Electromagnetically induced generation, gain in delayed wave mixing, and measuring coherent states using quantum-interference windows

A three-level atom interacting with classical electromagnetic fields is coh erently excited by a two-photon transition near resonance and subsequently makes a second transition driven at resonance by a weak ir field at the noi se level. Our calculation predicts generation of an electromagnetic field a t a third frequency in the uv from zero field. Calculations show a gain of the uv radiation with propagation through the medium, though the population s of the two levels involved are never inverted. Other calculations produce a pulsed amplifier, two-photon optical nutation, and free induction memory . An effective susceptibility is defined and its imaginary part is found to be a good indicator of mode specific absorption and emission by the atomic state, and its real part a good indicator of dispersion. These calculation s exemplify the possibility of coherent control over an atomic vapor and th e production of a superradient macroscopic ensemble of states in the retard ed frame for realistic parameters.