High gain atomic oxygen lasing in air

We demonstrate coherent light generation and propagation forwards and backwards from a remotely generated high gain region created in ambient air. A 100 ps ultraviolet laser pulse is tuned to a two-photon atomic oxygen resonance, resulting in simultaneous dissociation and excitation in the focal volume. The excitation laser excites the resulting atomic oxygen atoms over a millimeter long region. We measure the gain to be greater than 60 cm^-1 and observe near-diffraction limited propagation in the forward and backward directions. We present evidence of the coherent nature of the emission. The high optical gain and strong directionality opens new opportunities for the remote detection of trace species and provides greater range for stand-off detection capabilities.