Laser-diode frequency control by resonant phase-conjugate reflection from an atomic vapor

We report our first results on the frequency control of an AlGaAs laser diode by resonant phase-conjugate reflection from an atomic rubidium vapor. When the electrical feedback technique is used, the Allan variance reaches a flicker floor such that sigma(y)(2)(tau) = 1.6 x 10(-19) tau(0) for tau > 1s. We also demonstrate that laser frequency locking can be achieved by using the phase-conjugate reflection directly as a resonant optical feedback. This approach leads to a self-controlled optical frequency standard at 780 nm.