While conventional lasers are based on gain media with three or four real levels, unconventional lasers including virtual levels and two-photon processes offer new opportunities. We study lasing that involves a two-photon process through a virtual lower level, which we realize in a cloud of cold ytterbium atoms that are magneto-optically trapped inside a cavity. We pump the atoms on the narrow $^{1}S_{0}\ensuremath{\leftrightarrow}^{3}P_{1}$ line and generate laser emission on the same transition. Lasing is verified by a threshold behavior of output power vs pump power and atom number, a flat ${g}^{(2)}$ -correlation function above threshold, and the polarization properties of the output. In the proposed lasing mechanism the trapping beams create the virtual lower level of the lasing transition. The laser process runs continuously, needs no further repumping, and might be adapted to other atoms or transitions such as the ultranarrow $^{1}S_{0}\ensuremath{\leftrightarrow}^{3}P_{0}$ clock transition in ytterbium.While conventional lasers are based on gain media with three or four real levels, unconventional lasers including virtual levels and two-photon processes offer new opportunities. We study lasing that involves a two-photon process through a virtual lower level, which we realize in a cloud of cold ytterbium atoms that are magneto-optically trapped inside a cavity. We pump the atoms on the narrow $^{1}S_{0}\ensuremath{\leftrightarrow}^{3}P_{1}$ line and generate laser emission on the same transition. Lasing is verified by a threshold behavior of output power vs pump power and atom number, a flat ${g}^{(2)}$-correlation function above threshold, and the polarization properties of the output. In the proposed lasing mechanism the trapping beams create the virtual lower level of the lasing transition. The laser process runs continuously, needs no further repumping, and might be adapted to other atoms or transitions such as the ultranarrow $^{1}S_{0}\ensuremath{\leftrightarrow}^{3}P_{0}$ clock transition in ytterbium.

arXiv:1711.08707Physical Review AJan 14, 201911 citations

Multiphoton emission spectrum of atoms in a cavity

Zhenfei Luo, Lei Xu, Zhizhan Xu

Physics Letters AApr 1, 19928 citations

Quantum interference due to energy shifts and its effect on spontaneous emission

Zheng-Hong Li, Dawei Wang, Hang Zheng +2 more

We study the quantum interference in spontaneous emission with the inclusion of counterrotating terms and energy shifts. The energy shifts come from the emission and then reabsorption of virtual photons as well as the real photon emission. We show that the quantum interference resulting from the energy shifts has significant influence on the effective decay rates of the two levels, even when the transition dipole elements are the same and the energy separation of the two levels is small. We also show that the energy shift has substantial influence on the spectrum emitted by the atom. The result is valid in the long time limit. The effect of the energy shift can be observed at the time scale of 1 over the atomic decay rate. We suggest an experiment to test the effect of quantum interference because of energy shifts on the emission spectrum.We study the quantum interference in spontaneous emission with the inclusion of counterrotating terms and energy shifts. The energy shifts come from the emission and then reabsorption of virtual photons as well as the real photon emission. We show that the quantum interference resulting from the energy shifts has significant influence on the effective decay rates of the two levels, even when the transition dipole elements are the same and the energy separation of the two levels is small. We also show that the energy shift has substantial influence on the spectrum emitted by the atom. The result is valid in the long time limit. The effect of the energy shift can be observed at the time scale of 1 over the atomic decay rate. We suggest an experiment to test the effect of quantum interference because of energy shifts on the emission spectrum.

Physical Review ANov 3, 201015 citations

Emission spectrum of a partially inverted atomic system in a cavity

H. M. Castro-Beltrán, S. M. Chumakov, J. J. Sánchez-Mondragón

Optics CommunicationsAug 1, 19964 citations

Effect of atomic cooperation on emission spectra of atoms in a cavity

Chin-lin Chai, Fuli Li, Zhi‐Ming Zhang

Physics Letters AOct 1, 19908 citations

Virtual transitions in an atom-mirror system in the presence of two scalar photons

Ashmita Das, Soham Sen, Sunandan Gangopadhyay

We examine the virtual transition of an atom-mirror system with the simultaneous emission of two scalar photons, where the atom and the mirror admit a relative acceleration between them. For the single photon emission, the literature [A. A. Svidzinsky et al., Phys. Rev. Lett. 121, 071301 (2018)] dictates that the transition probabilities of two individual systems, such as an atom accelerating with respect to the mirror and its reverse, turn out to be equivalent under the exchange of the frequencies of atom and the field. Addressing the observational merit of such excitation process, a detectable probability ($P\ensuremath{\sim}{10}^{\ensuremath{-}2}$) is also reported in the above literature. In the present manuscript our finding dictates that the simultaneous emission of dual photon instead of one, destroys the equivalence between the transition probabilities as reported in the above literature.We examine the virtual transition of an atom-mirror system with the simultaneous emission of two scalar photons, where the atom and the mirror admit a relative acceleration between them. For the single photon emission, the literature [A. A. Svidzinsky et al., Phys. Rev. Lett. 121, 071301 (2018)] dictates that the transition probabilities of two individual systems, such as an atom accelerating with respect to the mirror and its reverse, turn out to be equivalent under the exchange of the frequencies of atom and the field. Addressing the observational merit of such excitation process, a detectable probability ($P\ensuremath{\sim}{10}^{\ensuremath{-}2}$) is also reported in the above literature. In the present manuscript our finding dictates that the simultaneous emission of dual photon instead of one, destroys the equivalence between the transition probabilities as reported in the above literature.

arXiv:2208.12021Physical review. D/Physical review. D.Jan 17, 20238 citations

{g}^{(2)}

-correlation function above threshold, and the polarization properties of the output. In the proposed lasing mechanism the trapping beams create the virtual lower level of the lasing transition. The laser process runs continuously, needs no further repumping, and might be adapted to other atoms or transitions such as the ultranarrow $^{1}S_{0}\ensuremath{\leftrightarrow}^{3}P_{0}$ clock transition in ytterbium.