title: Phase velocity nonuniformity-resulted beam patterns in difference frequency generation.
abstract: The evolution of the difference frequency generation between a planar pump wave and a focused signal wave has been numerically investigated in this paper. We show that, at the difference frequency wave, various beam patterns such as ring and moon-like, are resulted due to the nonuniform distribution of phase velocity in the focused signal wave. The subluminal and superluminal regions can be identified by the intersection of two generated beam profiles that correspond to a pair of phase-mismatches with equal value but opposite signs.
authors.affiliation: State Key Laboratory for Advanced Photonic Materials and Devices, Department of Optical Science and Engineering, Laboratory for Advanced Materials, Fudan University, Shanghai 200433, China.
authors.forename: Daquan
authors.initials: D
authors.lastname: Lu
authors.forename: Liejia
authors.initials: L
authors.lastname: Qian
authors.forename: Yongzhong
authors.initials: Y
authors.lastname: Li
authors.forename: Hua
authors.initials: H
authors.lastname: Yang
authors.forename: Heyuan
authors.initials: H
authors.lastname: Zhu
authors.forename: Dianyuan
authors.initials: D
authors.lastname: Fan