source of radiation or the specific material system are statistical in nature. A typical light-matter interaction experiment involves an initial source of radiation that interacts with a material system from which a secondary emission occurs. Measurements are usually performed on this secondary radiation, whose properties depend on both the characteristics of the primary source and the specifics of light-matter interaction. When the scope is to determine certain material properties, different approaches can be taken. For instance, one can actively modify the properties of the primary source of radiation to control different aspects of the interaction. This active modality offers great versatility in sensing applications. In many practical situations, however, accessing directly the primary source is simply not possible. In such circumstances, one is limited to so-called passive approaches where the sole source of information lies in the measurable properties of the secondary radiation. Contingent upon the intrinsic structural properties, the material system can be static or dynamic during the process of light-matter interaction and the experimental approaches may vary accordingly. In this thesis, we explore three different passive sensing scenarios based on different types of light-matter interactions. First, we examine a situation where the secondary radiation is the result of the continuous interaction between optical radiation and material systems with random structures that do not vary in time. In this case, we will discuss how the spatial coherence of the secondary emission can be used to extract information about either the static matter or the initial light source. Next, we study the cases when the secondary radiation originates from dynamic material systems in both steady-state and transient conditions. In the first case, when the matter is continuously excited, the intensity fluctuations are used to quantify the structural dynamics of the medium and retrieve its complex mechanical properties. As a particular application, we address the viscoelastic properties of blood, a typical example of a dynamic, optically-dense random medium. In the case of transient interactions, a low-intensity decaying signal is measured after the primary source shuts off. We discuss how subtle structural properties of matter can influence, even in these conditions, the rate of secondary emission.
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Doctor of Philosophy (Ph.D.)
College of Optics and Photonics
Optics and Photonics
Optics and Photonics
Length of Campus-only Access
Doctoral Dissertation (Campus-only Access)
Batarseh, Mahed, "On the Passive Sensing of Static and Dynamic Properties of Secondary Sources of Radiation" (2022). Electronic Theses and Dissertations, 2020-. 1461.
Restricted to the UCF community until November 2025; it will then be open access.