OPTICAL DEVICE INCLUDING A BURIED GRATING WITH AIR FILLED VOIDS AND METHOD FOR REALISING IT

摘要

The present invention is relative to an optical device (100) including a waveguide (4) and to a method for the realisation of a waveguide on a substrate (3). Said waveguide comprises a core (2) surrounded by a cladding (1), said cladding including a lower cladding (5), the core being placed above the lower cladding, a lateral cladding (7) adjacent to a first and a second opposite lateral sides (13,14) of the core, and an over-cladding (6), said over-cladding being positioned above said core and lateral cladding. The core and lateral cladding define a guiding layer. A grating structure (99) is formed in said guiding layer, which comprises a plurality (8, 9) of empty trenches (11). The over­-cladding comprises a cap layer (6a), said cap layer has a first refractive index and is in contact with the grating structure and the first refractive index of said cap layer is substantially identical to the refractive index of the lateral cladding in contact with said cap layer. Additionally the cap layer is located above said trenches and forms bridges connecting each couple of adjacent trenches of said plurality, so that voids are formed in the trenches.