Date of Award

Spring 1-1-2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Margaret M. Murnane

Second Advisor

Henry C. Kapteyn

Third Advisor

Carlos Hernandez-Garcia

Fourth Advisor

Niels Damrauer

Fifth Advisor

Jun Ye

Abstract

Structured light, which is composed of custom-tailored light waves possessing nontrivial intensity, polarization, and phase, has emerged in recent decades as a powerful tool for probing and controlling light-matter interactions, with wide-reaching applications in fields ranging from microscopy, to scientific/industrial imaging, lithography, and even to forensic science. In particular, structured light possessing optical angular momentum can exhibit both spin and orbital flavors related to the polarization and topological phase structure of light, respectively. This new ability to sculpt light into complex optical patterns has proven to be particularly beneficial for telecommunications, quantum computing, chiral sensing, and super-resolution imaging, to name a few. By connecting principles of generating and controlling structured light with the extreme nonlinear process of high-harmonic generation, this thesis details how exquisite control can be attained over extreme ultraviolet attosecond light waves\textemdash in some cases rivaling and even surpassing the intricate structures so readily obtained at visible wavelengths.

Using novel optical control schemes, I first show that the ellipticity of attosecond pulse trains produced via high-harmonic generation can be actively controlled in real time, yielding attosecond pulses with a custom-tunable polarization state. These concepts are then taken a step further by adding controllable amounts of orbital angular momentum to the visible driving lasers, which yields full control over the polarization, divergence, and topological charge of short-wavelength, coherent light pulses. The use of spin-orbit driving beams provides unprecedented control over the emitted high-harmonics, allowing for the generation of, for example, spatially isolated short-wavelength vortex beams\textemdash and attosecond pulses\textemdash of pure circular polarization. Then in a final, beautiful result, I show experimentally that by driving the high harmonic upconversion process with a time-delayed pair of optical vortex beams, it is possible to create an entirely new property of propagating waveforms, that possess a self-torque. This novel property of light is manifested in extreme ultraviolet beams that exhibit a rapid, attosecond variation of their orbital angular momentum, which spans an entire octave of topological charges. In the future, these sculpted attosecond waveforms with designer spin and orbital angular momentum can serve as the basis for applying structured light waves to solving grand challenge problems in chemistry and physics, while also making it possible to tailor light-matter interactions on nanometer spatial and attosecond temporal scales.

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