Reflective arrayed waveguide grating multiplexer

Abstract-High-performance reflective arrayed waveguide grating multiplexer/demultiplexer designed for compatibility with silicon integrated circuit processing is described. The grating, folded by a flat reflecting surface, can be printed in a single-exposure field of a photolithographic stepper. Advanced plasma assisted deposition is used to prepare waveguides with very low loss and minimum birefringence. Multiplexers with 40 channels separated by 100 GHz show intrinsic insertion losses of -2.4 dB, channel uniformity less than 0.6 dB, and very low polarization dependent wavelength shift of 0.012 nm. Index Terms-Optical planar waveguide components, phased arrays, silica waveguides, waveguide arrays, wavelength division multiplexing. I N THE USUAL design of arrayed waveguide grating (AWG) devices the grating is placed between the input and output star couplers [1]- The desire for a compact grating has been a constant theme in the development of AWGs, discussed in a number of reviews [6]-[8]. It is driven by the possibility of cost reduction associated with reduced size, lower optical losses, and lower sensitivity to material nonuniformities. Dragone The constant length difference value of 12.3 m between grating waveguides used in our folded design is half of the value of the similar unfolded one. This corresponds to a diffraction order of . The small value of makes it possible to place up to 333 waveguides in the grating, with the separation of 25.6 m between waveguides at the output arc of the slab waveguide. Another design consideration is to have waveguides equidistant at the reflecting surface. This allows for a simple planar reflecting surface, easy to fabricate by cutting and polishing. With these design requirements, and a conservative minimum radius of curvature of 12 mm, gratings with an area of cm could be constructed. The separation between waveguides of the input/output coupler, at the input arc of the slab waveguide, was 25.0 m. With 4