Phase-dependent propagation in a two-level system with intermediate states

Abstract

We study the phase-dependent propagation of a strong, resonant pump and two weak symmetrically detuned fields in a two-level system with population decay through a cascade of intermediate levels.As this system forms a closed loop, the propagation is phase-dependent. For an initial total phase = 0, there is constructive interference between the two weak fields, leading to parametric amplification on propagation. When = π , destructive interference occurs, leading to absorption of the weak fields on propagation. When the weak fields are initially equal in intensity, and = 0, π, remains constant on propagation. For other initial phases, changes on propagation. Dramatic phase changes from π to 0 can occur when the weak fields are initially unequal in intensity and = π .

From fast to slow light in a resonantly driven absorbing medium

“…In fact, a more direct analysis is provided by the basic model of saturable absorber [33] and, as shown in detail in [36], the signals observed in most CPO experiments can be perfectly reproduced by means of Eqs. ( 18) and (19), eventually extended to take into account inhomogeneous effects.…”

“…The pulse may thus be seen as a continuous superposition of fields symmetrically detuned from the cw field (sidebands) that probe the changes of the TLS properties induced by the cw. The propagation in a strongly driven TLS of two symmetrically detuned fields is a basic problem in nonlinear optics [18,19]. When the sidebands are associated with an amplitude modulation, it has been experimentally evidenced [20] and theoretically demonstrated [18,21] that the transmission of the modulation presents a maximum on resonance for strong enough cw intensities.…”

Multiphoton coherent population oscillation

“…In the case of the "classical" CPO, for which γ 2 ≈ γ o ≫ γ m , we have κ ≫ κ T LS , so that in the denominator of Eq. ( 55) we can omit κ T LS and obtain the same result as in [12] W = γ m (1 + κ) .…”

Narrowband-biphoton generation due to long-lived coherent population oscillations

“…This leads to a narrow dip in the probe absorption spectrum and a narrow peak in the FWM spectrum [13][14][15]. Under these conditions and taking into account that level |c is the metastable level γ ca ≪ γ ba , γ bc the steadystate response of the medium to the generated fields is given by [15,16]…”

“…where V 0 = d ba E 0 / (2 ) is the pump Rabi frequency which is assumed to be real, long-lived CPOs of ground and metastable states are created [13]. This leads to a narrow dip in the probe absorption spectrum and a narrow peak in the FWM spectrum [13][14][15]. Under these conditions and taking into account that level |c is the metastable level γ ca ≪ γ ba , γ bc the steadystate response of the medium to the generated fields is given by [15,16]…”