Two photon laser.
(1) A resonator mirror can be seen just to the right of the center of
the figure. The red colored rings are the wires used to generate the
magnetic field for orienting atoms. (2) An idealized energy level scheme
showing how two-photon lasers work. Two incident photons stimulate an
atom to emit new photons, for a total of four photons in the final state.
et al., Physical Review Letters, 14 May 2001
Physics News Update
to Physics News Graphics