Pulsed cooperative backward emissions from non-degenerate atomic transitions in sodium

Abstract

We study backward cooperative emissions from a dense sodium atomic vapor. Ultrashort pulses produced from a conventional amplified femtosecond laser system with an optical parametric amplifier are used to excite sodium atoms resonantly on the two-photon 3S 1 2 -4S 1 2 transition. Backward superfluorescent emissions (BSFEs), both on the 4S 1 2 -3P 3 2 and 4S 1 2 -3P 1 2 transitions, are observed. The picosecond temporal characteristics of the BSFE are observed using an ultrafast streak camera. The power laws for the dependencies of the average time delay and the intensity of the BSFEs on input power are analyzed in the sense of cooperative emission from nonidentical atomic species. As a result, an absolute (rather than relative) time delay and its fluctuations (free of any possible external noise) are determined experimentally. The possibility of a backward swept-gain superfluorescence as an artificial laser guide star in the sodium layer in the mesosphere is also discussed.

Continuous-wave mirrorless lasing at 221 μm in sodium vapors

“…Despite the significant progress in recent years, there is a demand for stronger return that is needed for faster and more accurate image correction. Our approach using cw resonant excitation may turn out to be more practical compared with recently obtained backward cooperative emission from dense Na vapors using ultrashort pulses produced by an amplified femtosecond laser [19]. Fig.…”

“…Investigations of nonlinear mixing and directional light generation using cw lasers have been carried out almost exclusively using Rb atoms. Here, motivated by possible applications in remote detection [15][16][17] and, particularly, by the possibility of generating backward-directed emission from the mesospheric sodium layer [18,19], we report on the experimental observation of the cw mirrorless lasing on the 4P3/2-4S1/2 transition in Na vapors (Fig. 1) and the study of its spectral and spatial characteristics.…”

Recent Advances in Air Lasing: A Perspective from Quantum Coherence

“…Besides great achievements of the air lasing in the literature, there are still many open questions and opportunities remaining for further explorations. Many efforts have been applied toward understanding the underlying physics from these complex systems and also pushing forward the realization of the air lasing in the atmosphere outside of the laboratory . It has also been proposed to utilize the effect of beam filamentation in open‐air to enhance the described lasing mechanisms .…”

Ultrafast dephasing in hydrogen-bonded pyridine-water mixtures

“…The decay (i.e., emission) occurs on a time scale much shorter than spontaneous decay from the independent individual atoms (or molecules). The picosecond collective emissions from alkali atomic ensemble excited by femtosecond laser pulses have been extensively studied in series of experiments [35][36][37][38][39][40][41] . The present system of pairs of molecules is simplified into three-level system considering only triangular ring mode.…”