Space-time wave packets (STWP) constitute a broad class of pulsed optical fields that are rigidly transported in linear media without diffraction or dispersion, and are therefore propagation-invariant in absence of optical nonlinearities or waveguiding structures. Such wave packets exhibit unique characteristics, such as controllable group velocities in free space and exotic refractive phenomena. At the root of these behaviors is a fundamental feature underpinning STWP: their spectra are not separable with respect to the spatial and temporal degrees of freedom. Indeed, the spatio-temporal structure is endowed with angular dispersion, in which each spatial frequency is associated with a single prescribed wavelength. Although the basic concept of STWPs has been known since the 1980s, only very recently has rapid experimental development emerged. These advances are made possible by innovations in spatio-temporal Fourier synthesis, thereby opening a new frontier for structured light at the intersection of beam optics and ultrafast optics. In this dissertation, I investigate the physics underlying STWPs and their applications in various fields of optics. Namely, I study crucial parameters that determine physical characteristics of STWPs, such as group velocity, access to low spatial frequencies, and classify STWPs into 10 distinct classes. In addition, I study the finite-energy STWP in the presence of finite apertures and find that the propagation-invariant distance is determined by the 'fuzziness' in space-time correlation underlying the field. Moreover, in the context of 2D STWPs (light sheets), I present an application where an in-line optical delay line is constructed based on tunability of group velocities of STWPs over a wide range of values from subluminal to superluminal velocities, demonstrating a delay-bandwidth product of ~100 for pulses of width of ~1 ps. Finally, by introducing a strategy capable of sculpting an arbitrary spatio-temporal spectral profile I extend the experimental technique to synthesize 3D STWPs localized in all dimensions with tunable group velocity in the range from 0.7c to 1.8c in free space, and endowed with prescribed orbital angular momentum. By providing unprecedented flexibility in sculpting the three-dimensional structure of pulsed optical fields, the new experimental strategy presented in the last part of the dissertation promises to be a versatile platform for the emerging enterprise of space-time optics.


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Graduation Date





Abouraddy, Ayman


Doctor of Philosophy (Ph.D.)


College of Optics and Photonics


Optics and Photonics

Degree Program

Optics and Photonics




CFE0009465; DP0027188





Release Date

November 2023

Length of Campus-only Access

1 year

Access Status

Doctoral Dissertation (Open Access)