Prony-method calculation of the mode structure of the HSURIA resonator

The field distributions of various azimuthal and radial modes in the HSURIA resonator without a medium are derived by the Prony method in the 3D diffraction approximation. The HSURIA resonator is capable of single-mode operation. The Prony method makes it possible to find more eigenmodes of the resonator in fewer passes than in the conventional method.