Patent ID: 7729403

Claim:
Apparatus for generation of coherent light by high-order harmonic generation (HHG) comprising: laser apparatus for providing coherent periodic optical pulses; electric discharge apparatus for generating pre-ionized plasma including; a capillary discharge tube formed of an insulating material; apparatus for supplying a gas at a desired pressure into the discharge tube; and circuitry to provide a periodically pulsed electric discharge across the gas for ionizing the atoms of the gas, wherein the periodically pulsed discharge leads the optical pulses by an interval, t; the circuitry including an anode electrode and a cathode electrode, the electrodes located at spaced apart openings on the capillary discharge tube; and optics for directing the optical pulses into the ionized gas; wherein the electric discharge apparatus pre-ionizes the gas sufficiently to allow the optical pulses to cause HHG in the pre-ionized gas, while reducing ionization-induced defocusing of the optical pulses.