(19) United States
(12) Patent Application Publication (io) Pub. No.: US 2003/0197862 Al
Cohen et al. (43) Pub. Date: Oct. 23,2003
(51) Int. CI.7 G01J 3/40; G01J 3/28
(52) U.S. CI 356/328; 356/305
A planar spectrograph for demultiplexing optical wavelength signals includes a monolithic substrate. The substrate has a diffraction grating etched therein. The diffraction grating is integrally formed in the subtstrate to be in operative relationship with input light to diffract and reflect the input light to a detector. A recess is formed in the substrate to accommodate a separate slab waveguide. A slab waveguide is dimensioned and configured to fit within the recess, and the waveguide guides input light to and from the diffraction grating. A silicon-on insulator spectrographs is also described, as well as, fabrication processes for manufacturing these spectrographs.