THE RADIATION FIELD EIGENMODES IN GAIN MEDIA—THE 3-D SOLUTIONS OF FREE ELECTRON LASERS AND OPTICAL GUIDING

A set of eigenmodes of radiation field is obtained in the media with quadratic equivalent index of refraction. Taking the set of eigenmodes as expansion basis, the fully 3-D problems relative to free electron lasers can be solved in the frame of perturbation approach. The optical guiding of FELs by the off-axis displacement of the eletron beam is treated as an example of 3D-FEL problems.