Optical Tamm mode based refractometer in all-dielectric configuration

•Analytic analysis for photonic bandgap-guided surface modes known optical Tamm modes using Bloch-wave theorem.•Use the dispersion relations to identify its potential for devising a refractometer.•Refractometer sensitivity tailoring t for both the transverse-magnetic as well as transverse-electric optical Tamm modes.•Comparisons with plasmonic and interferometer-based refractometer: advantages and disadvantages.

Optical Tamm (OT) modes formed at the interface of distributed-Bragg reflector (DBR) and low-index dielectric material, exhibit strong dispersive features at optical frequencies which gives rise to the possibility of designing refractometer with improved sensitivity. Using this idea, we design a TiO2/SiO2 based DBR configuration for sensing refractive-index changes around 1.33 using spectral-interrogation as well as angular-interrogation method. Dispersion characteristics of OT modes in the DBR configuration are tailored to obtain spectral sensitivity ∼1200 nm/RIU and angular sensitivity ∼40°/RIU for both transverse-electric (TE) and transverse-magnetic (TM) polarizations. We also show that the sensitivity could be substantially tuned over a wide range by appropriately choosing the thicknesses of DBR constituent layer. An all-dielectric DBR configuration gives rise to the possibility of realizing refractometer in any desired spectral region by linearly translating the dispersive behavior of photonic bandgap (PBG) guided OT modes.