Fundamental transverse mode of a 3D ring resonator containing selecting elements

The fundamental mode in ring optical resonators containing selecting elements, as well as field absorbing and amplifying media, is described. In such a case, the elements of the ABCD matrix corresponding to a round-trip over the resonator are complex-valued. The stability conditions for such resonators, which differ qualitatively from those for real-valued matrices, are considered. The concepts of bilateral (bidirectional) and unilateral (unidirectional) stabilities introduced earlier for planar resonators are generalized to 3D resonators, including those with complex astigmatism and noncoplanar optical contours. An example of a resonator with unidirectional stability is considered. (C) 2002 MAIK "Nauka/Interperiodica".