title: Terahertz emission from ultrafast ionizing air in symmetry-broken laser fields.
abstract: A transient photocurrent model is developed to explain coherent terahertz emission from air irradiated by a symmetry-broken laser field composed of the fundamental and its second harmonic laser pulses. When the total laser field is asymmetric across individual optical cycles, a nonvanishing electron current surge can arise during optical field ionization of air, emitting a terahertz electromagnetic pulse. Terahertz power scalability is also investigated, and with optical pump energy of tens of millijoules per pulse, peak terahertz field strengths in excess of 150 kV/cm are routinely produced.
authors.affiliation: Los Alamos National Laboratory, Center for Integrated Nanotechnologies, Los Alamos, NM 87545, USA. kykim@lanl.gov
authors.forename: Ki-Yong
authors.initials: KY
authors.lastname: Kim
authors.forename: James H
authors.initials: JH
authors.lastname: Glownia
authors.forename: Antoinette J
authors.initials: AJ
authors.lastname: Taylor
authors.forename: George
authors.initials: G
authors.lastname: Rodriguez