Optical Transducers and Biosensors: Principles and Applications
Classified in Physics
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WEEK4
TRANSDUCER
A transducer is a device that converts an observed change (physical, chemical, or biological) into a measurable signal.
Optical Transducers
Absorption spectroscopy, fluorescence spectroscopy, luminescence, internal reflection, light scattering, surface plasmon resonance, ellipsometry, and fiber optics.
TOTAL INTERNAL REFLECTION and EVANESCENT FIELD
The refractive index n1 is larger for the incident medium than the refractive index n2 of the reflecting medium. Sin(THETA)=n2/n1. However, the electric field of the light penetrates into the second medium and is called the EVANESCENT FIELD. The evanescent field has an extension of several hundred nanometers and can be used as an optical probe if one or more additional layers are present