Terahertz control of air lasing

Abstract

The coherent emission from ionized nitrogen molecules is of interest for remote sensing and astronomical applications. To initiate the lasing process, we used an intense ultrashort near-infrared (NIR) pulse overlapped with a terahertz (THz) single-cycle pulse. We observed that coherent emission could be seeded and modulated by the amplitude of the THz field, which is the result of a combined effective second-order nonlinear polarization and the nonlinear effects induced by the NIR pump. Our results shed new light on the role of intense transient fields in the coherent emission from photoexcited gas molecules.

A perturbative approach to self-phase modulation and self-steepening of short laser pulses propagating in nonlinear media

“…They are on the order of z R and z R 2 , respectively. Using the above parameters, one finds that the dimensionless scaling parameters identified in (24) are, for = Á 1.2 10 . Since all these parameters (and in particular the sum of the δ and β parameters) are much smaller than 1, the laser pulse can be considered in the perturbative regime.…”

“…The time dependence of the five terms of (21) are illustrated in figure 1 for K=5 with the scaling parameters (24) set equal to 1. The goal here is only to illustrate the functional dependence of the various terms upon τ since the scaling parameters are by definition much smaller than 1.…”

Recent Advances in Air Lasing: A Perspective from Quantum Coherence

“…Molecular nitrogen ion (N) lasing is the third type of air lasing, which originates from the transition from the excited state to the ground state . Lasing actions from N ions have been experimentally observed by several research groups since the first report in 2011 . Besides its promising application in the remote sensing similar to the other two types of air lasing, the understanding of the physical procedure in N lasing is also attracting great interests.…”

“…have generated the N lasing with the energy of 2.6 µJ using TW‐level 800 nm laser pulses, which, to the best of our knowledge, is the highest energy of the air lasing reported so far . Very recently, the N lasing has also been studied with the polarization‐modulated laser field, bicircular two‐color field, and even the synthesized field of near‐infrared and THz pulses . All these experiments have been carried out with the Ti:sapphire laser system as the pump source.…”

Air lasing: Phenomena and mechanisms*

“…[60] By measuring the forward externallyinjected seed-amplification lasing spectra, one could obtain much information such as gain dynamics [61][62][63][64] and remote characterization of rotation coherence, [65] and population densities and dynamics in different rotational levels, [66][67][68][69][70][71] which is significant for understanding the mechanism behind the establishment of the optical gain and achieving the coherent control of the N + 2 lasing. [72][73][74][75] The above mentioned OPA laser has a low laser energy output, making it hard to generate a filament at a remote location, while the pump-probe scheme has a difficulty to temporally and spatially overlap the two pulses over a far distance. A variety of pumping schemes for generation of N + 2 air lasing have been proposed to overcome the above drawbacks.…”