On-chip refractive index sensor 


Plasmon-based optical sensor concepts typically exhibit optical properties that are highly sensitive to refractive index changes in the vicinity of the sensor surface. As a result, they can, for example, be used as affinity biosensors in combination with surface functionalization. Plasmonic sensors can be based on the excitation and detection of localized particle plasmons (“Localized Surface Plasmon Resonance”, LSPR) in metallic or propagating surface plasmon polaritons (“Surface Plasmon Resonance”, SPR) at extended metal-dielectric interfaces. To date, this type of sensing has not been successfully miniaturized and developed into an on-chip sensor. 


The combination of plasmonic nano-hole grating structures with Ge photodetectors can translate even small refractive index changes directly into photocurrent changes, which can be read out without complex spectrometer-based signal processing and are available for further on-chip processing or wireless data transmission. This enables miniaturized sensor solutions for mobile use or as part of sensor networks. 


High sensitivity with simultaneous miniaturization

On-chip sensor

Refractive index changes can be read out directly as an electrical signal


  • Food and beverage industry
  • Industry 4.0 (process analytics, refractive index measurements in liquids)
  • medical point-of-care diagnostics
  • environmental analytics (detection of bacteria in drinking water)
  • Agriculture 4.0 (chemosensor technology, use as electronic nose)


Implementation of a proof-of-concept device in state-of-the-art silicon technology


Prof. Inga Anita Fischer

Brandenburg University of Technology Cottbus – Senftenberg

Field of expertise: Experimental physics and functional materials

Erich-Weinert-Straße 1
Lehrgebäude 10
03046 Cottbus

M: inga.fischer(at)b-tu.de
T:  +49 (0)355 69 3185