A model for an atom laser

Nicholas P. Robins, Craig M. Savage, Elena A. Ostrovskaya

Howard M. Wiseman

An atom laser is a hypothetical device which would produce an atomic field analogous to the electromagnetic field of a photon laser. Here I argue that for this analogy to be meaningful it is necessary to have a precise definition of a laser which applies equally to photon or atom lasers. The definition I propose is based upon the principle that the output of a laser is well-approximated by a classical wave of fixed intensity and phase. This principle yields four quantitative conditions which the output of a device must satisfy in order for that device to be considered a laser. While explaining these requirements, I analyse the similarities and differences between atom and photon lasers. I show how these conditions are satisfied first by an idealized photon laser model, and then by a more generic model which can apply to atom lasers also. Lastly, I briefly discuss the current proposals for atom lasers and whether they could be true lasers.

R. J. Ballagh, Craig M. Savage

Howard M. Wiseman

An atom laser is an as-yet unrealized device that would produce an atomic field analogous to the electromagnetic field of a photon laser. Here I argue that for this analogy to be meaningful it is necessary to have a precise definition of a laser that applies equally to photon or atom (or any other boson) lasers. The definition I propose uses the fundamental principle that the output of a laser is well approximated by a classical wave of fixed intensity and phase. This principle yields four quantitative conditions that the output of a device must satisfy in order for the device to be considered a laser. While explaining these requirements, I analyze the similarities and differences between atom and photon lasers. I next show how these conditions are satisfied first by an idealized photon laser model, and then by a more general model that can apply to atom lasers also. Lastly, I briefly discuss the current proposals for atom lasers and whether they could be true lasers.

Nicholas P. Robins, C. Figl, Matthew Jeppesen +2 more

Howard M. Wiseman, Ana María Guerra Martins, Daniel F. Walls

An atom laser is a device which would ideally produce a coherent excitation of a single mode of the Bose-atom field. That is to say, an atom laser field would have a well defined number of atoms, and a slow rate of phase diffusion. Here we consider an atom laser model recently proposed by Holland et al, based on evaporative cooling of atoms. We extend their model, and give approximate analytical results for the time-dependent intensity and phase statistics of the atom laser in different regimes. Although the intensity fluctuations may be relatively small, the laser linewidth is always in excess of the bare linewidth of the laser mode. Nevertheless, in one regime (weak collisions), the laser linewidth may be less than the output flux of atoms, which is a minimum requirement for considering the output to be coherent.