Nanophotonic ring resonator for biosensing applications

Introduction Surface plasmon resonance (SPR) sensors, which use surface plasmon polariton (SPP) waves to probe interactions between biomolecules and sensor surfaces, have attracted tremendous interest in the past decade for optical detection of small biological or chemical entities in liquids [1]. Recently we have proposed a highly sensitive SP interference sensor based on silicon-on-insulator technology. The basic element of the sensor is a surface plasmon interferometer consisting of a thin layer of gold embedded in a silicon membrane. It was demonstrated that the device could achieve a sensitivity of 463.5 nm/ RIU (refractive index unit) and a resolution of 1x10 RIU with regards to wavelength interrogation [2]. Besides SP interference sensors, highly sensitive and integrated label-free biosensors based on ring resonators on silicon-on-insulator platform have been demonstrated [3]. However, all of those integrated sensors were made in dielectric materials and typical dimensions of waveguides and optical components were too large to be miniaturized leading to not well-suitable for lab-on-chip applications. In this contribution, we propose novel nanoscale sensing structures based on plasmonic ring resonators (PRR). It results in very compact sensors in terms of high integration in dimension of a few hundred nanometers associated with a high sensitivity.