A novel configuration of photonic sensors based on a single-channel bimodal interferometer is proposed. The design consists of a subwavelength grating (SWG) periodic structure supporting two dispersive TE-like modes that interfere at the output to create fringes in the transmission spectrum. Dispersion relations of the bimodal periodic structures have been computed in order to study the sensing performance, obtaining a theoretical bulk sensitivity of ~1300nm/RIU and a surface sensitivity of ~6.1nm/nm. Finite-Difference Time Domain (FDTD) analysis has been also carried out in order to confirm the previously obtained sensitivity results, thus showing a perfect agreement between theoretical modelling and simulation.