Prospects of matter wave amplification by optical pumping

摘要

We discuss the prospects for a class of laser-like sources of atoms where the stimulated accumulation of atoms in the fundamental mode of a matter wave resonator is achieved by optical pumping. Precooled atoms in an internal state a which is not affected by the resonator trapping potential are excited into a state e by means of laser light. Once the atom is in state e it decays into the electronic ground state g by means of spontaneous emission, thereby occupying one of the resonator modes v $EQ 0, 1, ... Neglecting reabsorption of the spontaneously emitted photon, the probability for a transition into mode v is proportional to 1 $PLU n$-v$/ (`gain'), where n$-v$/ is the number of atoms in mode v prior to the transition. Including linear losses this model shows threshold behavior in the fundamental mode v $EQ 0, mode competition and Poissonian atom statistics above threshold. We also analyze the `small-signal gain' including reabsorption of the spontaneously emitted photons. We demonstrate that the threshold for matter wave amplification can only be reached in small 3D resonators of linear size comparable to the wavelength of the spontaneous photon, or in resonators with effectively reduced dimensionality.