Forward, backward, and sideways lasing in atmospheric air*

Remote lasing in atmospheric air allows and improves large distance standoff sensing and diagnostics due to the directional coherent emission. This talk will first introduce the fundamentals of air lasing and demonstrate atmospheric lasing using two-photon excitation of the atomic species resulting from dissociation of the air molecules such as nitrogen, oxygen, and water. Using direct excitation of the atomic species already present in air, we present lasing in air from two- and three-photon excitation of krypton and argon, respectively. The coherent forward and backwards air lasing are studied, and the properties of the coherent emission is analyzed. Using cylindrical focusing air lasing can be achieved sideways, providing emission of coherent beams perpendicular to the pump beam, or at an arbitrary angle. We present results on sideways lasing from both molecular dissociating and from directly exciting atomic species. Air lasing is demonstrated to aid remote sensing of atomic and molecular species. The stimulated emission process following multi-photon excitation which allows for air lasing is prevalent when applying nonlinear optical diagnostics such as two-photon absorption laser induced fluorescence (TALIF) using short pulses and can be used for species detection in gases and plasmas.