• Photonics Research
  • Vol. 12, Issue 8, 1673 (2024)
1,2 and 2,*
Author Affiliations
  • 1SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, UK
  • 2Humboldt Centre for Nano and Biophotonics, Department of Chemistry, University of Cologne, Cologne, Germany
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    DOI: 10.1364/PRJ.522018 Cite this Article Set citation alerts
    Ross C. Cowie, Marcel Schubert, "Light sheet microscope scanning of biointegrated microlasers for localized refractive index sensing," Photonics Res. 12, 1673 (2024) Copy Citation Text show less

    Abstract

    Whispering gallery mode (WGM) microlasers are highly sensitive to localized refractive index changes allowing to link their emission spectrum to various chemical, mechanical, or physical stimuli. Microlasers recently found applications in biological studies within single cells, in three-dimensional samples such as multicellular spheroids, or in vivo. However, detailed studies of biological samples also need to account for the structural heterogeneity of tissues and live animals, therefore requiring a combination of high-resolution microscopy and laser spectroscopy. Here, we design and construct a light sheet fluorescence microscope with a coupled spectrometer for use in microlaser studies for combined high-resolution, high-speed imaging and WGM spectral analysis. The light sheet illumination profile and the decoupled geometry of excitation and emission hereby directly affect the lasing and sensing properties, mainly through geometric constraints and by light coupling effects. We demonstrate the basic working principle of microlaser spectroscopy under light sheet excitation and measure the absolute refractive index within agarose and in zebrafish tail muscle tissue. We further analyze the light coupling conditions that lead to the occurrence of two separate oscillation planes. These so-called cross modes can be scanned around the entire microlaser surface, which allows to estimate a surface-averaged refractive index profile of the microlaser environment.
    cm=eim(π2θ0)ikq(kr0dm)2k2w2+i2kq21+i2qkw2,

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    Ross C. Cowie, Marcel Schubert, "Light sheet microscope scanning of biointegrated microlasers for localized refractive index sensing," Photonics Res. 12, 1673 (2024)
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