Methods and apparatus for providing a broadband tunable source of coherent millimeter, sub-millimeter and infrared radiation utilizing a non-relativistic electron beam

Abstract

Techniques for super broadband operation of a long wavelength free-electron laser (FEL) on a non-relativistic electron beam are described. Because of the physical nature of the underlying instability, a frequency region within which amplification or generation of the electromagnetic waves occurs, ranges from frequencies slightly below to many times above the resonant FEL frequency. Therefore, in this regime, the device operating frequency is determined by the frequency characteristics of a device resonator and can be tuned over a wide range without changing the electron beam energy or wiggler period. The upper limit of the frequency band is imposed by the thermal spread in an electron beam. Although this regime cannot be understood (and, consequently, was not discovered) without using the relativistic equation of motion, the regime does not rely upon relativism of an electron beam. A non-relativistic implementation of this regime in a submillimeter/THz device is advantageously described.

I claim:  
     
         1 . A tunable electron device providing electromagnetic radiation at broad frequency operating ranges, the device comprising: 
 an electron gun injecting an electron beam to travel within a device interaction region in an axial direction;    a wiggler field system providing a first magnetic field causing the electron beam to travel in a helical trajectory along the axial direction;    an axial magnetic field system providing a second magnetic field in the direction opposite to the axial direction; and    a control system connected to the axial magnetic field system, electron gun, and wiggler field system, said control system causing parametric synchronism of the different eigen modes within the electron beam.    
     
     
         2 . The device of  claim 1 , wherein the electrons within the electron beam travel at non-relativistic velocity.  
     
     
         3 . The device of  claim 1 , wherein the eigen modes include cyclotron waves and space charge waves.  
     
     
         4 . The device of  claim 1 , wherein the control system controls the electron gun to provide constant beam energy while said device operates at varying output frequency ranges.  
     
     
         5 . The device of  claim 1 , wherein the control system controls the relative strengths of the first and second magnetic fields to vary the device's operating frequency.  
     
     
         6 . The device of  claim 1 , further comprising a device resonator to vary the device's operating frequency.