Abstract

The transverse eigenmodes of unstable optical resonators have since their first discovery displayed unusual, even bizarre, eigenvalue and eigenmode properties, into which we are gaining new insights even today, two decades later. Many of these properties arise because the unstable resonator eigenmodes are highly nonpower orthogonal or biorthogonal. As one consequence it becomes possible to inject more energy into an unstable resonator mode that one has in the injecting signal. Unstable resonator modes also experience an excess spontaneous emission or quantum noise at a rate significantly greater than one noise photon per mode. A virtual-source analysis, based on adding up all the edge waves generated inside an unstable system, can help in calculating and understanding the complex mode properties of the unstable resonator.

© 1987 Optical Society of America