title: Observation of the second-harmonic generation from relativistically quivering electrons in exciting laser wakefield.
abstract: The second-harmonic emission generated by the spatially asymmetric quivering electrons caused by the ponderomotive force was studied. The intensity of the second harmonic was proportional to the focused intensity of the pump pulse with the power of 1.8. This intensity dependence can be explained by the relativistic effect of the quivering electrons.
authors.affiliation: Center for Tsukuba Advanced Research Alliance, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Takahashi
authors.forename: Michiaki
authors.initials: M
authors.lastname: Mori
authors.forename: Noboru
authors.initials: N
authors.lastname: Yugami
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Nishida
authors.forename: Kiminori
authors.initials: K
authors.lastname: Kondo