Two-photon gain and lasing in strongly driven two-level atoms

Localization of a two-level atom via the absorption spectrum

“…It is well known that the strongly driven two-level system displays two absorption peaks and two gain peaks near the Rabi frequency sidebands. On the basis of such spectrum, amplification without population inversion [21] and dressed state two-photon lasers are achievable [22,23]. Here we use a standing-wave field as a driving field.…”

Sub-half-wavelength localization of a two-level atom via trichromatic phase manipulation

“…It is well known that a driven two-level atom is the most representative system, which is most widely used to explore quantum coherence effects. Recent examples include the selective elimination of the fluorescence spectral lines via a polychromatic field [43,52], two-photon lasing based on population inversion between dressed states [53,54], and ultraslow light propagation at room temperature [55]. Here, we show that the two-level atom can be localized within half wavelength by employing the quantum interference created by a trichromatic field.…”

Realization of a continuous-wave, two-photon optical laser

“…Recently, it has been demonstrated [6] that stronglydriven two-level atoms display two-photon gain, and it has been predicted [7] that this gain can, under reasonable experimental conditions, be useful in the realization of a two-photon laser. We report in this Letter on the use of a driven-atom gain medium to provide the first demonstration of cw two-photon Iasing in the optical regime.…”

“…We report in this Letter on the use of a driven-atom gain medium to provide the first demonstration of cw two-photon Iasing in the optical regime. The two-photon laser operates in the degenerate mode (both photons generated in the SE process have the same frequency) and displays dynamics that are dramatically different from those found in the case of normal onephoton-gain-based lasers.As discussed in detail elsewhere [6,7], the two-photon gain that arises in the driven two-level-atom system can be understood simply using the dressed-atom picture [8]. The dressed-atom energy eigenstates are shown in Fig.…”

“…As discussed in detail elsewhere [6,7], the two-photon gain that arises in the driven two-level-atom system can be understood simply using the dressed-atom picture [8]. The dressed-atom energy eigenstates are shown in Fig.…”