1. Field of the Invention
The present invention relates generally to apparatus for producing terahertz (THz) radiation. More specifically, the present invention relates to a microelectromechanical system (MEMS)-based reverse magnetron apparatus for producing THz radiation.
2. Description of the Related Art
Most current sources of THz radiation are either very dim (e.g. nonlinear down conversion of optical lasers generate typically nanowatt (nW) outputs), very inefficient, or both (e.g. far infrared lasers have a power output in the THz region of few milliwatts (mW) but efficiencies of about 0.01%). Such conventional THz radiation sources are described in P. H. Siegal, “THz Technology: An Overview”, International Journal of High Speed Electronics and Systems, Vol. 13, No. 2 (2003), which is herein incorporated by reference.
Quantum cascade lasers can be as bright as 50 mW, but they require cryogenic cooling. Unfortunately, other apparatus capable of generating intense sources of THz radiation are uniformly bulky and difficult to transport (e.g. free electron laser and synchrotron radiation sources).
Magnetrons have featured prominently in the production of intense microwave radiation, as described in, for example, Victor L. Granatstein and Igor Alexeff, ed., High Power Microwave Sources, Boston: Artech, 1987, herein incorporated by reference. While the external configurations of different conventional magnetrons vary, the basic internal structures are generally the same—these include a central filament/cathode, an outside anode cylinder concentric to the cathode, an antenna, and magnets. The motion of electrons is due to the combined influence of cross electric (radial) and magnetic (axial) fields. In this case, the radiation frequency is near to the cyclotron frequency and amplification is achieved as the whirling cloud of electrons, influenced by the high voltage and the strong magnetic field, forms a rotating pattern that resembles the spokes in a spinning wheel and interacts with an alternating current flow in the resonant cavities configured at the inner surface of the anode. In order to achieve radiation frequencies in the THz region, unrealistically large magnetic fields, of several Tesla, are required.
U.S. Pat. No. 7,274,147, issued to Shim et al., describes a MEMS-based apparatus, using a miniaturized magnetron and claims to generate THz radiation. In Shim et al. an anode block concentrically surrounds a cathode unit and the electrons spiral outward. The large magnetic field requirements for operation of this device in the THz region make this apparatus impractical.