<p> Observing the non-equilibrium dynamics of the invisible ultrafast atomic and sub atomic world requires optical tools with ultrashort bursts of light and wavelengths. Such optical sources can provide us with the ultimate understanding of the quantum universe in the 4D space-time continuum at femto-zeptosecond time and nano-picometer spatial scale. Revealing at the same time, the 'extra dimensions' of the chemical nature of matter with elemental specificity, e.g., oxidation, charge/spin localization to specific elements, etc. To expand the frontiers of knowledge, there is a simple solution: coherent ultrafast X-ray or gamma&ndash;ray laser light. Amongst the numerous X-ray light sources that exist or have been developed to date, there are just two practical complementary alternatives: giant free electron X-ray laser facilities and compact high harmonic generation X-ray lasers. This thesis focuses on the latter. </p><p> High harmonics result from the extreme nonlinear response of matter to strong laser fields. However, due to inability to phase match, the available bright HHG sources were limited to the EUV spectral region ~0.15<i> keV.</i> We report on two routes for efficiently obtaini bright, coherent X-ray light. The first approach, takes advantage of the ultra-high emission per atom and ion species, the large refractive indices, and small phase mismatch, using high intensity UV lasers. Here the specifics of the phase matching and group velocity matching lead to bright soft X-ray emission from ions and atoms, even at ionization levels above 500%. Using UV light at 0.270<i>&micro;m, </i> the harmonics extend above 280<i>eV</i> while the expec phasematching cutoff was believed to be 23<i>eV</i>. Second, using IR lasers, where the process o phase matching favors the coherent buildup of X-rays from many atomic emitters at high gas density over long distances at extremely low ionization levels. The X-rays supercontinua driven by Mid-IR light at &lambda;_L = 3.9<i>&micro;m,</i> extends over ~12 octaves to > 1.6<i>keV,</i> and broadest spectrum generated to date from any small or large source. Calculations indicate that we can extend further the emission to the hard X-ray region and beyond using high laser intensity UV-EUV lasers or low intensities IR-Far IR lasers, without significantly sacrificing the X-ray flux. However, special highly transmissive fibers are required for phase matching in the Mid-IR region, where the propagation distances are longer than the self-guiding lengths. In addition, the flux from the Mid-IR driven HHG is expected to decrease substantially or cease due to a large <i>v</i> vector &times; <i>B</i> vector drift of the returning electrons caused by th magnetic field <i> B</i> vector and because of the large quantum diffusion of the electron wavepacket. We propose and design special photonic bandgap waveguides to resolve all the issues limiting the flux of IR and Mid-IR and UV driven hard X-rays. </p><p> The properties of the X-rays, driven by UV and IR lasers, are completely contrasting: supercontinuum versus isolated sharply peaked harmonics, we predict chirped isolated single pulses on sub or femtosecond scale as opposed to near transform limited train of attosecond pulses, respectively for IR and UV-driven harmonics. While pressure phase matching has been widely used we introduce the concept of pressure-temperature tuned phase matching for the process of HHG generation that additionally increases the flux. </p><p> Moreover, we report on harmonic generation with extremely high flux at near <i>mW</i> and <i>&micro;J</i> level, that allows us to perform experiments, which were previously only possible in large-scale facilities. While a magnetic scattering cross section is orders of magnitude smaller than the charge scattering cross section, we demonstrate resonant magnetic ptychography coherent diffraction imaging at the <i>Fe, M</i>-edge, using narrow bandwidth X-rays light, to lo at buried magnetic domain structure. Using broad 'water window' and keV coherent X-ray supercontinua, we extract atomic structure on picometer spatial resolution and chemical bonds' information, through x-ray absorption spectroscopy measurements at various absorption edges. </p><p> Such unique light tools will make it possible to answer even questions that have not yet been asked or may have never been imagined.</p><p>

A new high resolution Fourier transform interferometer has been constructed for the study of infrared molecular spectra. The instrument is capable of producing high quality spectra with an unapodized resolution of.004 cm$\sp{-1}$ for the wavenumber range 2000 to 10000 cm$\sp{-1}$. Described here are the details of construction and operating procedures for this instrument as well as the data collection, control and analysis software written specifically for it. / The new FTS instrument has been used to measure the torsion-rotation absorption spectrum of the O-H stretch vibration in gaseous hydrogen peroxide. Over 3000 line assignments have been made, including many arising from torsional "hot band" transitions. Many new assignments have been made for the weak n = 0$\to$1 bands and assignments for the very weak n = 1$\to$2 bands are reported for the first time. These new data have been used to determine the torsion-rotation energy levels and inertial constants for each of the five lowest torsion states of the excited antisymmetric O-H stretch. The shape of the potential curve was estimated from these using a semi-rigid rotor model; the limitations of the model are examined. / Source: Dissertation Abstracts International, Volume: 53-07, Section: B, page: 3554. / Major Professor: Robert H. Hunt. / Thesis (Ph.D.)--The Florida State University, 1992.

<p> This dissertation encompasses experimental and theoretical studies on two cornerstones of modern nonlinear optics: laser filamentation and harmonic generation. Laser filaments are self-guided light structures balanced by Kerr self-focusing and diffraction/plasma defocusing, enabling applications in lightning guiding, long-range spectroscopy, and high-precision laser weapons. Harmonic generation is a nonlinear process that up-converts optical frequencies, and it is a promising source of table-top, ultrashort X-ray/UV radiation. </p><p> The goal of this work is two-fold: control and visualization of nonlinear optical phenomena. First, variable focusing geometries are used to eliminate high-power laser multifilamentation, which is a stochastic process that is notoriously difficult to control. Next, two-color pump-probe experimental schemes are used to enhance third-harmonic generation in air by several orders of magnitude. Our experimental results agree well with calculations based on state-of-the-art unidirectional pulse propagation equations, which give insight into the physical mechanisms underlying our experimental findings. An overarching theme of this work is ultrafast visualization: by combining femtosecond-time-resolved pump-probe methods with advanced quantitative phase microscopy, we can visualize and quantitatively characterize dynamically-evolving micro-structures during various nonlinear laser-matter interactions. Finally, this work will describe some novel properties of mid-infrared and long-wavelength infrared ultrashort pulse propagation, with a focus on the generation of light bullets, which represent a holy grail of nonlinear optics.</p><p>

In emission spectral measurement with a dispersive spectrometer, if the entrance slit is widely opened, more light from a relatively large sample area can be collected, thus both energy throughput and spatial averaging advantages can be achieved in the measurement. With the entrance slit widely opened, the spectral bandpass becomes large. Radiations of different wavelengths likely fall on the same area of the detector. This can lead to a multiplex advantage and also extend the accessible wavelength range for a given spectral window. / The problem for opening the entrance slit is the decrease of spectral resolution. This project aimed to overcome this problem so that all the advantages associated with opening entrance slit are retained without loss of spectral resolution. The research we have done to solve this problem is to apply Hadamard transform and deconvolution in spectral measurements. The way we implement Hadamard transform in emission spectroscopy is to take spectra with a Hadamard mask in place of the conventional entrance slit, then inversely transform the measured data to recover the well-resolved spectra with improved signal-to-noise ratio. A spectrum can also be taken simply with the entrance slit widely opened. By deconvolving the slit function with such a wide-slit spectrum a best resolved spectrum can be recovered. Major difficulties involving in deconvolution have been discussed in Chapter 5 of this dissertation, and a novel algorithm is proposed there as well. Another important aspect involved in this project is the incorporation of fiber optics with Hadamard transform and deconvolution in spectral measurements. This greatly improved the flexibility and collection efficiency in our measurement system. / Source: Dissertation Abstracts International, Volume: 52-10, Section: B, page: 5236. / Major Professor: Charles K. Mann. / Thesis (Ph.D.)--The Florida State University, 1991.

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The local surface plasmon resonance (LSPR) of noble metal nanoparticles has recently been exploited in numerous applications. The LSPR peak position and linewidth have been studied quite extensively, but the magnitude of the resonance has not received much attention. Analytical solutions to Maxwell's Equations cannot predict the scattering cross section of arbitrarily-shaped particles at arbitrary illumination and detection angles. Dark field microscpectroscopy is a powerful tool for studying plasmon resonances of noble metal nanoparticles and for developing their applications in sensing and imaging. We present a technique for calibrating dark field microspectrometer measurements to yield quantitative spectral scattering cross sections for arbitrarily shaped particles. Values for gold nanorods and gold bipyramids are reported. The measurements suggest that, for small elongated particles, the signal can be predicted by approximations based on the total cross section.

A high conversion efficiency in acousto-optical (AO) modulation can be obtained through careful design of an acousto-optic modulator (AOM), as well as careful selection of the following: the AO crystal material, the orientation in the AO crystal with respect to direction of propagation of the acoustic wave, the piezoelectric transducer material, the orientation of the transducer material, and the AOM fabrication method. A class of AOM's has been introduced wherein the diffraction efficiency of the AOM is improved by augmenting the design of the AOM so as to produce two or more passes of the optical beams through the acoustic beam wherein the Bragg diffraction conditions are satisfied. The effects of changes in acoustic beam direction and optical beam directions of propagation for the multiple-pass configuration are described in this dissertation. An AOM is fabricated in order to test the predicted properties of the class of AOM's incorporating the multiple-pass of optical beams for improving the conversion efficiency in AO modulation. Certain ones of the predicted properties of the multiple pass class of AOM's are confirmed by double pass experimental results for the fabricated AOM.

Semiconductor lasers in the presence of weak external optical injection or feedback become unstable, exhibiting optical chaos. I use a multi longitudinal mode partial differential equation model to study many physically observable phenomenon. These include longitudinal mode hops induced by weak external injection and anti-phase dynamics among the longitudinal modes in the presence of weak feedback. Chaotic semiconductor lasers are shown to be good candidates for optical communication: synchronization is robust and messages may be multiplexed through the many longitudinal modes.

The topic of this dissertation is on the design and construction of miniature microscope objective optics. The design of miniature microscope objective is both similar and different from conventional microscope objective. The design and construction of two miniature microscope objectives are presented in this dissertation. The first one is a high numerical aperture (NA), water-immersion objective and it is a part of a fiber confocal reflectance microscope (FCRM). The second one is a moderate NA dry objective and it is a part of a miniature microscope array (MMA). The capability, complexity and fabrication method of the two miniature objectives are different but they both share some similar design traits as result of their miniaturization. FCRM's miniature objective has a NA of 1.0 and it is designed to operate at near infrared lambda = 1,064 nm. It is 7 mm in outer diameter and 21 mm in length (measured from object plane to image plane). This kind of dimension is approximately 10 times smaller than a conventional microscope objective of similar caliber. Sub-micrometer resolution has been experimentally demonstrated with this miniature objective. MMA's miniature objective has a NA of 0.4 and it is designed to operate over the visible spectrum. It is 1.2 mm in diameter and 9.4 mm in length. The image quality of MMA's miniature objective is experimentally demonstrated to be comparable to the state-of-art commercial microscope objective.