O. Parriaux

Coupling gratings as waveguide functional elements

Waveguide grating couplers allow the essential function of waveguide access to be integrated together with optical processing functions on a monolithic planar substrate. Grating coupling technology is topologically and, to a large extent, technologically compatible with the planar processes which define the optical processing waveguide circuit. Poor coupling efficiency, highly dispersive character, absence of user-friendly modelling tools and fabrication difficulties have long prevented this technology from being implemented into practical sensors and microsystems. This paper makes a review of the points where decisive technological progress has been made, illustrates some useful features of waveguide coupling gratings and underlines some of the difficulties which the designer may encounter.

E-beam tandem writes short-pitch DOEs and gratings for EU-922 FOTA and other optical microsystems

Short grating period and high spatial frequency zones in holograms are features which diffractive elements must exhibit to be considered as the core of future optical microsystems. Wavelength scale feature size is the way to system miniaturization, to large aperture and high efficiency as well as to simplicity. The implication is a systematic resort to electron beam lithography (EBL). A tandem of two EBL tools is shown to fit the specific requirements of diffractive optics and to allow the exploitation of the application potential of this technology.