Figure 7.

Graphene plasmonic-based source for short wavelength radiation. (a) shows the electrons-plasmon interaction, where the white dotted line demonstrates the free electrons interacting with plasmons glowing with blue and red bars, (b) illustrates the process of graphene plasmons emission from hot carriers. (c) The soft and hard X-ray radiation from graphene-based free electrons radiation source was achieved without any acceleration stage, with various frequency conversion region, the lines correspond to confinement factor (n = 1,50… 1,000) where n = 1 is shown as a reference. (d) shows the up-converting (black line) and down convection (dash line) of related frequency from graphene-based free electrons source. It is observed that the coupling of phase velocity of graphene plasmons velocity and electrons velocity cause the down-conversion of frequency [116].