Ultrafast electrical signals: Transmission on broadband guiding structures and transport in the resonant tunneling diode.

摘要

This dissertation documents the experimental study of the transmission of picosecond electrical signals as they propagate along planar guiding structures and as they are switched by double-barrier heterostructure diodes. Applying advances in the field of ultrafast optics to revolutionary techniques in the generation and measurement of short electrical transients, a large contribution has been made to the growing field of ultrafast electronics. The progress of this discipline, which is essential to the future progress of the communications and computer fields, has to be furthered by the investigation of sources of high-speed digital signals and the means of transmitting these signals.;An algorithm has been developed and used to model the propagation of picosecond and subpicosecond electrical signals on normal and superconducting planar transmission lines. Included in the computation of a complex propagation factor are geometry-dependent modal dispersion, the frequency-dependent attenuation and phase velocity that arise as a result of the electrode material, and polarization effects that are displayed by the substrate material. The results of calculations are presented along with a comparison to experimental data acquired through the use of an electro-optic sampling technique.;The effects of the modal dispersion of planar lines, the complex surface conductivity of superconductors, and the dipolar relaxation of substrates are demonstrated. The transient propagation characteristics of planar lines were found to include an increased rise time, increased pulse width, the introduction of ringing onto the waveform, and a novel "pulse sharpening.".;Additionally, an investigation into the switching speed of the double-barrier quantum well resonant-tunneling diode produced the first observation of picosecond bistable operation in this device and added necessary information to the understanding of its transport mechanisms. A rise time of less than 2 ps was measured for the resonant-tunneling diode, again using the electro-optic sampling technique. This is the fastest switching event yet observed for an electronic device.;These studies of extremely fast switches, as well as transmission lines that can, depending on their properties, distort or faithfully transmit the outputs from these switches, have demonstrated that appropriately designed electrical elements can compare with even the fastest all-optical systems. This alone indicates that the knowledge gained about them may be very useful for high-speed circuit and logic applications.