This thesis presents a novel micron-sized trapezoidal plasmonic waveguide design, called an Interface Plasmon Polariton waveguide. The guiding mechanism is explained using an effective index method and validated by simulations. The mode cut-off conditions and single-mode guiding properties are both determined using simulation and experimentally demonstrated. The waveguides have a long 1 mm propagation distance at 1550 nm wavelengths. Using this IPP waveguide, novel dielectric rib, dielectric varying-density hole-array, and metal-groove Bragg grating $\emph{in vitro}$ sensors are designed, fabricated, and characterized. The devices have a 1100 nm/RIU sensitivity and 0.006 RIU sensing resolution obtained from measurements and are validated by theory. The IPP sensors developed in this thesis not only offer competitive plasmonic sensitivity, sensing resolution, signal to noise ratio, result reproducibility, and reusability, they are also easy to fabricate and simple to package. Therefore, these new sensor designs are an enabler for lab-on-a-chip platforms to adapt plasmonic technology.

This thesis presents a novel micron-sized trapezoidal plasmonic waveguide design, called an Interface Plasmon Polariton waveguide. The guiding mechanism is explained using an effective index method and validated by simulations. The mode cut-off conditions and single-mode guiding properties are both determined using simulation and experimentally demonstrated. The waveguides have a long 1 mm propagation distance at 1550 nm wavelengths. Using this IPP waveguide, novel dielectric rib, dielectric varying-density hole-array, and metal-groove Bragg grating $\emph{in vitro}$ sensors are designed, fabricated, and characterized. The devices have a 1100 nm/RIU sensitivity and 0.006 RIU sensing resolution obtained from measurements and are validated by theory. The IPP sensors developed in this thesis not only offer competitive plasmonic sensitivity, sensing resolution, signal to noise ratio, result reproducibility, and reusability, they are also easy to fabricate and simple to package. Therefore, these new sensor designs are an enabler for lab-on-a-chip platforms to adapt plasmonic technology.

Active plasmonics combines the manipulation of light on both sub-wavelength length and ultrashort time scales, a unique meld that holds promise for developments in many scientific fields. This thesis reports on a novel approach to ultrafast, all-optical control of grating-assisted excitation of surface plasmon polaritons based on opto-thermally modifying the optical properties of gold. In contrast to prior works, this approach results in plasmonic modulation on picosecond and even sub-picosecond time scales, and is compatible with modern, multi-GHz information processing technology. Finally, an analytic model is developed that allows for the rapid and accurate calculation of the coupling efficiency of beams with arbitrary spatial profile. First, the ultrafast dynamics of existing plasmonic coupling resonances, on gold films with grating overlayers, are studied with spectrally resolved pump-probe measurements. Irradiation of the metal by 700 fs, 775 nm laser pulses results in modulations of the plasmonic coupling efficiency of ~20% near the center, or ~60% off-center, of resonances centered between 540 nm and 700 nm. The modulations decay with a time constant of 770 +/- 70 fs. The experimental results are consistent with simulations based on the thermal-dynamics of the electron-lattice gold system, coupled with numerical modeling of light-grating interactions. Next, two 150 fs, 810 nm laser beams are interfered on the surface of a planar gold film, leading to an absorption/refraction grating in the metal. Optical pump-probe spectroscopy measurements of the first (-1) diffracted order in transmission identify plasmonic coupling resonances between 520 nm and 570 nm. The observed coupling efficiency is ~10^{-5}, and the launch window decays with a time constant of 620 +/- 100 fs. Lastly, a Green function-based analytic model is developed to describe grating assisted plasmonic coupling, culminating in a first-order differential equation with coefficients that have both clear physical significance as well as analytic forms. Comparison of this technique with standard numerical modeling methods shows that plasmonic coupling efficiencies in excess of 0.8 are predicted within an error of 15%. This model is used to study plasmonic excitation by finite-size beams, showing the spatial evolution of the intensity of both the surface plasmon polariton and the reflected beam.

Active plasmonics combines the manipulation of light on both sub-wavelength length and ultrashort time scales, a unique meld that holds promise for developments in many scientific fields. This thesis reports on a novel approach to ultrafast, all-optical control of grating-assisted excitation of surface plasmon polaritons based on opto-thermally modifying the optical properties of gold. In contrast to prior works, this approach results in plasmonic modulation on picosecond and even sub-picosecond time scales, and is compatible with modern, multi-GHz information processing technology. Finally, an analytic model is developed that allows for the rapid and accurate calculation of the coupling efficiency of beams with arbitrary spatial profile. First, the ultrafast dynamics of existing plasmonic coupling resonances, on gold films with grating overlayers, are studied with spectrally resolved pump-probe measurements. Irradiation of the metal by 700 fs, 775 nm laser pulses results in modulations of the plasmonic coupling efficiency of ~20% near the center, or ~60% off-center, of resonances centered between 540 nm and 700 nm. The modulations decay with a time constant of 770 +/- 70 fs. The experimental results are consistent with simulations based on the thermal-dynamics of the electron-lattice gold system, coupled with numerical modeling of light-grating interactions. Next, two 150 fs, 810 nm laser beams are interfered on the surface of a planar gold film, leading to an absorption/refraction grating in the metal. Optical pump-probe spectroscopy measurements of the first (-1) diffracted order in transmission identify plasmonic coupling resonances between 520 nm and 570 nm. The observed coupling efficiency is ~10^{-5}, and the launch window decays with a time constant of 620 +/- 100 fs. Lastly, a Green function-based analytic model is developed to describe grating assisted plasmonic coupling, culminating in a first-order differential equation with coefficients that have both clear physical significance as well as analytic forms. Comparison of this technique with standard numerical modeling methods shows that plasmonic coupling efficiencies in excess of 0.8 are predicted within an error of 15%. This model is used to study plasmonic excitation by finite-size beams, showing the spatial evolution of the intensity of both the surface plasmon polariton and the reflected beam.

The motivation of this study lies in the necessity for a microfocal therapy to specifically target diseased areas in vascular pathologies such as age-related macular degeneration (AMD). AMD is the most common cause of legal blindness among people over the age of 60 in developed countries. This degenerative condition affects the macula, the central region of the retina, severely impairing detailed vision and hindering everyday activities. Worldwide, 25-30 million people live with some form of AMD. Among them, ~10% suffer from the more advanced and damaging form, wet-AMD, which causes rapid and severe loss of central vision. To date, there is no cure or long-term alternative for this degenerative disease despite intensive research efforts. With recent developments in biophysical tools and experimental procedures, in this study, we demonstrate a highly-localized therapeutic option: two-photon (2-photon) photodynamic therapy (PDT) that could be advantageous for the cure of wet-AMD, either alone or in combination with recently discovered anti-angiogenic therapies. This new approach offers selective targeting of the diseased area, thus minimizing damage to the surrounding sensitive healthy eye tissues, which is a major concern with the clinically-used, standard wide-beam, one-photon (1-photon) PDT. The objective of the research was to test the feasibility of microfocal 1-photon and the inherently localized 2-photon PDT, their optimization and also to evaluate the efficacy of existing 1-photon and novel 2-photon photosensitizers. In this thesis, I illustrated the in vitro (endothelial cell monolayer) and in vivo (window chamber mouse (WCM)) models that can be used to quantitatively compare the 2-photon efficiency of photosensitizers. Using the in vitro model, I compared the 2-photon efficacy of clinically used 1-photon PDT drugs Photofrin and Visudyne, and showed that the Visudyne is an order of magnitude better 2-photon photosensitizer than Photofrin. With the WCM model, I demonstrated a novel designer 2-photon photosensitizer is 20 times more efficient than Visudyne for single vessel occlusion. I also generated the drug and light dose reciprocity curve for localized single-vessel microfocal PDT. This is a necessary step towards applying the method to the relevant ocular models of AMD, which is the next phase for this research.

Doctor of Philosophy / Department of Physics / Brett DePaola / Zenghu Chang / Extremely broad bandwidth attosecond pulses (which can support 16as pulses) have been demonstrated in our lab based on spectral measurements, however, compensation of intrinsic chirp and their characterization has been a major bottleneck. In this work, we developed an attosecond streak camera using a multi-layer Mo/Si mirror (bandwidth can support ~100as pulses) and position sensitive time-of-flight detector, and the shortest measured pulse was 107.5as using DOG, which is close to the mirror bandwidth. We also developed a PCGPA based FROG-CRAB algorithm to characterize such short pulses, however, it uses the central momentum approximation and cannot be used for ultra-broad bandwidth pulses. To facilitate the characterization of such pulses, we developed PROOF using Fourier filtering and an evolutionary algorithm. We have demonstrated the characterization of pulses with a bandwidth corresponding to ~20as using synthetic data. We also for the first time demonstrated single attosecond pulses (SAP) generated using GDOG with a narrow gate width from a multi-cycle driving laser without CE-phase lock, which opens the possibility of scaling attosecond photon flux by extending the technique to peta-watt class lasers. Further, we generated intense attosecond pulse trains (APT) from laser ablated carbon plasmas and demonstrated ~9.5 times more intense pulses as compared to those from argon gas and for the first time demonstrated a broad continuum from a carbon plasma using DOG. Additionally, we demonstrated ~100 times enhancement in APT from gases by switching to 400 nm (blue) driving pulses instead of 800 nm (red) pulses. We measured the ellipticity dependence of high harmonics from blue pulses in argon, neon and helium, and developed a simple theoretical model to numerically calculate the ellipticity dependence with good agreement with experiments. Based on the ellipticity dependence, we proposed a new scheme of blue GDOG which we predict can be employed to extract intense SAP from an APT driven by blue laser pulses. We also demonstrated compression of long blue pulses into >240 µJ broad-bandwidth pulses using neon filled hollow core fiber, which is the highest reported pulse energy of short blue pulses. However, compression of phase using chirp mirrors is still a technical challenge.

This thesis presents designs and fabrication algorithms for 3D photonic band gap (PBG) material synthesis and embedded optical waveguide networks. These designs are suitable for large scale micro-fabrication using optical lithography methods. The first of these is a criss-crossing pore structure based on fabrication by direct photo-electrochemical etching in single-crystal silicon. We demonstrate that a modulation of the pore radius between pore crossing points leads to a moderately large PBG. We delineate a variety of PBG architectures amenable to fabrication by holographic lithography. In this technique, an optical interference pattern exposes a photo-sensitive material, leading to a template structure in the photoresist whose dielectric-air interface corresponds to an iso-intensity surface in the exposing interference pattern. We demonstrate PBG architectures obtainable from the interference patterns from four independent beams. The PBG materials may be fabricated by replicating the developed photoresist with established silicon replication methods. We identify optical beam configurations that optimize the intensity contrast in the photoresist. We describe the invention of a new approach to holographic lithography of PBG materials using the diffraction of light through a three-layer optical phase mask (OPM). We show how the diffraction-interference pattern resulting from single beam illumination of our OPM closely resembles a diamondlike architecture for suitable designs of the phase mask. It is suggested that OPML may both simplify and supercede all previous optical lithography approaches to PBG material synthesis. Finally, we demonstrate theoretically the creation of three-dimensional optical waveguide networks in holographically defined PBG materials. This requires the combination of direct laser writing (DLW) of lines of defects within the holographically-defined photoresist and the replication of the microchip template with a high refractive index semiconductor such as silicon. We demonstrate broad-band (100-200~nm), single-mode waveguiding in air, based on the light localization mechanism of the PBG as well as sharp waveguide bends in three-dimensions with minimal backscattering. This provides a basis for broadband 3D integrated optics in holographically defined optical microchips.

The structure and structural dynamics of hydrogen bonded liquids were studied experimentally and theoretically with coherent two-dimensional infrared (2DIR) spectroscopy. The resonant intermolecular interactions within the fully resonant hydrogen bond networks give access to spatial correlations in the dynamics of the liquid structures. New experimental and theoretical tools were developed that significantly reduced the technical challenges of these studies. A nanofluidic flow device was designed and manufactured providing sub-micron thin, actively stabilized liquid sample layers between similarly thin windows. A simulation protocol for nonlinear vibrational response calculations of disordered fluctuating vibrational excitons was developed that allowed for the first treatment of resonant intermolecular interactions in the 2DIR response of liquid water. The 2DIR spectrum of the O-H stretching vibration of pure liquid water was studied experimentally at different temperatures. At ambient conditions the loss of frequency correlations is extremely fast, and is attributed to very efficient modulations of the two-dimensional O-H stretching vibrational potential through librational motions in the hydrogen bond network. At temperatures near freezing, the librational motions are significantly reduced leading to a pronounced slowing down of spectral diffusion dynamics. Comparison with energy transfer time scales revealed the first direct proof of delocalization of the vibrational excitations. This work establishes a fundamentally new view of vibrations in liquid water by providing a spatial length scale of correlated hydrogen-bond motions. The linear and 2DIR response of the amide I mode in neat liquid formamide was found to be dominated by excitonic effects due to largely delocalized vibrational excitations. The spectral response and dynamics are very sensitive to the excitonic mode structure and infrared activity distributions, leading to a pronounced asymmetry of linear and 2DIR line shapes. This was attributed to structurally different species in the liquid characterized by their degree of medium range structural order. The response is dominated by energy transfer effects, sensitive to time-averaged medium range structural order, while being essentially insensitive to structural dynamics. This work is the first to recognize the importance of energy transfer contributions to the 2DIR response in a liquid, and provides additional proof of the well-structured character of liquid formamide.

A new laser ablation mechanism of liquid water based on recent insights into its hydrogen bond dynamics has been studied and several applications of the ablation demonstrated. The mechanism, termed as Impulsive Heat Deposition through Vibrational Excitations (IHDVE), is based on the ability of the hydrogen bond network of water to rapidly thermalize vibrational O-H stretch excitations on a time scale of several picoseconds even for excitation intensities that are large enough to bring excited volumes far into the supercritical region. In this way, by using vibrationally resonant picosecond infrared laser pulses with sufficient energy, it is possible to drive ultrafast phase transitions in the excited water volume leading to a rapid and efficient ablation process of water and water rich targets with minimum perturbation of solute molecules of interest. The physics behind the IHDVE ablation process is outlined and the benefits of the IHDVE ablation are demonstrated for two important applications of tissue cutting and mass spectrometry of biomolecules. Finally, the development of two high power infrared laser systems suitable for the practical implementation of IHDVE is presented.

This thesis aims at both developing highly nonlinear Aluminum Gallium Arsenide waveguides(AlGaAs) and demonstrating all-optical wavelength conversion via cross-phase modulation in AlGaAs waveguides at telecommunications wavelengths. This work covers waveguide design, device fabrication, device characterization and system work.