Sensitivity optimization of an evanescent field particle detector based on a silicon nitride waveguide

Anton Buchberger*, Paul Maierhofer, Jochen Kraft, Marcus Baumgart, Alexander Bergmann

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference paperpeer-review


Optical sensors that utilize the evanescent field of an integrated waveguide are applied in a wide range of applications. Recently, evanescent field particle detectors based on dielectric strip waveguides were success- fully used for the detection of small particles (0 < 1 μm). We present optimizations of silicon nitride slab and strip waveguides based on numerical simulations, which maximize the evanescent field that interacts with the analyte such as particles. The fraction of the total light power that is transmitted in the evanes- cent region can be tuned by geometric parameters of the waveguide and the operation wavelength. We show that the optimum height of the slab waveguide scales linearly with the operation wavelength, which is in agreement with analytic results from literature. Moreover, linear correlations between the optimum waveguide geometry and wavelength could be derived for silicon nitride strip waveguides that are utilized for particle detection. The results for the optimum strip waveguide geometry are dependent on the target particle size. The derived geometries represent the optimum configuration for an evanescent field particle detector based on silicon nitride strip waveguides in order to exploit its full potential in terms of detection sensitivity. Enhanced sensitivities will be necessary to extend the detection range of evanescent field particle detectors down to small particles in the ultrafine regime (o≤ 100 nm).

Original languageEnglish
Title of host publicationNanoengineering
Subtitle of host publicationFabrication, Properties, Optics, Thin Films, and Devices XVII
EditorsBalaji Panchapakesan, Andre-Jean Attias, Wounjhang Park
ISBN (Electronic)9781510637405
Publication statusPublished - 1 Jan 2020
Event2020 Nanoengineering: Fabrication, Properties, Optics, Thin Films, and Devices - Virtuell, United States
Duration: 24 Aug 20204 Sept 2020
Conference number: XVII

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


Conference2020 Nanoengineering: Fabrication, Properties, Optics, Thin Films, and Devices
Country/TerritoryUnited States


  • evanescent field
  • integrated particle detector
  • integrated waveguide
  • sensitivity enhancement
  • silicon nitride photonics
  • single particle counting
  • ultrafine particles

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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