An intuitive technique has been developed in which the lowest- and the higher-order modes for unstable resonators having rectangular or circular mirrors are derived. Instead of two mirrors, it considers the resonator to consist of a train of diffractive edges that are virtual images of the edge of the feedback mirror. Circular-mirror unstable resonators are shown not to exhibit the exact geometrical mode even at high Fresnel numbers.
© 1986 Optical Society of America
Original Manuscript: January 20, 1986
Manuscript Accepted: July 15, 1986
Published: November 1, 1986
W. H. Southwell, "Unstable-resonator-mode derivation using virtual-source theory," J. Opt. Soc. Am. A 3, 1885-1891 (1986)