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Modeling of coupled-resonator optical waveguide (CROW) based refractive index sensors using pixelized spatial
1Photonic Device Laboratory, Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong SAR, China.
Abstract:
We model and analyze coupled-resonator optical waveguide (CROW) based refractive index (RI) sensors using pixelized spatial detection. Our modeled cascaded Fabry-Perot (FP) CROWs reveal that the intra-band states mode-field distributions vary upon effective RI change at a single wavelength. The spatial Fourier transform of the CROW mode-field distributions, with each cavity field intensity integrated as a pixel, shows spatial frequency peak shift, which constitutes the basis of such a spatial domain sensor. The spatial domain sensing performance depends on the cavity number, the cavity length and the inter-cavity coupling. Our modeled 21-element CROW sensor attains a detection limit of 10(-4) refractive index unit (RIU) with a sensing dynamic range of 10(-3) RIU. Detailed analysis of the spatial frequency harmonic peak amplitude variation further suggests an improved detection limit. Finite-difference time-domain (FDTD) simulations of an 11-element microring CROW device shows sensitivity consistent with the FP modeling.
