The forked blazed grating as a quasioptical element for gyrotron applications

In previous papers we have shown how beams of millimeter-wavelength electro magnetic radiation with phase singularities can be generated by diffraction from a specially-configured forked blazed grating. Here we consider how th e hollow coni cal beam output of a gyrotron is diffracted by this kind of g rating. Two applications are considered; using the grating (a) as a single- element quasioptical antenna to convert the output into a well-collimated g aussian-like beam and (b) as a device to enable the estimation of the fract ions in oppositely-rotating modes in the gyrotron output.