Patent ID: 7382861

Claim:
A method of generating energetic electromagnetic radiation, the method comprising, during each of a plurality of separated radiation intervals: injecting laser radiation of a given wavelength into an optical cavity that is characterized by a round-trip transit time (RTTT) for radiation of that given wavelength, wherein: at least some radiation intervals are defined by one or more optical macropulses, at least one optical macropulse gives rise to an associated circulating optical micropulse that is coherently reinforced by subsequent optical micropulses in the optical macropulse and the electric field amplitude of the circulating optical micropulse at any given position in the cavity reaches a maximum value during the radiation interval, at least one optical macropulse that gives rise to a circulating optical micropulse consists of a series of optical micropulses characterized in that the spacing between the start of one optical micropulse and the start of the next is sufficiently close to an exact integral multiple (including 1×) of the RTTT for radiation of the given wavelength to provide at least 50% spatial overlap between injected optical micropulses and the circulating optical micropulse given rise to by that optical macropulse, and the injected optical micropulses in that optical macropulse are within ±45° of optical phase with the circulating optical micropulse given rise to by that optical macropulse; focusing the circulating micropulse at an interaction region in the cavity so that when the electric field amplitude of the circulating optical micropulse is at or near its maximum value, the circulating optical micropulse provides an optical undulator field in the interaction region characterized by a normalized vector potential greater than 0.1; directing an electron beam that includes a series of electron micropulses toward the interaction region in the cavity; synchronizing at least some of the electron micropulses with the circulating optical micropulse in the cavity; and focusing the electron beam at the interaction region in the cavity so at least one electron micropulse interacts with the optical undulator field in the interaction region and generates electromagnetic radiation at an optical frequency higher than the laser radiation's optical frequency.