Abstract

A numerical analysis of a grating embedded bidirectional optical coupled waveguide structure is presented for the first time, to our knowledge. A finite difference method (FDM) based scheme is devised to extract the allowed eigen TE and TM modes of the structure. Sensing characteristics of the grating employed between two high refractive index couplers are then explored. The influence of strain on the composite structure is numerically analyzed for better understanding of guiding phenomena. A numerical method based on a three-point central finite difference scheme with proper boundary conditions at the point of discontinuity is developed. For an accurate sensitivity analysis, a large number of mesh points ($N = 1000$) are used in the FDM algorithm, while the whole analysis is done on MATLAB software. To the best of the authors’ knowledge, Bragg grating sensitivities of individual TE and TM modes have been estimated for the first time. It is found that higher order TE and TM modes show improved sensitivity performance. The physics behind the improved sensitivity of the proposed structure is correlated with existing cases. The proposed technique is based on effective refractive index theory, and hence it is easy to implement. This work can be easily extended to obtain temperature, humidity, and vibration sensitivities of other novel structures.

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