Optical Waveguide Biosensors

Dual-Mode Electro-Optical Techniques for Biosensing Applications: A Review

“…Silicon photonic biosensors exploit the changes in the propagation constant of optical modes caused by the presence of a surface-immobilized biomolecular layer. A number of highly sensitive optical techniques can be used to monitor this optical shift, for example, interferometry caused by the difference in propagation length or the shift in resonance caused by the change in refractive index due to binding, both leading to a quantifiable signal that is proportional to the amount of biological material present on the sensor surface [ 13 , 17 , 18 , 22 , 23 , 65 ].…”

“…Typically, optical transduction in photonic biosensors is enabled by the sensitivity of an optical surface mode to changes in the local refractive index. By sensitizing the surface to a specific molecule, for example by immobilization of a specific bioreceptor, the local change in refractive index that occurs following a biochemical event, is transduced into the properties of the mode to provide a quantifiable readout [ 16 , 20 , 21 , 22 ] ( Figure 1 ). This phenomenon, called evanescent-wave sensing [ 16 , 20 , 21 , 22 ], is the most common principle exploited for optical sensing [ 15 , 17 , 18 , 23 ].…”

“…By sensitizing the surface to a specific molecule, for example by immobilization of a specific bioreceptor, the local change in refractive index that occurs following a biochemical event, is transduced into the properties of the mode to provide a quantifiable readout [ 16 , 20 , 21 , 22 ] ( Figure 1 ). This phenomenon, called evanescent-wave sensing [ 16 , 20 , 21 , 22 ], is the most common principle exploited for optical sensing [ 15 , 17 , 18 , 23 ]. Depending on the particular optical technique, the changes in the properties of the optical mode can led to a shift in resonance wavelength [ 24 , 25 , 26 ], interference pattern [ 18 , 27 ] or coupling angle [ 15 ].…”

Last Advances in Silicon-Based Optical Biosensors

“…The majority of optical label-free biosensors are based on the evanescent field detection principle: in a waveguide due to total internal reflection at the interfaces, light propagates through the core producing an evanescent wave at the substrate and cladding boundaries [ 9 ] (see Figure 1 ). If a sensing window is etched in the cladding, opening an access to the core surface, the behaviour of the guided light in the core is directly related to any perturbation taking place in the evanescent area over the surface.…”

Engineering functional nanomaterials for biophotonics and nanomedicine applications

“…The optical waveguide is a physical structure that used to guide the electromagnetic wave within the optical spectrum. It can be classified according to the geometry (i.e., strip, planar or optical fiber), the refractive index distribution, and the materials (e.g., metal, glass, semiconductor and polymer) [156,157]. In the optical waveguide based biosensors (Figure 2-1d), the incident light is coupled into the waveguide at the resonance angle, and generates evanescent wave outside the waveguide, resulting in the resonance angle sensitive to the refractive index change of medium near the waveguide [24].…”