Phase-sensitive amplification in a three-level atomic system

Abstract

A linear theory of two-photon amplification by three-level atoms in the cascade configuration is developed, where a coherence is induced between the top and bottom levels, by an external classical driving field. It is shown that this system becomes an ideal parametric amplifier for sufficiently strong driving field, whereas for a weak driving field it is a phase-insensitive amplifier. In between these two extremes, one finds phase-sensitive amplification as well as squeezing for a certain range. The system does not, however, reduce to a model studied previously where the atomic coherence was treated as an initial condition. The system is also studied in a cavity configuration: It is predicted that the oscillator may behave as a two-photon correlated emission laser, i.e. , its phase diffusion coefficient vanishes.

Effect of biased noise fluctuations on the output radiation of coherent beat laser

“…In recent years, interaction of three-level atoms with radiation has attracted a great deal of interest in relation to the strong correlation induced particularly during the cascading transitions [1][2][3][4][5][6][7][8][9][10][11][12][13]. It is common knowledge by now that the atomic coherence in such a system is accountable for the squeezing of the emitted radiation.…”

“…In other words, the squeezing of the cavity radiation in particular is degraded since the vacuum field has fundamentally no definite phase. In this accord, various authors have studied similar scheme coupled to vacuum reservoir when the atomic coherence is induced by external driving radiation and when the atoms are initially prepared to be in the upper energy level [1], lower energy level [2] and arbitrary coherent superposition of the two levels. It has been argued that the three-level laser in these cases resemble the corresponding parametric oscillator in the strong driving limit.…”

“…It is common knowledge by now that the atomic coherence in such a system is accountable for the squeezing of the emitted radiation. The atomic coherence can be induced in a three-level cascade scheme by coupling the upper energy level |a and lower energy level |c, between which a direct transition is dipole forbidden, with external radiation [1][2][3][4][5][6] or by preparing the atom initially in coherent superposition of these two levels [7][8][9][10][11][12] or using these mechanisms at the same time [13]. In addition to these options, Xu and Hu [14] have considered the two-step cascade coherent excitation.…”

Coherently driven degenerate three-level laser with parametric amplifier

“…A three-level laser in which the top and bottom levels of the atoms injected into the cavity are coupled by a strong light has also been studied by different authors [7][8][9]. Ansari et al [9] have considered a degenerate three-level laser, with the atoms initially in the upper level and with the top and bottom levels of the atoms coupled by coherent light.…”

“…It has been established that a three-level laser under certain conditions generates squeezed light [1][2][3][4][5][6][7][8][9]. In a cascade three-level laser, three-level atoms in a cascade configuration are injected into a cavity coupled to a vacuum reservoir via a single-port mirror.…”