ABSTRACT
This chapter outlines some of the techniques which have been applied to determine the resonator modes of a variety of cavity configurations. It introduces the scalar diffraction type calculations pioneered by Fox and Li in 1960 and the development of more sophisticated procedures and applications thereafter. In 1960, A G Fox and T Li at Bell Telephone Laboratories published the results of their pioneering theoretical investigation to determine the lowest order transverse modes in Fabry–Perot interferometers, which constitute the basic resonators in laser oscillators. Information about the higher order modes is essential to determine the resonator transverse mode discrimination, and to avoid configurations which result in mode degeneracy or mode beating. To obtain solutions for the higher order modes of the Fabry-Perot resonator, Fox and Li modified their earlier algorithm to compute the optical resonator modes by the method of resonance excitation.
