Optical sensing by optimized silicon slot waveguides

Abstract

A theoretical investigation of silicon-on-insulator nanometer slot waveguides for highly sensitive and compact chemical and biochemical integrated optical sensing is proposed. Slot guiding structures enabling high optical confinement in a low-index very small region are demonstrated to be very sensitive to either cover medium refractive index change or deposited receptor layer thickness increase. Modal and confinement properties of slot waveguides have been investigated, considering also the influence of fabrication tolerances. Waveguide sensitivity has been calculated and compared with that exhibited by other silicon nanometer guiding structures, such as rib or wire waveguides, or with experimental values in literature.

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

“…Although, generally SOI structures with H = 220 is more widely used, however, as it is shown here that higher heights yield better sensors, so optimized slot height for our device is taken as 500 , which would be easy to fabricate [21], yields Γ − = 41.965% and = 0.0104. So far we have kept the slot width (W s ) fixed at 100 , as it was theoretically optimized for slot waveguide based homogeneous sensor [22] and also successfully used in labelfree slot based ring resonator for bio sensing application [5]. However, the slot width (W s ) variation with optimized W (190 ) and H (500 ) shows the maximum Γ − = 42.405% at a slightly wider slot width, W s = 130 , shown by a red dashed-dotted line in Fig.…”

High-Sensitivity Polarization-Independent Biochemical Sensor Based on Silicon-on-Insulator Cross-Slot Waveguide

“…Effective index, n eff of the guided mode in a WG is affected by the change of molecular adlayer (which can be called sensing layer) thickness caused by the interaction between analyte and receptor molecules. The WG sensitivity, S, can be defined as [3]:…”

“…The change in n eff , , produced by the change of the sensing layer thickness, , can be related approximately by the light confined in sensing layer and there is a positive correlation between the and confinement factor in the sensing layer for the guided modes in a slot WG [3], which can be defined as: (2) where E is the electric field, H is the magnetic field, * denotes a complex conjugate, R e returns the real part of a complex number, and S indicates sensing layer.…”

“…effective index is affected either by the change of the refractive index of the cladding medium, known as homogeneous sensing, or the change in the thickness of an ultra-thin layer of receptor molecules which are immobilized on WG surface, known as surface sensing [3]. Based on that, various kinds of integrated optical structures have been proposed to measure the change in the effective index, such as those based on directional couplers [4], Mach-Zehnder interferometers [5], and micro ring resonators [6].…”

Computational Study of Photonic Crystals Nano-Ring Resonator for Biochemical Sensing

“…The first scheme is the detection of effective refractive index change in terms of homogeneous sensing, i.e., influenced by refractive index modification of covered medium. The second scheme is surface sensing, i.e., interfered by thickness change of thin biomolecular layer immobilized on surface [3], [4]. The label-free affinity-based optical biosensors allow us to study the selective binding between target molecules and captured agents without using a fluorescence or radio label.…”