  The need for molecular standoff detection has motivated the development of a
remotely pumped, high gain air laser that produces lasing in the backward
direction and can sample the air as the beam returns. High gain is achieved in
the near infrared following pumping with a focused ultraviolet laser. The
pumping mechanism is simultaneous resonant two-photon dissociation of molecular
oxygen and resonant two-photon pumping of the atomic oxygen fragments. The high
gain from the millimeter length focal zone leads to equally strong lasing in
the forward and backward directions. Further backward amplification is achieved
using prior laser spark dissociation.
