<p> Laser absorption spectroscopy is a non-intrusive diagnostic tool particularly well-suited to investigate the dynamic and harsh conditions commonly found within combustion systems. By measuring the amount of light absorbed at specific wavelengths that are resonant with rotational-vibrational transitions in molecules, absorption spectroscopy gives a measure of the molecular population in particular quantum states. Experimental spectra are fit with a simulation generated from spectral line shape models combined with a spectroscopic database to infer species concentrations, temperature, and pressure. Dual frequency comb spectroscopy (DCS) with mode-locked frequency comb lasers is an emerging form of absorption spectroscopy that yields both high resolution (&lt; 1 GHz) and broad bandwidth spectra (> 10 THz) on rapid timescales (&lt; 2 ms). There are two key challenges facing DCS in dynamic combustion environments. First, obtaining high signal-to-noise-ratio (SNR) spectra has traditionally involved coherently averaging hundreds of individual spectra over seconds to minutes before fitting. Second, at the high temperatures and pressures commonly found within combustion systems, the existing line shape models and spectroscopic databases are known to not capture all of the key molecular physics, thereby requiring empirical extension and validation. This work presents techniques to enable rapid DCS measurements of thermodynamic properties in dynamic high-pressure, high-temperature, environments through power optimization and apodization to improve the short-term SNR. A rapid compression machine at Colorado State University is instrumented with a portable DCS spectrometer and temperature is recovered at 704 &micro;s resolution from 1&ndash;21 bar and 294&ndash;566 K. This demonstrates the ability of DCS to be applied to combustion-relevant timescales for both broad bandwidth and high resolution non-intrusive measurements of harsh systems. The design development of an optical testbed that creates a well-known, high-temperature, and high-pressure environment is additionally discussed. This subsequently will enable determination of the accuracy limitations of existing molecular absorption models, as well as allow for model expansion. Together these abilities enable laser measurements to better evaluate and optimize combustion systems, including improved understanding of the underlying molecular processes. Proper understanding of the molecular dynamics will allow for instrumentation and quantification of more extreme environments such as inside rocket engines or the atmospheres of distant planets. </p><p>

<p> It is shown that the resolution of virtual images of dye-doped dielectric nanospheres obtained through dielectric microspheres can be increased beyond the classical diffraction limit by decreasing the period of nanoplasmonic array used for localized plasmonic structured illumination of these objects. In addition, it is also shown that post-imaging processing, which represents an intrinsic part of structured illumination microscopy, is not required for achieving the super-resolved images. This observation is interpreted due to the fact that the radiation of objects placed at the surface of nanoplasmonic arrays with sufficiently short periods can be almost completely redirected into folded dispersions of nanoplasmonic array, so that the diffraction orders responsible for super-resolution are more efficiently coupled to dielectric microspherical antenna compared to that for the uncoupled radiative modes. </p><p> Focal plane arrays (FPAs) are pixelated arrays of photo detectors which are widely used for imaging. The problem of uncooled mid-wave infrared (MWIR) FPAs is related to their large thermal noise. In this work, it is demonstrated that the surface area and thermal noise of pixels can be reduced without sacrificing their sensitivity by using integration with dielectric microspheres, which can be achieved by a novel method of suction assembly of microspheres in microhole arrays. In addition, it is demonstrated that alternative solution of this problem is offered by integration with microconical light concentrators, which can be fabricated by various well-established technologies including the use of the Nanoscribe. Using a simplified two-dimensional (2D) model, it is studied how the photocurrent depends on the geometrical parameters of microcones and on the angle of incidence. </p><p> The photoinduced aggregation of nanoparticles is of interest for material science and nonlinear optics applications. Light-driven assembly of nanoplasmonic particles is observed as an optical memory effect taking place due to the aggregation of 20 nm gold nanoparticles in the illuminated regions of the substrate after full evaporation of the liquid suspension. It is shown that the level of photoexcitation intensity required for observation of this effect is several orders of magnitude smaller compared to that in the previous studies of photoinduced aggregation typically performed using intense laser illumination. It is also demonstrated in a preliminary way that the photoinduced aggregation is facilitated in the spectral range resonant with localized surface plasmon resonances in nanoparticles. </p><p> Inverse scattering algorithms are of interest for many applications; however, they are usually based on low refractive index contrast approximations and measuring the phase distributions. In contrast, Globally Convergent Inverse Scattering (GCIS) algorithms in principle should allow phaseless image reconstruction for high refractive index objects. In order to test the operation of GCIS algorithms, high-index (n~2) barium titanate glass microspheres were assembled directly at a silicon chip of a cell phone camera and the scattering patterns resembling the shape of the Airy disks were detected using a set of narrow spectral filters throughout a broad range of wavelengths in the visible regime. The results were found to be in a good agreement with the image calculations and can be used for the object reconstruction based on GCIS algorithms.</p><p>

<p> Vertical-cavity surface-emitting lasers (VCSELs) have a long history of development in GaAs-based and InP-based systems, however III-nitride VCSELs research is still in its infancy. Yet, over the past several years we have made dramatic improvements in the lasing characteristics of these highly complex devices. Specifically, we have reduced the threshold current density from &sim;100 kA/cm² to &sim;3 kA/cm², while simultaneously increasing the output power from &sim;10 &mu;W to &sim;550 &mu;W. These developments have primarily come about by focusing on the aperture design and intracavity contact design for flip-chip dual dielectric DBR III-nitride VCSELs. We have carried out a number of studies developing an Al ion implanted aperture (IIA) and photoelectrochemically etched aperture (PECA), while simultaneously improving the quality of tin-doped indium oxide (ITO) intracavity contacts, and demonstrating the first III-nitride VCSEL with an n-GaN tunnel junction intracavity contact. Beyond these most notable research fronts, we have analyzed numerous other parameters, including epitaxial growth, flip-chip bonding, substrate removal, and more, bringing further improvement to III-nitride VCSEL performance and yield. This thesis aims to give a comprehensive discussion of the relevant underlying concepts for nonpolar VCSELs, while detailing our specific experimental advances. In Section 1, we give an overview of the applications of VCSELs generally, before describing some of the potential applications for III-nitride VCSELs. This is followed by a summary of the different material systems used to fabricate VCSELs, before going into detail on the basic design principles for developing III-nitride VCSELs. In Section 2, we outline the basic process and geometry for fabricating flip-chip nonpolar VCSELs with different aperture and intracavity contact designs. Finally, in Section 3 and 4, we delve into the experimental results achieved in the last several years, beginning with a discussion on the epitaxial growth developments. In Section 4, we discuss the most noteworthy accomplishments related to the nonpolar VCSELs structural design, such as different aperture and intracavity contact developments. Overall, this thesis is focused on the nonpolar VCSEL, however our hope is that many of the underlying insights will be of great use for the III-nitride VCSELs community as a whole. Throughout this report, we have taken great effort to highlight the future research fronts that would advance the field of III-nitride VCSELs generally, with the goal of illuminating the path forward for achieving efficient CW operating III-nitride VCSELs.</p>

<p> Breast cancer is one of the most common cancers in women with a very high incident rate, especially for those women who are between 40-60 years old. Most drugs are large or non-polar macromolecules, which cannot get into cancer cells autonomously, so a method that can deliver those drugs is very important. Optoporation method has been facilitated with gold nanoparticles, which are bound to breast cancer cells, and then absorb the optical energy to improve the membrane permeabilization. Long-term dietary consumption of fruits and vegetables high in &beta;-carotene and other phytochemicals has been shown beneficial in terms of anti-cancer, anti-aging, preventing cardiovascular disease and cataract. However they are large non-polar molecules that are difficult to enter the cancer cells. Here in this study, we applied optoporation method by using &beta;-carotene, and tetracycline as anti-cancer drugs in various concentrations to optimize highest selective cell death/best potential for T47D breast cancer cell lines.</p>

<p> Collagen is the main component of human connective tissue and extracellular matrix. Here we report multiple novel methods for utilizing optical tweezers to measure mechanical properties of different hierarchical levels of collagenous materials. First, we introduce a method for optical trap calibration that is suitable for viscoelastic material. The method is designed for use on experimental setups with two optical tweezers and is based on pulling a trapped particle with one trap while holding it with the other. The method combines advantages of commonly known PSD-fitting and fast-sweeping methods, allowing calibration of a completely fixed trap in a fluid of unknown viscosity/viscoelasticity without additional expensive equipment. Then we report an approach to measure the longitudinal component of the elastic moduli of biological fibers under conditions close to those found <i>in vivo</i> and apply it to type I collagen from rat tail tendon. This approach combines optical tweezers, atomic force microscopy, and exploits Euler-Bernoulli elasticity theory for data analysis. The approach also avoids the traditional drying-soaking cycle, since samples are freshly extracted. Importantly, strains are kept below 0.5%, which appear consistent with the linear elastic regime. We find, surprisingly, that the longitudinal elastic modulus of type I collagen cannot be represented by a single quantity but rather is a distribution that is broader than the uncertainty of our experimental technique. Lastly, we report a new method for characterizing anisotropic viscoelastic response of collagenous matrices. Anisotropic collagenous extracellular matrices are used in biomedicine to enhance the wound healing process by directing fibroblast proliferation. We utilize an optical trap to monitor the thermal fluctuations of microspheres embedded into collagenous network to extract a viscoelastic response function of the network along the principal axes of anisotropy.</p>

<p> This dissertation concerns the fabrication, analysis, and simulation of computer generated geometric phase holograms (CGHs). The current knowledge of CGHs is advanced to enable the creation of new sophisticated optical elements with unique characteristics. These elements enable new technologies related to displays, astronomy, sensing, beam-steering, beam-shaping, and more.</p><p> First, a novel direct-write system for CGH creation is presented. A mathematical description of the system is developed which allows the result of a given scan pattern to be predicted. The accuracy of the model is validated with various scan patterns, then a high-quality direct-write polarization grating and q-plate are fabricated for the first time.</p><p> With a system capable of creating CGHs, the most common and useful CGHs are explored in depth: the polarization grating, the geometric phase lens, and the Fourier geometric phase hologram. For each element, the possible scan patterns and parameters and their effect on the resulting element's quality are studied. Ultimately, the optimal scan patterns and parameters are found, then best-quality elements of each type are created and characterized. </p><p> Finally, a new tool for simulating periodic CGHs is developed. This begins with the derivation of the algorithm, which is based on the finite-difference time-domain (FDTD) method. Next tool's capabilities are verified by simulating many test structures and comparing the results to known solutions. The tool is used to simulate, for the first time, a CGH multiple beam splitter and a GPL array.</p>

<p> Analog RF-photonic links hold the potential to increase the precision of time and frequency synchronization in commercial applications by orders of magnitude. However, current RF-photonic links that are used for synchronization must suppress optical-fiber-induced noise by using bi-directional active feedback schemes, in which light must travel through the optical fiber in both directions. These schemes are incompatible with most existing fiber-optic networks. Unless this noise can be suppressed using different methods, RF-photonic time and frequency synchronization will remain accessible only to the research community. As a first step towards identifying alternate means of suppressing the optical-fiber-induced noise, this dissertation presents an extensive experimental characterization and limited theoretical discussion of the dominant optical-intensity and RF-phase noise source in a laboratory setting, where environmental fluctuations are small. The experimental results indicate that the optical-fiber-induced RF-phase noise and optical-intensity noise are caused by the same physical mechanism. The experimental results demonstrate that this mechanism is related to the laser-phase noise but not the laser intensity noise. The bandwidth of the optical-fiber-induced noise depends on the optical-fiber length for lasers with low phase noise, while for lasers with high phase noise, the bandwidth is constant. I demonstrate that the optical-intensity and RF-phase noise can be mitigated by dithering the laser frequency. Based on these results, I hypothesize that interference from Rayleigh scattering is the underlying mechanism of the optical-intensity and RF-phase noise. Prior theoretical work, carried out with high phase noise lasers, predicts that the noise induced by this process will have a bandwidth that is proportional to the laser linewidth and that is constant with respect to the optical-fiber length, for lasers with high-phase noise, which is consistent with the experimental results. I derive a simple model that is valid for low-phase-noise lasers. I compare this model with the experimental results and find that it matches the optical-fiber-length-dependent bandwidth that is measured for low-phase-noise lasers.</p>

Thesis (Ph. D.)--Syracuse University, 2005. / "Publication number AAT 3193856."

<p> In this dissertation, the development of alternative fiber based polishing tools for the finishing of precision freeform and aspherical optics is introduced. Freeform and aspherical optics, i.e. optics with varying radius of curvatures (ROC), are the current forefront for solutions for modern optical systems, enabling more compact and higher performance designs than possible with systems composed of classical optical components, i.e. planar and spherical optics. The technological challenges associated with the fabrication of freeform optics include; (1) identification of suitable tooling capable of accommodating the different ROC&rsquo;s, and (2) achieving surfaces with low mid spatial frequency (MSF) error content. The mainstream fabrication techniques for freeform optics heavily rely on a process called sub-aperture polishing, whereby a tool (down to 1/10^th of the optic size), is programmatically traversed across the surface to finish the part. This technique, due to the remnant tool path marks, results in MSF errors on the optic&rsquo;s surface. Removal of MSF errors is an ongoing challenge in the optics industry. As the main contribution of this work, it will be shown that fiber based tools, which have the flexibility to conform to varying ROCs, have the potential to remove preexisting MSF errors. The other contributions of this work are as follows: (1) Favorable fiber characteristics for use in the proposed fiber based tools are isolated. (2) The material removal mechanism associated with fiber based tools is described. (3) Finite element models (FEM) are created to gain insights on the fundamental fiber-workpiece interaction, and on the fiber properties and geometries most suited for MSF reduction. (4) The initial steps of implementing fiber based tools in commercial, multi axis optic finishing machines are completed and the associated challenges identified.</p><p> In summary, this work lays the foundation for using fiber based tools to reduce MSF&rsquo;s on freeform surfaces, and in doing so, the work addresses a critical need as identified by the optical fabrication community.</p><p>

<p> Space division multiplexing (SDM) has become a promising approach in the telecom industry to reduce the cost-per-bit of optical fiber transmission and to resolve the approaching bandwidth crunch. Meanwhile, intermodal nonlinear effects in few-mode fibers (FMF) potentially provide some novel applications along with sophisticated optical signal processing functionality. Recently, such spatial channels and modes have been applied in optical sensing applications with the returned echo analyzed for the collection of essential environmental information. The key advantages of implementing SDM techniques in optical measurement systems include the multi-parameter discriminative capability and accuracy improvement. In this dissertation, we conduct theoretical and experimental study on the SDM systems using FMFs for both optical transmission and sensing applications. </p><p> We first investigate a fast-convergence single-stage adaptive frequency-domain recursive-least-square algorithm for simultaneously compensating chromatic dispersion and differential mode group delay in a 224 Gbit/s six-mode polarization-division multiplexed 16 quadrature amplitude modulation FMF transmission system, which increases convergence speed by 53.7% over conventional frequency-domain least-mean square method, with 11% hardware complexity reduction over two-stage recursive-least square approach. </p><p> We then present an ultrafast all-optical simultaneous wavelength and mode conversion scheme based on intermodal four-wave mixing, with the capability of switching polarization and mode degeneracy orientation in FMFs. The relation among the conversion efficiency, pump power and phase matching conditions is investigated in theory analysis and simulation. The cross-polarization modulation and cross-mode modulation can be achieved, by in the best case up to 50% conversion efficiency. </p><p> Finally, a single-end FMF-based distributed sensing system that supports simultaneous temperature and strain monitoring is demonstrated via Brillouin optical time-domain reflectometry and heterodyne detection. Theoretical analysis and experimental assessment of multi-parameter discriminative measurement applied to the distributed sensors are presented, which endows with good sensitivity characteristics and can prevent catastrophic failure in many applications.</p><p>