Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 1231. Adviser: John A. Rogers. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--Lehigh University, 2007. / Adviser: Himanshu Jain.

Thesis (Ph.D.)--Lehigh University, 2007. / Adviser: Himanshu Jain.

Thesis (P.D.)--Lehigh University, 2008. / Adviser: Nelson Tansu.

Thèse (M.Sc.A.)--Université de Sherbrooke (Canada), 2007. / Titre de l'écran-titre (visionné le 1 février 2007). In ProQuest dissertations and theses. Publié aussi en version papier.

Thesis (Ph.D.)--Lehigh University, 2010. / Advisers: Marvin H. White; Ivan Biaggio.

Les travaux réalisés dans le cadre de cette thèse visent à étudier une géométrie de lasers XUV inspirée des lasers de puissance. Cette architecture, consistant en un injecteur (une source d'harmoniques d'ordre élevé) couplé à un amplificateur (plasma créé par laser), correspond à celle d'une chaîne laser de puissance dans la gamme spectrale de l'XUV. Le laser à 32,8 nm étudié ici, est produit par l'injection d'harmonique d'ordre élevé dans un plasma de krypton créé par Optical Field Ionisation (OFI). Ce schéma, initialement testé par T. Ditmire en 1995, a été validé en 2003 au Laboratoire d'Optique Appliquée avec un amplificateur plasma créé par l'interaction d'un laser intense et d'un milieu gazeux. Cette thèse s'inscrit dans la continuité de ce dernier travail en tentant d'aborder différents aspects liés, non seulement à une meilleure compréhension des processus physiques impliqués, mais aussi à la caractérisation spatio-temporelle de ce type de source.Nous avons démontré expérimentalement et pour la première fois qu'une source dans le domaine de l'XUV peut être à la fois très compacte, énergétique (1 µJ par impulsion), proche de la limite de diffraction et de celle de Fourier. En effet, grâce au filtrage spatial des harmoniques par le milieu amplificateur, le laser XUV injecté à 32,8 nm montre un profil spatial gaussien avec une divergence de 0,7 mrad (à 1/e2). Le front d'onde a été mesuré avec un senseur de type Hartmann et atteint une valeur de lambda/17 en écart quadratique moyen, démontrant que cette source XUV est limitée par la diffraction. Les caractérisations temporelles du laser montrent que le temps de cohérence est de l'ordre de la durée d'émission spontanée de l'amplificateur. Les résultats de la mesure de la cohérence temporelle présentent un profil gaussien de largeur spectrale relative delta lambda/lambda égale à 10-5 (à mi-hauteur) correspondant à une durée d'impulsion de l'ordre de 5 ps.

This thesis investigates the coherent phase modulation of ultrashort pulses using vibrating hydrogen as a molecular medium. Self-phase modulation in a gas-filled hollow core capillary allows the generation of highpower few-cycle pulses in the NIR. Such pulses can be used to drive high harmonic generation (HHG) to deliver attosecond duration pulses in the extreme ultraviolet and soft X-ray spectral region. While reaching unrivalled pulse durations (down to 67 as), these sources have characteristically low efficiencies. The pump-probe spectroscopy community would greatly benefit from brighter short wavelength sources with sub-5 fs duration. In this work I apply Amplified RamaN Impulsive Excitation for Molecular Phase Modulation (ARNIEMPM), a multiple pulse scheme, to coherently prepare vibrating hydrogen molecules and exploit them for the phase modulation of ultrashort pulses. The preparation of the molecular motion is performed via impulsive stimulated Raman scattering and transient stimulated Raman scattering. The generated in-phase motion of molecules creates an oscillating optical polarizability in the medium which can be exploited by a probe pulse propagating through it, acting as a 125THz frequency phase modulator, the fastest among molecular media. This technique has the potential to provide bright, isolated subfemtosecond duration ultra-violet (UV) pulses via spectral broadening of broadband pulses. I experimentally investigate the preparation of the molecular motion against multiple experimental parameters. I then demonstrate the molecular phase modulation of ultrashort broadband probes in the near-infrared (NIR) and UV via a degenerate interferometric scheme. I used a waveguide to increase the interaction length of the process and reduce the energy requirements for the medium preparation. This allowed the use of a single laser system to generate all the required pulses, which are largely diverse in terms of wavelength, duration and power. Additionally, I present a novel technique named Attosecond Resolved Interferometric Electric-field Sampling (ARIES), which is capable of directly measuring the waveform of arbitrary pulses with attosecond resolution. This technique is based on high-harmonic generation (HHG) acting as a temporal gate for an applied secondary field, and tracking its electric field amplitude as a shift in the HHG cut-off frequency. I present experimental demonstration of a pulse waveform measurement by accurately retrieving a know inserted variation in dispersion and carrier-envelope-phase. A theoretical calculation of the technique applicability over a wide spectral range is also presented.

Semiconducting nanocrystals in open-access microcavities are promising systems in which enhanced light-matter interactions lead to quantum effects such as the modulation of the spontaneous emission process and exciton-polariton formation. In this thesis I present improvements of the open cavity platform which serves to confine the electromagnetic field with mode volumes down to the λ³ regime and demonstrate results in both the weak and strong coupling regimes of cavity quantum electrodynamics with a range of different low-dimensional materials. I report cavity fabrication details allowing a peak finesse of 5 × 10⁴ and advanced photonic structures such as coupled cavities in the open cavity geometry. By incorporating two-dimensional materials and nanoplatelets in the cavity I demonstrate the strong coupling regime of light-matter interaction with the formation of exciton-polaritons, quasi-particles composed of both photon and exciton, at room temperature. In the perturbative weak coupling regime I show pronounced modulation of the single-photon emission from CdSe/ZnS quantum dots and the two-dimensional material WSe₂ and demonstrate Purcell enhancement of the spontaneous emission rate by factors of 2 at room temperature and 8 at low temperature. The findings presented in this thesis pave the way to establish open microcavities as a platform for a wide range of applications in nanophotonics and quantum information technologies.

Nanophotonic structures provide unique ways to control light and alter its behaviors in ways not possible in macroscopic structures. In this thesis, we explore novel behaviors of light created by nanophotonic structures, with a common theme on resonance effects. The first half of the thesis focuses on a peculiar type of electromagnetic resonance, where the resonance lifetime diverges to infinity. These states, called bound states in the continuum, remain localized in space even though their frequency lie within a continuum of extended modes. We find such states in photonic crystal slabs and the surface of bulk photonic crystals. We show the conditions necessary for them to exist, and provide the first experimental observation of these unusual states. We also show that these states have a topological nature, with conserved and quantized topological charges that govern their generation, evolution, and annihilation. The second half of the thesis concerns light scattering from resonant nanophotonic structures, where resonances can enhance or suppress scattering at particular wavelengths and angles. We show that multiple resonances in one nanostructure and in the same multipole channel generally lead to a scattering dark state where the structure becomes transparent. Based on the coherent interference from multiple scatterers, we show there are geometries that can achieve a sharp structural color where the hue, saturation, and brightness are all viewing-angle independent. We also invent a new type of transparent display based on wavelength-selective light scattering from nanostructures.