confocal resonator

confocal resonator

[kän′fō·kəl ′rez·ən‚ād·ər]
(electromagnetism)
A wavemeter for millimeter wavelengths, consisting of two spherical mirrors facing each other; changing the spacing between the mirrors affects propagation of electromagnetic energy between them, permitting direct measurement of free-space wavelength.
(optics)
A beam resonator that consists of a pair of spherical mirrors which have the same axis of rotational symmetry and are positioned so that their focal points coincide on this axis.