In standard lasers, light amplification requires population inversion between an upper and a
lower state to break the reciprocity between absorption and stimulated emission. However …

Singly ionized nitrogen molecules in ambient air pumped by 800 nm femtosecond laser give
rise to superradiant emission. Here, we study this superradiance by injecting a pair of …

Nitrogen molecular ions (N_2^+) in air plasma pumped by femtosecond laser pulses give
rise to superradiant emission at 391.4 nm in the presence of an external seed pulse at …

Atmospheric lasing has aroused much interest in the past few years. The'air–laser'opens
promising potential for remote chemical sensing of trace gases with high sensitivity and …

Cavity-free lasing of N 2+ induced by a femtosecond laser pulse at 800 nm is nearly totally
suppressed by a delayed twin control pulse. We explain this surprising effect within the V …

We report on a pump-probe investigation of vibrational Raman scattering from coherently
excited N 2+ ions. It is found that the Raman signals produced by the inelastic scattering of …

We investigate free-space lasing actions from molecular nitrogen ions (N 2+) at the
wavelengths of~ 391 nm and~ 428 nm. Our results show that pronounced gain can be …

摘要空气激光是以空气为增益介质产生的相干辐射, 具有高准直度, 高相干性,
高**度以及自由空间传输等优点, 为远程探测提供了全新的技术途径. 同时, 空气激光是**场超快 …

We develop a mathematically simple yet accurate model for the single-pulse non-resonant
impulsive alignment of thermal ensembles of linear molecules. We find that our molecular …

A near-infrared laser pulse generates lasing of N 2+ during filamentation, while the
underlying mechanism of optical gain is still under debate. Here, we study the rotational …