Emission and Absorption of Photons in Quantum Transitions. Coherent States

V. V. Dodonov, Vladimir I. Man’ko, Olga V. Man’ko

Po Dong, Sing Hai Tang, Weining Man +1 more

We show that amplification without inversion (AWI) can be realized with two coherent driving lasers in a four-level atom. With the help of quantum-jump theory, two transition processes are found to contribute to the absorption or gain behaviour. It is explicitly shown that an asymmetry between the three-photon stimulated emission and the single-photon absorption process leads to AWI. Furthermore, it is demonstrated that AWI can occur in this model with or without quantum interference. The origin of AWI without interference is explained by introducing weights for dressed-state transitions. The asymmetry between the weights for a dressed-state transition in absorption and its counterpart in emission leads to the possibility of AWI.

Valentine I. Zakharov

The possibility of a practically total reduction of quantum photon fluctuations in cw laser radiation is discussed. This effect appears as a result of two-photon radiation absorption using a resonance transition in atoms excited from the ground state to the upper level, relaxing to the other states. For this case the possibility of induced two-photon emission is excluded, that is, the source of additional photon number fluctuations in a field mode.1 In this process the Fock states with the photon number n ≥ 2 are continuously reduced from the coherent state of the excited field. For the large time values of interaction the Fock states |n = 0 > and |n = 1> remain in the field. The effect of spin orientations of photons of the excited field on the quantum noise reduction process for the two-photon absorption by atoms on the transitions between the S → S and S → D terms is analyzed. The possibility of transformation of coherent and thermal fields (λ ≃ 6022 Å and λ = 5787 Å) into quasi-Fock states, as a result of its two-photon resonance absorption by Na homogeneous vapor, is considered.

V. Ernst

Thomas P. Pearsall

Huai‐Zhi Wu, Zhen‐Biao Yang, Shi‐Biao Zheng

We study the dynamics of a system composed of two coupled cavities, each interacting with a single Rydberg atom. The interplay between Rydberg-Rydberg interaction and photon hopping enables the transition of the atoms from the collective ground state to the double Rydberg excitation state by individually interacting with the optical normal modes and suppressing the upconversion process between them. The atomic transition is accompanied by the two-photon absorption and emission of the normal modes. Since the energy level structure of the atom-cavity system is photon number dependent there is only a pair of states being in the two-photon resonance. Therefore, the system can act as a quantum nonlinear absorption filter through the nonclassical quantum process, converting coherent light field into a nonclassical state. Meanwhile, the vacuum field in the cavity inspires the Rydberg atoms to simultaneously emit two photons into the normal mode, resulting in obvious emission enhancement of the mode.