Biblio

Extended interaction oscillators (EIOs) are high-frequency vacuum-electronic sources, capable to generate millimeter-wave to terahertz (THz) radiations. They are considered to be potential sources of high-power submillimeter wavelengths. Different slow-wave structures and beam geometries are used for EIOs. This paper presents a quantitative figure of merit, the critical unloaded oscillating frequency (fcr) for any specific geometry of EIO. This figure is calculated and tested for 2π standing-wave modes (a common mode for EIOs) of two different slowwave structures (SWSs), one double-ridge SWS driven by a sheet electron beam and one ring-loaded waveguide driven by a cylindrical beam. The calculated fcrs are compared with particle-in-cell (PIC) results, showing an acceptable agreement. The derived fcr is calculated three to four orders of magnitude faster than the PIC solver. Generality of the method, its clear physical interpretation and computational rapidity, makes it a convenient approach to evaluate the high-frequency behavior of any specified EIO geometry. This allows to investigate the changes in geometry to attain higher frequencies at THz spectrum.

A spin-Hall nano-oscillator (SHNO) is a type of spintronic oscillator that shows promising performance as a nanoscale microwave source and for neuromorphic computing applications. Within such nanodevices, a non-ferromagnetic layer in the presence of an external magnetic field and a DC bias current generates an oscillating microwave voltage. For developing optimal nano-oscillators, accurate simulations of the device's complex behaviour are required before fabrication. This work simulates the key behaviour of a nanoconstriction SHNO as the applied DC bias current is varied. The current density and Oersted field of the device have been presented, the magnetisation oscillations have been clearly visualised in three dimensions and the spatial distribution of the active mode determined. These simulations allow designers a greater understanding and characterisation of the device's behaviour while also providing a means of comparison when experimental resultsO are generated.