Publication Date

2019-04-24

Availability

Open access

Embargo Period

2019-04-24

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Physics (Arts and Sciences)

Date of Defense

2019-04-03

First Committee Member

Olga Korotkova

Second Committee Member

Kenneth J Voss

Third Committee Member

Seyed Mohammad Hashemi

Fourth Committee Member

Jessica Ramella-Roman

Abstract

Light modulation is a vital component in optical communications, imaging and sensing systems. It imparts information on the optical wave carriers and establishes the reliability of the communication links. In imaging systems, a modulated light source has the potential in exceeding the diffraction limit and achieving better contrast in images. Improving the performance of light modulating devices such as Spatial Light Modulators (SLMs), multiplexers, couplers and polarization controllers can substantially benefit optical sensing and signal processing. Phase modulation of light, as an important format of light modulation, has gained appreciably more attention than its amplitude modulation due to its remarkable sensitivity and close relation to spectrum, coherence and polarization of light. This dissertation focuses on active (artificial) and passive (natural) phase modulation of light including light source generation, light propagation in biological tissues and light scattering from deterministic or random media. For genuine light source generation, two aspects of phase modulation are discussed. One deals with modeling the complex degree of coherence for 1D and 2D sources. A straightforward sliding function method is first presented and simple conditions on the sliding function are derived. The other contribution consists of the experimental method of stationary beam synthesis from its coherent modes. As an example, the Im-Bessel correlated beam with a separable vortex phase is experimentally generated. Moving on to light propagation in biological tissues, the spectral density and the coherence state evolution in isotropic and anisotropic samples are explored and the light scintillation is examined. Finally, light scattering from hollow and semi-hollow 3d scatterers with ellipsoidal, cylindrical and Cartesian symmetries is presented. Interesting intensity patterns coming off these scatterers can lead to prospective applications in inverse problems. The Probability Density Functions (PDFs) of the instantaneous Stokes parameters on weak scattering are also calculated for random stationary scatterers with Gaussian statistics and Gaussian spatial correlation function. The illustrated sensitivity of the Stokes parameters' PDFs to incident light polarization and the scatterers' statistics is of importance for developing novel sensing, communication and imaging schemes operating in the presence of particulate collections.

Keywords

Phase modulation; Random; Light fields; Biophotonics; Coherence

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