A preliminary study on air-borne lightwave amplification using Weibel-type instabilities
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Within man-made plasma sources, including the fusion experimental machines such as the Tokamaks, a phenomenon called the “Weibel EM instability” emerges at times. In all cases, such plasma instability constitutes a valid path for system energy loss, and thus is undesirable. Here, instead, a possibility is explored in which such instability is attempted for good use, viz, amplifying lightwaves in open space of arbitrary wavelengths and amplitudes. Obviously, this is to be compared with the traditional means via spatially-confined, wavelength-restricted erbium-doped optic fibers. The adopted approach here was to utilize artificial plasma in the controlled form of vertically oscillating (with respect to the intended incident light) electrons on a conductive grating. That is, free energy of the sloshing electrons was used to trigger Weibel type instability to act on the incident lightwave in the hope that exponential growth of the latter would occur. It turned out that the anticipated lighwave amplification in air was evidenced unambiguously by experiments with the aid of a lock-in amplifier. The desirable amplitude enhancement could have been one to two orders of magnitude, in principle, had the phasing, amplifier transparency been properly conditioned and arranged for the incident waves. However, to achieve these ambitious goals in the future, nontrivial tasks, especially phase synchronization among the plasma electrons and photons of different coherent wave packets, need to be accomplished in the first place.