These devices can function as amplitude modulators in an integrated circuit by placing an electro-optic material in one half. A dip in coincidence counts in one of these devices appears in the Hong–Ou–Mandel effect, which may be used to implement an experiment that uses one of these devices named for Mach and Zehnder. (15[1])That “delayed choice” experiment proposed by Wheeler uses these devices to investigate “which-way” information from the double slit experiment. Fibre-optic gyroscopes are an example of the (*) ring conformation of these devices, in which they exhibit the Sagnac effect. A double-path one of these devices was used to investigate the luminiferous aether by Michelson and Morley. For 10 points, name these devices that use a beam splitter to superimpose two rays of light and produce a namesake constructive or destructive phenomenon. ■END■