Open resonator excited by a wave beam

Open resonators are used in various millimeter, submillimeter and optical wavelength range devices: generators, wavemeters, filters, etc. The theory of resonators is usually formulated in the parabolic equation approximation. According to this theory a set of homogeneous integral equations is derived for fields on mirrors. Eigenfrequencies and quality factors of various modes are found by solving these equations. A research based on this method proves to be effective in the case of a quasiequidistant spectrum of the resonator using one of the indices, e.g., a longitudinal index for a two-mirror resonator. Dielectric bodies of even elementary shape, such as plates several wavelengths thick, placed inside a resonator result in nonequidistancy of its spectrum, the frequencies and losses of modes become dependent on the longitudinal index, i.e. dispersion introduced by the dielectric plate becomes essential. Methods employed to analysis of elementary resonators are inapplicable in this case. In the report the method of research of such systems is offered.