Effect of stress and groove geometry on the performance of an IBG filter with Si3N4-filled corrugations

Abstract

We design and estimate the performance of an integrated Bragg grating (IBG) filter that has Si3N4-filled periodic grooves on a silicon strip waveguide. Also, the entire IBG filter is covered with Si3N4 cladding. The refractive index variation along the length of the filter is achieved by the periodic Si3N4-filled corrugations. We consider different geometries of grooves that can be other than the ideal rectangular shape as a result of fabrication limitations. Moreover, we also include the stress-optic effect, which arises because of the different thermal expansion coefficients and lattice constants of the core and cladding materials, to estimate filter performance. We categorically estimate the impact of groove geometry and the stress-optic effect on the filter performance—namely, resonance wavelength, bandwidth, extinction ratio, and side-lobe suppression ratio. Also, the effects of varying the waveguide width, cladding thickness, and corrugation depth on the optical performance of the proposed filter is studied. Our numerical studies reveal that a larger magnitude of stress can be found for lower waveguide width, lower cladding thickness, lower corrugation depth, and rectangular corrugation shape. The estimated changes in the resonance wavelength, bandwidth, extinction ratio, and side-lobe suppression ratio due to the stress effect and geometrical variation of the groove for the IBG filter designed with a waveguide width of 300 nm (600 nm), cladding thickness of 100 nm (400 nm), and rectangular corrugation depth of 10 nm (50 nm) are 1891 pm (1593 pm), 21% (3.8%), 27.2% (5.5%), and 26.9% (5.4%), respectively. The significant performance variation in the IBG filter due to stress and groove shapes emphasizes the need to address these factors to estimate the performance of the proposed IBG filter.