Apparatus and methods for generating and enhancing Smith-Purcell radiation

An apparatus for generating Smith-Purcell radiation having a spectral component at a wavelength λ, the apparatus comprising:

• a periodic structure comprising a dielectric material;
• and
• an electron source, in electromagnetic communication with the periodic structure, to emit an electron beam propagating within about 5λ from a surface of the periodic structure to induce emission of the Smith-Purcell radiation, the electron beam having an electron energy tunable between about 0.5 keV and about 40 keV so as to change the wavelength of the Smith-Purcell radiation,
• wherein the periodic structure comprises a two-dimensional (2D) photonic crystal characterized by a first dispersion line and the electron beam is characterized by a second dispersion line overlapping with at least a portion of the first dispersion line so as to generate the Smith-Purcell radiation with a bandwidth BW=av/c, where a is a period of the periodic structure, v is a speed of the electron beam, and c is the speed of light.

A method for generating Smith-Purcell radiation having a spectral component at a wavelength λ, the method comprising:

• generating an electron beam using a gated field emitter array (FEA) fabricated in a semiconductor substrate;
• propagating the electron beam within about 5λ from a surface of a periodic structure comprising a dielectric material and fabricated in the semiconductor substrate, the electron beam inducing emission of the Smith-Purcell radiation;
• and
• changing an electron energy of the electron beam between about 0.5 keV and about 40 keV to change a wavelength of the Smith-Purcell radiation.

A method for generating Smith-Purcell radiation having a spectral component at a wavelength λ, the method comprising:

• emitting an electron beam to propagate within about 5λ from a surface of a periodic structure comprising a dielectric material, the electron beam inducing emission of the Smith-Purcell radiation;
• and
• changing an electron energy of the electron beam between about 0.5 keV and about 40 keV to change a wavelength of the Smith-Purcell radiation,
• wherein emitting the electron beam comprises propagating the electron beam near the surface of a two-dimensional (2D) photonic crystal characterized by a first dispersion line, and the electron beam is characterized by a second dispersion line overlapping with at least a portion of the first dispersion line so as to generate the Smith-Purcell radiation having a bandwidth BW =av/c, where a is a period of the periodic structure, v is a speed of the electron beam, and c is speed of light.

A method for generating Smith-Purcell radiation having a spectral component at a wavelength λ, the method comprising:

• emitting an electron beam to propagate within about 5λ from a surface of a periodic structure comprising a dielectric material, the electron beam inducing emission of the Smith-Purcell radiation;
• and
• changing an electron energy of the electron beam between about 0.5 keV and about 40 keV to change a wavelength of the Smith-Purcell radiation,
• wherein the periodic structure comprises a two-dimensional (2D) photonic crystal characterized by a photonic band structure having a flat band and the electron beam is characterized by a dispersion line overlapping with at least a portion of the flat band so as to generate supercollimation.