Coherent spontaneous emission of light (A)

L.O. Schwan

R. Bonifacio, Guiliano Preparata

David C. Gold, Preston Huft, C. Young +4 more

When a quantum system is put into an excited state, it will decay back to the ground state through a process termed spontaneous emission.It is generally assumed that spontaneous emissions between different individual emitters will not be coherent with each other; to produce coherent light, one would need population inversion and stimulated emission.In this work, we show that an optically thin ensemble of 11 000 radiating atoms spontaneously organizes to produce spatially coherent light.The reason for this coherence is collective coupling of the individual emitters via Dicke superradiance and subradiance (as opposed to amplification through stimulated emission).

Iliya V. Doronin, E. S. Andrianov, A. A. Zyablovsky +4 more

Properties of light sources based on amplified spontaneous emission (ASE) are similar to the properties of lasers in many regards. However, even though ASE has been widely studied, its photon statistics have not been settled. There are no reliable theoretical estimates or unambiguous experimental data for the second-order coherence function of photons that characterizes the coherence properties of a light source. Our computer simulation clearly establishes that, independently of pump power, the light produced by ASE is similar to that of a thermal source. This result lays bare the fundamental difference between ASE radiation and laser radiation.

Tong Zhang, Xu Deng, Kai-Kai Zhang +2 more

We propose an efficient scheme to manipulate spontaneous emission spectra using optical vortices carrying orbital angular momentum (OAM) in a coherently driven cold five-level atomic system assisted by a radio frequency (RF) or microwave field. Using experimentally achievable parameters, we find that the spontaneous emission is strongly influenced by quantum destructive interference. And we show that the structured light profile of the probe field can be transferred to the spontaneous emission spectrum via spontaneously generated coherence (SGC). With the aid of SGC, the intensities and detunings of the control and RF fields can be used to tailor the vortex-induced spontaneous emission spectra. When the control and RF fields are configured as vortex beams, it is demonstrated that the spontaneous emission can be coherently controlled through quantum interference by adjusting their topological charges (TCs). Furthermore, we explore intriguing optical properties of the vortex-induced spontaneous emission by varying the TCs of the probe and control fields. This coherently driven atomic system features three closely spaced levels, giving rise to multiple vortex-induced SGC pathways. Our scheme opens avenues for applications in structured light, ranging from optical storage to optical communication.