Non-birefringent cross-slot waveguide

Silicon photonics is a rapidly advancing technology. Silicon based slot-waveguides for high optical mode confinement of quasi-TE (vertical slot) and quasi-TM (horizontal slot) mode have been demonstrated independently. These structures are highly birefringent, which limits their usability in photonic devices. A nonbirefringent structure based on slot waveguide is proposed in this paper. The intensity distribution of the quasi-TE mode in the structure, is simulated with the Film Mode Matching (FMM) method. As expected, the quasi-TM mode has the same effective index as the TE mode and its mode field is confined into the horizontal slot. These structures can be fabricated, etching vertical pattern into a sandwich of grown amorphous Si and horizontal slot layers, then using atomic layer deposition (ALD) method for filling vertical slots and for cladding deposition. Such methods also provide versatility in choosing different materials for horizontal and vertical slots.