Under usual laboratory conditions the absorption of a beam of light by a dilute two-level medium depends on the intensity and spectrum of the incident light. If the incident photon flux is small compared to the decay rate of the absorber’s excited state, saturation effects can be neglected and only the spectrum of the light is important; thus, weak-field absorption depends only on the firstorder correlation function of the incident light. This result relies, however, on a requirement that the incident beam cross-section be much larger than the absorption cross-section of an atom. Then individual atoms act as low efficiency scatterers and the statistics of the scattering process is governed by the law of large numbers applied to many scattering sites. In contrast, if it is arranged that just one atom significantly absorbs (scatters) a beam of photons, correlation functions of the incident light beyond the first-order must be considered. For a beam that is focused within an absorption cross-section, we might naively predict that every photon will be scattered and none transmitted. In fact, even for a very weak beam there is a finite probability for two photons to arrive at the atom within the excited state lifetime, and in this event at least one of them will be transmitted (statistical saturation). In this paper we calculate the transmitted photon flux for a weak beam of photons focussed strongly onto a single, resonant two-state atom. We study the dependence of the transmitted flux on the statistics of the incident photons. Photon beams derived from sources of coherent, chaotic, squeezed, coherent-antibunched, and broadband-antibunched light are considered. our calculations are based on a recently developed theory of cascaded open systems,1,2 and serve to illustrate the usefulness of this theory.Under usual laboratory conditions the absorption of a beam of light by a dilute two-level medium depends on the intensity and spectrum of the incident light. If the incident photon flux is small compared to the decay rate of the absorber’s excited state, saturation effects can be neglected and only the spectrum of the light is important; thus, weak-field absorption depends only on the firstorder correlation function of the incident light. This result relies, however, on a requirement that the incident beam cross-section be much larger than the absorption cross-section of an atom. Then individual atoms act as low efficiency scatterers and the statistics of the scattering process is governed by the law of large numbers applied to many scattering sites. In contrast, if it is arranged that just one atom significantly absorbs (scatters) a beam of photons, correlation functions of the incident light beyond the first-order must be considered. For a beam that is focused within an absorption cross-section, we might naively predict that every photon will be scattered and none transmitted. In fact, even for a very weak beam there is a finite probability for two photons to arrive at the atom within the excited state lifetime, and in this event at least one of them will be transmitted (statistical saturation). In this paper we calculate the transmitted photon flux for a weak beam of photons focussed strongly onto a single, resonant two-state atom. We study the dependence of the transmitted flux on the statistics of the incident photons. Photon beams derived from sources of coherent, chaotic, squeezed, coherent-antibunched, and broadband-antibunched light are considered. our calculations are based on a recently developed theory of cascaded open systems,1,2 and serve to illustrate the usefulness of this theory.

Annual Meeting Optical Society of AmericaJan 1, 19932 citations

Theory of coherent two-photon absorption

NILOY KUMAR DUTTA

Physics Letters ANov 1, 19785 citations

Transfer of optical vortices in coherently prepared media

Hamid Reza Hamedi, Julius Ruseckas, Emmanuel Paspalakis +1 more

We consider transfer of optical vortices between laser pulses carrying orbital angular momentum in a cloud of cold atoms characterized by the $\mathrm{\ensuremath{\Lambda}}$ configuration of the atom-light coupling. The atoms are initially prepared in a coherent superposition of the lower levels, creating a so-called phaseonium medium. If a single vortex beam initially acts on one transition of the scheme, an extra laser beam is subsequently generated with the same vorticity as that of the incident vortex beam. The absorption of the incident probe beam takes place mostly at the beginning of the atomic medium within the absorption length. The losses disappear as the probe beam propagates deeper into the medium where the atoms are transferred to their dark states. The method is extended to a tripod atom-light coupling scheme and a more general ( $n+1$ )-level scheme containing $n$ ground states and one excited state, allowing for creation of multiple twisted light beams. We also analyze generation of composite optical vortices in the scheme using a superposition of two initial vortex beams and study lossless propagation of such composite vortices.We consider transfer of optical vortices between laser pulses carrying orbital angular momentum in a cloud of cold atoms characterized by the $\mathrm{\ensuremath{\Lambda}}$ configuration of the atom-light coupling. The atoms are initially prepared in a coherent superposition of the lower levels, creating a so-called phaseonium medium. If a single vortex beam initially acts on one transition of the scheme, an extra laser beam is subsequently generated with the same vorticity as that of the incident vortex beam. The absorption of the incident probe beam takes place mostly at the beginning of the atomic medium within the absorption length. The losses disappear as the probe beam propagates deeper into the medium where the atoms are transferred to their dark states. The method is extended to a tripod atom-light coupling scheme and a more general ($n+1$)-level scheme containing $n$ ground states and one excited state, allowing for creation of multiple twisted light beams. We also analyze generation of composite optical vortices in the scheme using a superposition of two initial vortex beams and study lossless propagation of such composite vortices.

arXiv:1811.10647Physical Review AMar 6, 201980 citations

Interaction of Coherent Radiation with Atoms

A. D. Gazazyan

Journal of Experimental and Theoretical PhysicsJun 1, 19671 citation

Coherent momentum transfer in helium by adiabatic passage

John Lawall, Mara Goff Prentiss

We have demonstrated a coherent beam splitter for metastable helium based on adiabatic passage. Light from a homemade LNA laser at 1.083 {mu} is used to excite the {sup 3}S{sub 1}-{sup 3}P{sub 0} transition in a highly collimated beam of metastable helium. The atoms are first optically pumped into the m=0 and m=-1 sublevels. These sublevels are two independent {open_quotes}dark{close_quotes} states from which no further absorption is possible. Population is transferred adiabatically from the m = -1 level to the m =+1 level by means of two partially overlapping laser beams. As well as absorbing 2{h_bar} of angular momentum from the radiation field, the atoms initially in the m = -1 sublevel acquire 2{h_bar}k of linear momentum via an absorption/stimulated emission process. The process can be repeated back to m = -1, and we have demonstrated 4{h_bar}k and 6{h_bar}k coherent momentum transfer using successive interactions regions. The population initially in the m = 0 sublevel is undeflected by the light.We have demonstrated a coherent beam splitter for metastable helium based on adiabatic passage. Light from a homemade LNA laser at 1.083 {mu} is used to excite the {sup 3}S{sub 1}-{sup 3}P{sub 0} transition in a highly collimated beam of metastable helium. The atoms are first optically pumped into the m=0 and m=-1 sublevels. These sublevels are two independent {open_quotes}dark{close_quotes} states from which no further absorption is possible. Population is transferred adiabatically from the m = -1 level to the m =+1 level by means of two partially overlapping laser beams. As well as absorbing 2{h_bar} of angular momentum from the radiation field, the atoms initially in the m = -1 sublevel acquire 2{h_bar}k of linear momentum via an absorption/stimulated emission process. The process can be repeated back to m = -1, and we have demonstrated 4{h_bar}k and 6{h_bar}k coherent momentum transfer using successive interactions regions. The population initially in the m = 0 sublevel is undeflected by the light.

Bulletin of the American Physical SocietyMay 1, 19930 citations

n+1

)-level scheme containing

n

ground states and one excited state, allowing for creation of multiple twisted light beams. We also analyze generation of composite optical vortices in the scheme using a superposition of two initial vortex beams and study lossless propagation of such composite vortices.