The aim of this thesis is to establish a platform for implementing nanoscale plasmonic slot waveguide (PSW) devices that can interface with dielectric technology for hybrid silicon-plasmonic interconnect applications. For waveguide excitation, an orthogonal junction coupler that operates based on momentum matching is analyzed and then experimentally demonstrated to have coupling efficiency of 50 +/- 2 % between 450 nm wide silicon waveguide and 50 nm wide PSW across a 200 nm bandwidth. Next, for designing scalable optical components with multiple-input multiple-output capability and high fabrication tolerance, two dimensional PSW mesh structure that utilizes simultaneous power distribution and interference within a network of intersecting PSW junctions is introduced. Finally, a closed-form model for PSW mesh structures is derived by incorporating the characteristic impedance model into the scattering matrix formalism. The model can handle arbitrary combination of junctions and has less than 5 % discrepancy when compared to Finite-Difference Time-Domain results.

The aim of this thesis is to establish a platform for implementing nanoscale plasmonic slot waveguide (PSW) devices that can interface with dielectric technology for hybrid silicon-plasmonic interconnect applications. For waveguide excitation, an orthogonal junction coupler that operates based on momentum matching is analyzed and then experimentally demonstrated to have coupling efficiency of 50 +/- 2 % between 450 nm wide silicon waveguide and 50 nm wide PSW across a 200 nm bandwidth. Next, for designing scalable optical components with multiple-input multiple-output capability and high fabrication tolerance, two dimensional PSW mesh structure that utilizes simultaneous power distribution and interference within a network of intersecting PSW junctions is introduced. Finally, a closed-form model for PSW mesh structures is derived by incorporating the characteristic impedance model into the scattering matrix formalism. The model can handle arbitrary combination of junctions and has less than 5 % discrepancy when compared to Finite-Difference Time-Domain results.

No description available.

No description available.

Over the last decade, considerable research interest has peaked in realizing an efficient Terahertz (THz) waveguide for potential applications in imaging, sensing, and communications applications. Two of the promising candidates are the two-wire waveguide and the parallel-plate waveguide (PPWG). I present theoretical and experimental evidence that show that the two-wire waveguide supports low loss terahertz pulse propagation, and illustrate that the mode pattern at the end of the waveguide resembles that of a dipole. In comparison to the weakly guided Sommerfeld wave of a single wire waveguide, this two-wire structure exhibits much lower bending losses. I also observe that a commercial 300-Ohm two-wire TV-antenna cable can be used for guiding frequency components of up to 0.2 THz, although these cables are generally designed to operate only up to about 800 MHz. The parallel-plate waveguide is another promising candidate that would make an efficient THz waveguide, since it has relatively low Ohmic losses. The transverse electromagnetic mode (TEM) of this waveguide has been generally preferred since it has no cutoff frequency, and therefore no group velocity dispersion. Utilizing this TEM mode, I study the reflection of THz radiation at the end of a PPWG, due to the impedance mismatch between the propagating transverse-electromagnetic mode and the free-space background. I find that for a PPWG with uniformly spaced plates, the reflection coefficient at the output face increases as the plate separation decreases, consistent with predictions by early low frequency ray optical theory. I observe this same trend in tapered PPWGs, when the input separation is fixed, and the output separation is varied. In another study, I investigate how to minimize diffraction losses in PPWGs by using plates with slightly concave surfaces. Using a simple “bouncing plane wave” analysis, I demonstrate how to determine an ideal radius of curvature for a waveguide operating at a given THz frequency. I perform a detailed experimental and simulation study that illustrates, for a waveguide with a plate separation of 1 cm, one can inhibit the diffraction around a frequency of 0.1 THz, when the surface has a curvature of 6.7 cm. Using much longer PPWGs (about 170cm), I reliably measure the overall losses in a PPWG with a radius of curvature of R=6.7 cm, and find it to be less than 1db/m around the design frequency (of 0.1 THz). This is very close to the lowest achieved loss to date with any terahertz waveguide.

The results of cross polarized pump-probe experiments in preformed He plasma waveguides are reported. Pump and probe have same wavelength and duration of 800nm and 80fs respectively. Peak pump intensity is I[subscript guided] = 0.2X10¹⁸W/cm² ~1000 I[subscript probe]. Single shot probe spectra and mode profiles at the channel exit are discriminated from the pump with a polarization analyzer and captured at various relative time delays [Delta]t. Frequency-domain interference (FDI) between the probe and a weak depolarized component of the pump is observed for [scientific equation]. Although the depolarized component is nearly undetectable through measurement of pump leakage alone, FDI sensitively reveals its substantially non-Gaussian structure. The possible depolarization mechanisms are analyzed. When probe is positioned at the leading edge of the pump, [scientific equation], its spectrum suffers a blue shift not measurable in the transmitted pump itself. The evidence suggests the channel interior is fully ionized and the partially formed channel ends are the origin of both depolarization and blue shift. A robust, pulsed, differentially-pumped plasma channel generation cell for high intensity guiding experiments has been developed. The design includes an axicon lens, windows for transverse interferometry, and permits injection of one or two different gases (main gas plus high Z seed gas) with several millisecond injection times and simultaneous 0.1ms pressure sensing resolution. Very well formed plasma waveguides have been formed in helium as well as hydrogen, at repeatable and well controlled pressures up to 1000Torr, with very uniform interior density, rapid density drop at boundaries, and very low exterior density. The possible danger associated with the use of large amounts of hydrogen was considered and a complex safety system was designed, constructed and used. Extensive analysis of channel profile reconstruction through transverse interferometry was performed. This includes an intuitive, efficient reformulation and extension of the Phase Locked Loop (PLL) carrier fringe demodulation method. It is also demonstrated and explained how and under which conditions artificial fringe frequency multiplication can reduce demodulation distortions in both PLL and Fast Fourier Transform (FFT) methods. / text

<p>Waveguides are used to transmit electromagnetic signals.Their geometry is typically long and slender their particularshape can be used in the design of computational methods. Onlyspecial modes are transmitted and eigenvalue and eigenvectoranalysis becomes important.</p><p>We develop a .nite-element code for solving theelectromagnetic .eld problem in closed waveguides .lled withvarious materials. By discretizing the cross-section of thewaveguide into a number of triangles, an eigenvalue problem isderived. A general program based on Arnoldi’s method andARPACK has been written using node and edge elements toapproximate the .eld. A serious problem in the FEM was theoccurrence of spurious solution, that was due to impropermodeling of the null space of the curl operator. Therefore edgeelements has been chosen to remove non physical spurioussolutions that arises.</p><p>Numerical examples are given for homogeneous andinhomogeneous waveguides, in the homogeneous case the resultsare compared to analytical solutions and the right order ofconvergence is achieved. For the more complicated inhomogeneouswaveguides with and without striplines, comparison has beendone with results found in literature together with gridconvergence studies.</p><p>The code has been implemented to be used in an industrialenvironment, together with full 3-D time and frequency domainsolvers. The2-D simulations has been used as input for full3-D time domain simulations, and the results have been comparedto what an analytical input would give.</p>

No description available.

No description available.

by Ng Chi Shing. / Chinese title in romanization: Shao sheng bo zai deng li zi ti guan dao nei di fei fa san zhuan bo. / Thesis (M.Ph.)--Chinese University of Hong Kong, 1987. / Bibliography: leaf 70.