Estimation of cover sensitivity of a planar polymer waveguide through double path broadband difference interferometeric analysis

Abstract

Broadband difference interferometeric analysis of a double path planar polymer optical waveguide is presented for bio-sensing applications. Mathematical formulation of intensity of output signal is obtained using interferometeric analysis. Further, the dispersion equation is obtained by matching the field at core cladding interface that gives the cutoff film thickness for TE0 and TM0 modes in considered spectral range. The waveguide is analyzed by propagating either same polarized (TE[sbnd]TE or TM[sbnd]TM) modes or unlike polarized (TE[sbnd]TM) modes in the reference arm and sensing arm. It is observed that difference of propagation constant for same polarized mode increases with increase of wavelength while for unlike polarized modes it first increases up to a maximum value and then decreases in the considered wavelength range. The maxima of output interference signal shifted prominently with the cover refractive index for the wavelength range near the maximum value of propagation constant difference. The obtained sensitivity 9.226 for unlike polarized modes in arms is much larger than the sensitivity 0.071 of same polarized modes in arms. © 2020 Elsevier GmbH