An Innovative Straight Resonator Incorporating a Vertical Slot as an Efficient Bio-Chemical Sensor

Abstract

A compact and integrated label-free refractometric bio-chemical sensor based on silicon-on-insulator (SOI) is proposed and comprehensively studied at the telecommunication wavelength of $\lambda = {\text{1550}}\;{\text{nm}}$ . This device incorporated a three-dimensional (3D) Fabry–Perot cavity in the nano-scale regime with maximum footprint area around ${\text{470}} \times {\text{473}}\;{\text{nm}}^{\boldsymbol{2}}$ . A resonance shift ( $\Delta {\lambda _{{\rm{res}}}}$ ) of $\text{5.2}\;{\text{nm}}$ is reported for an ultrathin ( ${\text{5}}\;{\text{nm}}$ ) bio-layer sensing. Besides, an improved maximum sensitivity (S $ = {\text{820}}\;{\text{nm/RIU}}$ ) is also achieved for bulk refractive index change in surroundings. As a chemical sensor, very low detection limit ( $\text{DL} = {\text{6.1}} \times {\text{10}}^{-\text{6}}\;{\text{RIU}}$ ) also can be possible to achieve by this device. All the numerical investigations and optimizations were carried out in frequency domain by a numerically efficient and rigorous full vectorial H-field based 2-D and 3-D finite element methods (FEM). A 3D-FEM code is developed and used to find out the wavelength dependencies of the resonator. Possibility of easy CMOS fabrication and integration opportunities make this structure as a prospective and efficient lab-on-chip device.