Rate equations for multi-photon excitation in strong fields

András Dombi, András Vukics, P. Domokos

In the strong coupling regime of cavity QED where the characteristic damping rates are orders of magnitude below the coherent coupling, resolved multi-photon resonances can be observed for strong enough driving strength. In a certain frequency range, the external coherent drive field hits multi-photon resonances which correspond to very high order transitions that cannot be excited at the given power of the driving field. We found that in this range the cavity field evolves into a robust semiclassical solution which is the mixture of the vacuum and an excited quasi-classical state. The system is reminiscent of optical bistability, however, here a single atom produces a telegraph signal for the outgoing intensity by switching between two states with large photon number difference. We calculate this behavior also for the Tavis-Cummings model representing three qubits in an existing circuit QED experimental setting.

Asko Valli, Stig Stenholm

Moorad Alexanian, S. Bose

Kikuo Ujihara, L. Allen

The effect of amplitude and phase fluctuations on N-photon excitation from N independent lasers is investigated. Each laser is assumed to have a multi-lorentzian line shape. The Fokker-Planck equation is solved to yield atomic density matrix equations which incorporate the fluctuations. Most of the results discussed are for the lowest-order approximation. No enhancement in the Rabi frequency or transition probability appears, but the Stark shift is found to be enhanced by a factor which is independent of the degree of non-linearity of the process. A general expression for the transition probability in the rate equation regime is presented and its characteristic features discussed. The difference between N-photon excitation from N independent lasers and from a single laser is examined.

P. Lambropoulos, A. Lyras, Xian Tang

Xiaobo Chen, Guojian Yang, Li Song +5 more

The infrared quantum cutting phenomena, which is an international hot research field, of Er1.0P5O14 noncrystalline glass are studied by the present paper for the first time. The 1537.0nm infrared fluorescence of Er1.0P5O14 noncrystalline glass is confirmed to be the multi-photon quantum cutting fluorescence by computation and comparison between absorption and excitation spectra. It is found that the 4I13/2→4I15/2 quantum cutting fluorescence is very strong, induced by the excited 2H11/2, 4G11/2, and 4G9/2 energy levels. Its mechanism is thoroughly analyzed based on the calculation of spontaneous emission rates, nonradiative multiphonon relaxation rates and energy transfer rates. It is found the strong downconversion energy transfers {2H11/2→4I9/2,4I15/2→4I13/2},{4G11/2→4I13/2, 4I15/2→2H11/2},{4G9/2→4F7/2,4I15/2→4I13/2} 和 {4G9/2→4I13/2, 4I15/2→2H11/2} are responsible for the strong infrared three-photon and four-photon quantum cutting fluorescence of Er1.0P5O14 noncrystalline glass. The present research is significant for enhancing solar cell efficiency.