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Comment: 3 pages, 1 figure, to be published in Int J Electron Commun
The high-speed photonic network industry, driven by the demands of enormous growth of network data traffic, has grown to be a multi-billion dollar entity. The availability of increased data traffic has come about due to the growth in bandwidth transmitted over optical fiber. This growth is primarily due to research in two areas—time-division-multiplexed (TDM), and wavelength-division-multiplexed (WDM) photonic network schemes. A key bottleneck in these high-speed photonic networks is the optical-electronic (OE) interface. Currently, multiple laser sources and/or multiple serial optoelectronic modulators are used to implement the OE interface in both photonic network schemes. In this thesis, an apparatus will be demonstrated that could act as a relatively simple OE interface for these high-speed photonic networks. ^ The optical system...
This research investigates the effects of filtered optical feedback on the nonlinear dynamics of a diode laser. Dynamics due to optical feedback have traditionally been considered unwanted phenomena in diode lasers, and hence something to be avoided. In recent years, it has become apparent that some of these dynamics can be useful for certain applications. The principal focus of this research is to develop and investigate a novel mechanism for controlling these dynamics via parameters that are external to the laser system. ^ It is shown that there are three regimes of interest for filtered optical feedback based on the filter bandwidth relative to laser parameters (relaxation oscillation frequency and external cavity mode spacing). The dynamical response of the laser is quite different in each of the three regimes. The moderate and n...
Adaptive interferometry uses a self-adaptive beam mixer instead of a passive beam mixer as conventional interferometry does. A photorefractive quantum well device acting as an adaptive beam mixer in a two-wave mixing geometry stabilizes the interferometric phase in the far field. Advantages of adaptive interferometry are explored in two kinds of biomedicine: adaptive optical coherence reflectometry for biomedical imaging and adaptive optical bio-compact (BioCD) disk for biosensing. ^ Adaptive Optical Coherent Domain Reflectometry (OCDR) used adaptive ultrafast pulse mixing as the coherent gate for OCDR for the first time. Studied homodyne signals from the adaptive pulse-mixing effect, as well as the sensitivity and noise by both experiments and simulations. Demonstrated the addition ability of laser based ultrasound detection of this...
We present the results of our study on coherent control of photoionization of atomic barium. Our study focused on the understanding of the controllability, especially due to the effect of the coherent interaction between the atomic system and the laser field. ^ The first half of the study investigates the mechanisms of the control behind the previously observed laser phase-insensitive product state control. The controllability of this excitation scheme, two-color two-photon resonantly enhanced excitation, was analyzed from two aspects, the role of ac Stark shift introduced by the strong laser field and the multi-pathway quantum mechanical interferences. We have analyzed the excitation scheme from the analysis of the photoelectron angular distribution measured using the excitation scheme and the monitoring of the intermediate state po...
Coherence-domain imaging has become a well-established biomedical imaging technique with a wide range of applications. The most mature technique of this class is optical coherence tomography, which uses rapid point-by-point scanning detection for signal demodulation and computed reconstruction. Another approach in coherence-domain imaging is holographic optical coherence imaging (HOCI) that permits a direct wide-field depth-gated imaging by acquiring en face images at a fixed depth inside scattering media without the need to scan. Two approaches have been used in the development of real-time HOCI system: photorefractive holography and digital holography. In previous approaches, image-domain holograms in photorefractive holography and Fresnel off-axis digital holograms in digital holography have been used. In this thesis, Fourier-domai...
There is a continuous effort to develop techniques for nanoscale feature definition below the diffraction limit. Nanolithography has been a key technique because of its precision and cost effective. A sub-wavelength hole in an opaque screen can be used to provide a small light source with the optical resolution beyond the diffraction limit in the near field. However, a nanometer-sized hole in circular or square shapes is plagued by low transmission and poor contrast. This drawback limits the nanoscale apertures from being employed in nanolithography applications. Ridge apertures in C, H and bowtie shapes, on the other hand, have been numerically and experimentally demonstrated to show the ability of achieving both enhanced light transmission and sub-wavelength optical resolution down to nanometer domain benefiting from the existence of...
Paired metallic nanoparticles can show a strong optical resonance that depends strongly upon particle geometry, the gap between adjacent particles, material parameters and electromagnetic polarization. These pairs, often called optical antennae, are able to locally produce enhanced electromagnetic fields along with increased light scattering. ^ Studying ordered particle pairs is fairly new to the community and the topic requires continued growth and development for advanced device applications. The presented research focuses around the development and characterization of nanoantenna arrays that operate in the visible and NIR portion of the spectrum. Our design takes advantage of the gap resonance between two quasi-elliptical gold particles with the gap parallel to the long axis. ^ Arrayed and individual optical antennae have been f...
We employ common-path phase quadrature interferometry to measure optical phase shifts produced by biomolecules on a solid substrate, and apply it in immunoassay applications. Common-path interferometry produces a local reference wave that shares the same optical path with the signal wave, making the system ultra stable to mechanical vibrations or motions. Phase quadrature interference converts optical phase modulation caused by biomolecules into an intensity shift that is measured in the far-field.^ Two interferometric detection schemes of biomolecules are developed. The first is spinning-disc interferometry – the BioCD, which uses a laser beam to scan across a spinning disc carrying biomolecules. High-speed scanning moves the detection frequency far from 1/f noise of the system, providing a 50 dB suppression of the noise floor compa...
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