Design and analysis of transmission enhanced multi-segment grating in MZI configuration for slow light applications

This paper proposes to use slow light effects near the Brillouin zone band edge of one-dimensional gratings for reducing the size of integrated electro-optic (EO) modulators. The gratings are built within the arms of a Mach-Zehnder Interferometer (MZI) for intensity modulation. To overcome the inherent high reflection and low extinction ratio, we introduce various multi-segment grating designs. We use coupled-mode theory and derive transfer matrices to analyze the spectral transmittance and phase delay of each arm of the interferometer. Calculations show that a size-reduction of a factor of 2 or more can be achieved at λ=1.574 µm with an insertion loss of 0.17 dB and an amplitude modulation extinction ratio of 18.84dB. The simulated structure is based on a Si slab-waveguide 0.2 μm thick with 30 nm deep grating groves on SiO(2)> substrate.