Narrowband Biphoton Generation due to Long-Lived Coherent Population Oscillations

TL;DR

This paper investigates narrowband biphoton generation through long-lived coherent population oscillations in a pumped two-level system with a metastable state, resulting in controllable, long-coherence biphotons with antibunching properties.

Contribution

It introduces a method to generate narrowband biphotons using long-lived population oscillations, enhancing control over photon properties in quantum optics.

Findings

Biphotons have narrow bandwidth and long coherence time.

The biphoton antibunching period is set by the dephasing time.

Damped oscillations occur in the biphoton wavefunction with non-zero pump detuning.

Abstract

We study the generation of paired photons due to the effect of four-wave mixing in an ensemble of pumped two-level systems that decay via an intermediate metastable state. The slow population relaxation of the metastable state to the ground state is utilized to create long-lived coherent population oscillation, leading to narrowband nonlinear response of the medium. The biphotons have a narrow bandwidth, long coherence time and length, which can be controlled by the pump field. In addition, the biphotons are antibunched, with antibunching period determined by the dephasing time. During this period, damped oscillations of the biphoton wavefunction occurs if the pump detuning is non-zero.