Fiber-optic biosensor based on self-mixing interferometry

M. Määttälä, J. Laur, M. Kinnunen, Jukka Hast, R. Myllylä

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

2 Citations (Scopus)


Self-mixing interferometry is a promising technique for a variety of measurement applications. Using a laser diode with an external cavity as interferometer, the technique offers several advantages over traditional interferometric configurations. This research used a self-mixing interferometer built in our own laboratory. It is based on a blue emitting GaN laser diode with a wavelength of 405 nm. Light is directed through an optical fiber from which a 1-cm section of cladding has been removed, and a cuvette for holding the sample is fixed around this part. Interference patterns, created in the laser cavity, are acquired with a computer-based data acquisition system and later processed using Matlab software. Since samples with different refractive indices create interference patterns with different phases, even small changes in sample concentrations can be measured. However, coupling light into a single-mode optical fiber is a very challenging task, and the setup is very sensitive to external interference like airflows or vibrations. Experiments with the device showed that, in stability measurements, the standard deviation of the recorded fringe pattern shifts was only 1.7 nm. In sample measurements, the refractive index change in the sample chamber varied from 1.0029 to 1.33, corresponding to a fringe pattern shift of 297±4 nm.
Original languageEnglish
Title of host publicationSixth International Conference on Advanced Optical Materials and Devices (AOMD-6)
PublisherInternational Society for Optics and Photonics SPIE
Publication statusPublished - 2008
MoE publication typeA4 Article in a conference publication
Event6th International Conference on Advanced Optical Materials and Devices, AOMD-6 -
Duration: 1 Jan 2008 → …

Publication series

SeriesProceedings of SPIE


Conference6th International Conference on Advanced Optical Materials and Devices, AOMD-6
Period1/01/08 → …


  • External cavity
  • Laser diode
  • Optical fiber
  • Refractive index change
  • Self-mixing interferometry

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