This thesis presents a simulation and experimental study of a true time-delay (TTD) beamforming network using a Bragg grating prism on Ge-doped silica-on-silicon planar integrated optical waveguide for application in phased array antennas (PAA). The Bragg grating prism is designed and fabricated on planar optical waveguides and the true time-delay beamforming module is implemented using the fabricated waveguide Bragg grating prism and other photonic components. When dealing with a remotely controlled PAA, the dispersive properties of a standard single mode fiber must be taken under consideration. To this effect, a simulation study has been carried out and is detailed in this thesis. The Bragg grating prism used in the beamformer is composed of chirped gratings of different lengths but of same total chirp in order to produce a true time-delay progression. Two modulation techniques are considered, single sideband (SSB) and double sideband (DSB) modulation. SSB modulation is shown to be well suited for broadband operations with little impact on the orientation of the mainlobe resulting from chromatic dispersion. (Abstract shortened by UMI.)

An investigation of mode-locked fiber ring lasers and their applications in photonic generation of microwave signals is presented in this thesis. Both passive mode locking and active mode locking are investigated. For the passive mode-locking, a fiber laser with figure-eight structure that incorporates a nonlinear amplifying loop mirror as a saturable absorber is proposed and demonstrated. One application of the demonstrated passively mode locked fiber ring laser is to generate high-quality microwave signals. In this thesis, a microwave signal generated by beating the mode-locked longitudinal modes at a photodetector is realized. The results show that the generated microwave signal has low phase noise with high stability. Multiwavelength mode locked laser can find many applications in optical communications. In this thesis, a multiwavelength passively mode-locked fiber ring laser using cascaded fiber Bragg gratings is proposed and demonstrated. It is different from multiwavelength active mode locking in which the round-trip frequencies for all wavelengths must be identical; for passive mode locking, it is demonstrated theoretically and experimentally that the round-trip frequencies are not necessarily identical. A three-wavelength fiber ring laser that is passively mode locked with non-identical round-trip frequencies is demonstrated. (Abstract shortened by UMI.)

This thesis studies the characterization and simulation of long wavelength indium aluminium gallium arsenide (InAlGaAs) lattice-matched to indium phosphide (InP) diode laser, emitting between 1.648 to 1.7 mum in wavelength. The active region of one laser diode sample consists of six In0.69Ga 0.31As quantum wells (1.0% compressive strain) and seven In0.52 Al0.36Ga0.12As unstrained barriers. The lasers are grown using digital alloy molecular beam epitaxy (MBE). The band diagram analysis shows a large conduction band offset which is typical of InAlGaAs lasers. The geometry-dependent and temperature-dependent measurement as well as the laser optical gain, loss and spectral properties were carried out and comparison done for different ridge widths (1.2 to 2.8mum), cavity lengths (555 to 2200mum) and temperature range between 25 and 70°C. The output power as a function of current characteristics reveals threshold current increase with cavity lengths and ridge widths with thermal roll-off occurring at higher injection currents. The slope efficiency and external differential quantum efficiency increases for the narrowest and widest ridge widths within the same cavity length laser device but decreases with increase in cavity length. The temperature analysis shows longer cavity length lasers exhibit better temperature characteristic than the shorter cavity length laser devices indicating the better thermal stability of the longer cavity lasers. Temperature elevations also caused increase in threshold current and decrease in efficiencies. The temperature distribution shows a higher temperature in the active region than the operating temperature due to self heating of the laser devices in continuous wave operation. The optical spectrum exhibits red-shifting of the emission wavelength with increasing bias current and temperature.

In situ Raman spectroscopy was used to track the growth of carbon nanotubes grown by chemical vapor deposition. The dynamic evolution of three kinds of Raman bands, namely the G, D, and RBM bands, was analyzed. The evolution of nanotube diameter and crystallinity was analyzed from the RBM and D/G band evolution, respectively. A characteristic growth sequence consisting of four distinct stages of growth was consistently observed. The growth rate of each stage was found to decrease with increasing temperature, possibly due to parasitic, competing reactions, and energy scales for each stage are extracted. The evolution and nanotube distribution of samples grown with and without alumina support layers is contrasted and the role of alumina is discussed.

The minimum spacing of a plasma waveguide was calculated and applied to the formation of periodic nanocracks. The minimum spacing decreased with decreasing plasma frequency but was found to have limited effect on the spacing of the nanocracks. An extension to a standard Finite-Difference Time-Domain method was created to include nonlinear processes and the dynamic build up of the electron plasma. The ionized area produced in the simulation agrees with experiment. The existence of a self-limited absorption effect on a Gaussian pulse in time was verified in the simulations. The region was elongated along the direction parallel to the polarization of the light. The multiphoton absorption was found to be the main cause of the distinct shape of the damaged area. Plasma dispersion and self-focusing create larger electron densities and a shift in the location of the electron density peak, but did not affect the general shape.

This thesis presents a theoretical and experimental study of optical phase modulation and its applications in all-optical microwave signal processing, which include all-optical microwave filtering, all-optical microwave mixing, optical code-division multiple-access (CDMA) coding, and ultrawideband (UWB) signal generation. All-optical microwave signal processing can be considered as the use of opto-electronic devices and systems to process microwave signals in the optical domain, which provides several significant advantages such as low loss, low dispersion, light weight, high time bandwidth products, and immunity to electromagnetic interference. In conventional approaches, the intensity of an optical carrier is modulated by a microwave signal based on direct modulation or external modulation. The intensity-modulated optical signal is then fed to a photonic circuit or system to achieve specific signal processing functionalities. The microwave signal being processed is usually obtained based on direct detection, i.e., an opto-electronic conversion by use of a photodiode. In this thesis, the research efforts are focused on the optical phase modulation and its applications in all-optical microwave signal processing. To avoid using coherent detection which is complicated and costly, simple and effective phase modulation to intensity modulation (PM-IM) conversion schemes are pursued. Based on a theoretical study of optical phase modulation, two approaches to achieving PM-IM conversions are proposed. In the first approach, the use of chromatic dispersion induced by a dispersive device to alter the phase relationships among the sidebands and the optical carrier of a phase-modulated optical signal to realize PM-IM conversion is investigated. In the second approach, instead of using a dispersive device, the PM-IM conversion is realized based on optical frequency discrimination implemented using an optical filter. We show that the proposed PM-IM conversion schemes can be implemented by use of commercially available devices without increasing significantly the system complexity compared to IM-based systems. More importantly, the PM-IM conversions bring a number of very interesting features which would be used to implement different signal processing functionalities. First, the PM-IM conversion plus direct detection has a frequency response with a notch at the dc, this feature can be used to achieve all-optical microwave bandpass filtering. Second, in the PM-IM conversion based on frequency discrimination, the polarity of the detected electrical signal can be easily reversed by simply tuning the optical wavelength, which provides the possibility to achieve bipolar operation, a feature highly desirable and extremely important in all-optical microwave signal processing. In this thesis, the use of the PM-IM conversion features for all-optical signal processing is investigated. Specifically, (1) We propose and demonstrate three different filter architectures for all-optical microwave bandpass filtering. (2) We propose and demonstrate, for the first time, an all-optical microwave signal processor that can realize all-optical mixing and filtering simultaneously. (3) We propose and demonstrate a scheme to implement unipolar-bipolar phase-time encoding/decoding for optical CDMA. (4) UWB pulses are usually generated in the electrical domain for short-range high-data rate wireless communications. To extend its coverage, UWB signal distributed over optical fiber is a topic of interest recently. In the thesis, we propose and demonstrate two approaches to generating and distributing UWB pulses in the optical domain.

A prototype proton-cone-beam-computed-tomography (PCB-CT) system utilizing a proton radiatiotherapy beam has been developed. The system acquires CT data in the cone-beam geometry. The cone-beam is produced by scattering a 158.6 MeV narrow parallel proton beam on a range modifier in the form of a linear modulating wheel. The wheel is a PMMA propeller of variable thickness that rotates about its axis parallel to the beam line. The energy spectrum generated by the wheel is designed to result in a monotonically decreasing linear signal versus energy deposited in the detector system. Protons are detected by a system using an intensifying screen and CCD digital camera. The PCB-CT scanner measures relative stopping power of protons in 3D with equal resolution in each dimension. It operates at clinically relevant energies and geometries and in this way facilitates proton therapy planning techniques. The Feldkamp-Davis-Kress cone-beam reconstruction algorithm is applied to obtain the proton stopping powers. Calibration of the proton CT projections is performed with the aid of a stack of PMMA plates positioned in front of the intensifying screen. Contrast and spatial resolution of the PCB-CT scan is evaluated from CT reconstructions of a contrast-resolution phantom. Artifacts in the reconstruction due to neutron noise in the detector system are corrected by a subtraction technique. In addition, computer-simulations of proton CT projection data have been performed. For this purpose, a macroscopic proton transport algorithm has been developed. The algorithm derives from the Boltzmann equation. Energy loss is modeled by using experimental energy-range tables for specific materials, while energy deposition is modeled by using a measured dependence of dose on depth in water (the Bragg curve) and the concept of water equivalent thickness (WET). Nuclear collisions are accounted for by the inclusion of the experimental Bragg curve data in water. The small-angle-approximation is assumed in treating the multiple Coulomb scattering (MCS). Limitations of the PCB-CT in characterizing the relative proton stopping power due to the MCS phenomena are examined. A method of removing the MCS artifacts from the projection data is employed to obtain more accurate reconstructed proton stopping powers.

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