High-Gain, High-Order Vortex Air Lasing Generated by Plasma Amplification

Vortex air lasing opens exciting perspectives for remote generation, amplification, and control of vortex beams in ambient air. By combining the advantages of air lasing and vortex beams, it holds great potential in some specific applications such as standoff detection of chiral molecules and rotating objects. However, it remains challenging to produce high-order vortex air lasing and flexibly control its orbital angular momentum, hindered by the inhomogeneous distribution and instability of laser-induced plasma. Herein, vortex (Formula presented.) lasing with a tunable vortex order from the first up to the tenth order is achieved through vortex seed amplification in plasma. The helical phase structure of the seed is well conserved in the amplification process. Each order vortex air lasing shows the same topological charge as the seed and a doughnut-shaped profile. Moreover, the amplification factor is up to 10⁴. Generation of high-order, high-gain vortex air lasing is attributed to the choice of an appropriate population-inversion system, as well as the optimal control over spatial matching of pump and seed beams, gas pressures, and focusing conditions. This work facilitates the understanding of the gain mechanism of (Formula presented.) lasing and promises to extend the application scenarios of air-lasing-based spectroscopy.