Abstract
A guided-wave chemical sensor for the detection of environmental pollutants or biochemical substances has been designed. The sensor is based on an asymmetric directional coupler employing slot optical waveguides. The use of a nanometer guiding structure where optical mode is confined in a low-index region permits a very compact sensor (device area about 1200 μm2) to be realized, having the minimum detectable refractive index change as low as 10-5. Silicon-on-Insulator technology has been assumed in sensor design and a very accurate modelling procedure based on Finite Element Method and Coupled Mode Theory has been pointed out. Sensor design and optimization have allowed a very good trade-off between device length and sensitivity. Expected device sensitivity to glucose concentration change in an aqueous solution is of the order of 0.1 g/L.
Highlights
In recent years considerable research effort has been developed to employ electronic and optical micro- and nano-sensors in a great number of application fields such as medicine, microbiology, particle physics, automotive, environmental safety and defence
Different kinds of integrated optical chemical sensors have been proposed over the years, like those based on directional couplers [2], Mach-Zehnder interferometers [3,4,5], Bragg gratings [6,7], micro-ring resonators [8,9,10], and photonic crystal micro-cavities [11]
We propose the use of slot waveguides to design an asymmetric directional coupler for optical chemical sensing
Summary
In recent years considerable research effort has been developed to employ electronic and optical micro- and nano-sensors in a great number of application fields such as medicine, microbiology, particle physics, automotive, environmental safety and defence. Different kinds of integrated optical chemical sensors have been proposed over the years, like those based on directional couplers [2], Mach-Zehnder interferometers [3,4,5], Bragg gratings [6,7], micro-ring resonators [8,9,10], and photonic crystal micro-cavities [11] Many of these devices have been realized adopting CMOScompatible technological processes. By monitoring the slot guiding structure effective index in an appropriate integrated architecture (e.g. Mach-Zehnder interferometer, ring resonator, Bragg grating, directional coupler, and so on), it is possible to fabricate highly sensitive and miniaturized integrated optical chemical sensors. Model validation by an accurate simulation tool based on 3D EigenMode Expansion (EME) method [55] has been performed
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