Mode analysis of an open-boundary cerenkov laser in the collective regime

The mode analysis of an open-boundary Cerenkov laser is developed in the collective regime. The Cerenkov laser under consideration consists of a relativistic slab electron beam and a dielectric-loaded conducting plane. The beam and the dielectric are assumed to be arbitrary in thickness, with an arbitrary gap allowed between them. For the Cerenkov laser specified above, the dependence of the growth rate upon the electron density of the beam, the beam-dielectric gap, the beam thickness, and the drift velocity of the beam is clarified. In particular, the following results deserve special attention. First, with other parameters kept invariant, the growth rate approaches a constant value for the beam thickness greater than the reactive skin depth of the beam. Second, the growth rate becomes maximum at the drift velocity of the beam characteristic of a particular electromagnetic wave mode with which the space charge wave interacts. As the mode number increases, the characteristic drift velocity shifts to higher values whereas the value of the maximum growth rate decreases.