title: Stimulated Raman gas sensing by backward UV lasing from a femtosecond filament.
abstract: We perform a proof-of-principle demonstration of chemically specific standoff gas sensing, in which a coherent stimulated Raman signal is detected in the direction anticollinear to a two-color laser excitation beam traversing the target volume. The proposed geometry is intrinsically free space as it does not involve back-scattering (reflection) of the signal or excitation beams at or behind the target. A beam carrying an intense mid-IR femtosecond (fs) pulse and a parametrically generated picosecond (ps) UV Stokes pulse is fired in the forward direction. A fs filament, produced by the intense mid-IR pulse, emits a backward-propagating narrowband ps laser pulse at the 337 and 357 nm transitions of excited molecular nitrogen, thus supplying a counter-propagating Raman pump pulse. The scheme is linearly sensitive to species concentration and provides both transverse and longitudinal spatial resolution.
authors.forename: P N
authors.initials: PN
authors.lastname: Malevich
authors.forename: R
authors.initials: R
authors.lastname: Maurer
authors.forename: D
authors.initials: D
authors.lastname: Kartashov
authors.forename: S
authors.initials: S
authors.lastname: Ališauskas
authors.forename: A A
authors.initials: AA
authors.lastname: Lanin
authors.forename: A M
authors.initials: AM
authors.lastname: Zheltikov
authors.forename: M
authors.initials: M
authors.lastname: Marangoni
authors.forename: G
authors.initials: G
authors.lastname: Cerullo
authors.forename: A
authors.initials: A
authors.lastname: Baltuška
authors.forename: A
authors.initials: A
authors.lastname: Pugžlys