Two Photons from One

Cun‐Zheng Ning

We propose to make a two-photon laser based on intersubband (sublevel) transitions in semiconductor nanostructures. The advantages and feasibility of such a two-photon laser are analyzed in detail using the density matrix approach. Both one-photon and two-photon gains in a three subband quantum well structure are studied on the same footing to show how the two-photon gain can be maximized, while the competing one-photon gain is minimized. The results show that a sufficient two-photon gain can be achieved to overcome one-photon competition and the loss of a conventional semiconductor cavity, making intersubband transitions one of the very few feasible approaches to two-photon lasing.

M. Bertolotti

I Ashraf, A. H. Toor

We have developed a quantum theory of the micromaser for a pair of two-level atoms for the case of one- and two-photon transition coupling. We have studied the effect of co-operativity on the photon statistics for these systems for different coupling constant ratios. It is found that for equal coupling, our system of a two-atom, one-photon micromaser behaves like a double one-photon cascade micromaser. Similarly, for equal coupling, the photon statistics of the two-atom, two-photon micromaser reduces to that of a three-level, four-photon cascade micromaser.

Toshihiro Nakanishi, Hirokazu Kobayashi, Kazuhiko Sugiyama +1 more

For dissipation-free photon-photon interaction at the single photon level, we analyze one-photon transition and two-photon transition induced by photon pairs in three-level atoms using two-photon wavefunctions. We show that the two-photon absorption can be substantially enhanced by adjusting the time correlation of photon pairs. We study two typical cases: Gaussian wavefunction and rectangular wavefunction. In the latter, we find that under special conditions one-photon transition is completely suppressed while the high probability of two-photon transition is maintained.

Hans Kleinpoppen