Photon acceleration based on plasma.
A formalism is presented to examine the interaction of laser field with plasma wave in which the interaction is described as some geometric metric (optical metric) and then a laser beam is treated as a packet of photons moving along null geodesics with respect to that metric. Photon motion equations are derived and solved analytically in both the one-dimensional and the three-dimensional cases. The expressions for the frequency shifts of laser pulses are presented and it is found that the frequency shifting results from the plasma density gradient. Three-dimensional solution shows that a laser beam diffraction occurs in the presence of a radial variation of the plasma density. It is argued that the focusing mechanism originated from the plasma wave can curb laser diffracting, so that photons can be trapped in the plasma wave and accelerated continuously.
Ji
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Department of Physics, Shanghai University, Shanghai, 200436, People's Republic of China.