Compact tuneable microwave terahertz source

摘要

Recently, it has been suggested that the next generation of millimetre/terahertz wave devices should be the result of the combination of the virtues of vacuum tubes with solid-state microfabrication methods. Vacuum devices can be very efficient if what is called a depressed collector system is used, so much so that efficiencies as high as 40% are commonplace at microwave frequencies. In addition, the electron mobility is essentially infinite, whereas in a solid-state component, carrier mobility is a serious limitation and leads to device heating problems and reduced efficiency. On the other hand, solid-state fabrication methods lead to micron size accuracy, with good yields and the economy of mass production, so that it is now possible to construct the miniature vacuum electronic device components required for operation at very short wavelengths. In addition, electron guns manufactured in silicon are now available, and these operate at much lower temperatures and produce higher beam current densities than are achievable with conventional thermionic emitters. It has recently been proposed that a folded waveguide travelling wave tube could be constructed using silicon microfabrication technology. When configured as an oscillator this device could provide a high power (≫100mW), highly efficient (≫15%), reliable, compact and cheap source for the Terahertz Gap. This paper will present a comprehensive up to date on the current status of Liverpool John Moores University electromagnetic wave.