Clinical diagnosis of diseases dependant on genetics of patients is still limited due to the lack of quick, precise, cheap and reliable technological tools. Such diagnostic tools would allow the design of personalized treatments for each patient according to its genetic profile. Photonic biosensors based on evanescent wave detection can afford such diagnostic tools. Using the evanescent wave detection principle, a new bimodal interferometer sensor has been proposed[1]. This device is comprised of a single mode rib waveguide which abruptly increases its core thickness to guide two transversal modes (TX00 and TX10) propagating until the output of the chip. A sensing area is defined in the bimodal part of the waveguide and, as the fundamental and first order modes have different intensity distribution at the core-cladding interface, the interface pattern is a function of the refractive index in the sensing area. A complete study is made starting from the previous device in order to improve its characteristics. The model used for simulations consisted of a variable thickness core layer (260-380 nm) of Si3N4 with n = 2.0 over a 2 µm SiO2 cladding layer with n = 1.46 and water (n=1.33) in the sensing area over the waveguide core using Film Mode Matching (FMM) Method in Photon Design 5.4[2]
