Photon accelerator

Abstract

A novel method of frequency upshifting short (\ensuremath{\le}1 ps) pulses of laser light, which makes use of relativistic plasma waves, is described. This method makes use of the fact that a laser pulse moving in a plasma can be thought of as a packet of photons, each possessing an effective mass of ${m}_{\ensuremath{\gamma}}$=\ensuremath{\Elzxh}${\ensuremath{\omega}}_{\mathrm{pe}}$/${c}^{2}$ and moving with the group velocity of the laser pulse. These photons experience a force acting on them when in the presence of a gradient in the plasma density. By using a relativistic plasma wave (i.e., a moving density gradient) traveling with the photons, energy of the photons (thus the frequency) can be continuously increased.