Probe-Absorption Spectrum of a Polar Quantum Emitter in a Squeezed Finite-Bandwidth Vacuum

A study of the absorption spectrum of a weak-probe beam irradiating a two-level quantum emitter with broken inversion symmetry driven by external monochromatic high-frequency electromagnetic (e.g. laser) field and damped by squeezed vacuum reservoir with finite bandwidth was carried out for the case of the squeezed vacuum source being represented by a non-degenerate parametric oscillator below threshold. It was shown that this atom-driving-field system can either amplify or absorb weak probe electromagnetic radiation beam of much lower frequency than the frequency of the driving field. The shape of the absorption and amplification spectra can be controlled by the degree of the squeezed vacuum source degeneration and by the phase of the squeezing, while the switching between these two modes of operation can only be controlled by the phase of the squeezing.