Abstract
The resolving power of metallic linear gratings deposited on a dielectric thin-film waveguide can be increased by separating sections of the grating by blank spaces. Because of the high coupling efficiencies of gratings deposited directly on the waveguide, the effects of the blank spaces cannot be observed for such guides. If a dielectric film with an index of refraction less than that of the guide and with a suitable thickness is used as a spacer to separate the grating from the guide, the properties of sectioned gratings can be observed experimentally. Light from a He–Ne laser was guided in a reactively sputtered 3500-Å-thick Ta2O5 guide separated from an aluminum grating by a sputtered 1200-Å-thick SiO2 layer. The diffraction patterns were measured for continuous and sectioned gratings and compared with theoretical expressions obtained from standard grating theory. These are shown to be satisfactory for the guided-mode case.
© 1974 Optical Society of America
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