An Analysis of Semicircular Channel Backscattering Interferometry Through Ray Tracing Simulations

Niall MC Mulkerns, William H Hoffmann, Ian D Lindsay, Henkjan Gersen

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Recent backscattering interferometry studies utilise a single channel microfluidic system,
typically approximately semicircular in cross-section. Here we present a complete ray tracing model for on-chip backscattering interferometry with a semicircular cross-section, including the dependence upon polarisation and angle of incidence. The full model is validated and utilised to calculate the expected fringe patterns and sensitivities observed under both normal and oblique angles of incidence. Comparison with experimental data from approximately semicircular channels using the parameters stated shows that they cannot be explained using a semicircular geometry. The disagreement does not impact on the validity of the experimental data, but highlights that the optical mechanisms behind the various modalities of backscattering interferometry would benefit from clarification. From the analysis presented here, we conclude that for reasons of ease of analysis, data quality, and sensitivity for a given radius, capillary-based backscattering interferometry affords numerous benefits over on-chip backscattering interferometry.
Original languageEnglish
Article number4301
Number of pages15
Issue number11
Publication statusPublished - 6 Jun 2022

Bibliographical note

Funding Information:
Funding: This research was funded by the EPSRC (grant number EP/L016648/1), the EPSRC/NPIF co-funded by Carbometrics (grant number EP/R51245/X), and an Impact Acceleration Account co-funded by Bristol Nano Dynamics (grant number EP/R511663/1).

Publisher Copyright:
© 2022 by the authors. Licensee MDPI, Basel, Switzerland.


  • backscattering interferometry
  • refractive index
  • semicircular channel
  • ray tracing
  • microfluidics


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