title: Enhanced harmonic generation by breaking the phase-matching symmetry.
abstract: We introduce two static methods to break the phase-matching symmetry in third harmonic generation with a focused Gaussian beam in the tight focusing limit, dramatically increasing the conversion efficiency and mode quality. Both rely on inhibiting harmonic generation immediately after the beam waist, preventing the near perfect cancellation of the third harmonic generation (THG) from before and after the focus. The first method involves placing a thin metal septum at the waist: the laser drills a small pinhole, which, in turn, disrupts the beam focus after the pinhole. The second method is based on placing a large χ(3) gas before the focus and a small χ(3) gas after the focus.
authors.affiliation: Department of Physics, University of Connecticut, Storrs, Connecticut 06269, USA. gibson@phys.uconn.edu
authors.forename: G N
authors.initials: GN
authors.lastname: Gibson
authors.forename: N
authors.initials: N
authors.lastname: Majtenyi
authors.forename: E
authors.initials: E
authors.lastname: Sergan