Photonic Nanojets and Microspheres

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Microspheres to enhance single molecule fluorescence detection

Despite recent progress in nanotechnologies, a fundamental limitation on the state-of-the-art is set by complex optical instrumentation, and/or expensive nanofabrication facilities. We demonstrate that commercially available dielectric microspheres offer a relevant cost-effective alternative.

Beating the diffraction barrier with microspheres

Quite surprisingly, we show that commercially available microspheres under focused Gaussian illumination can achieve three-axis optical confinement below the diffraction limit, with an observation volume significantly lower than the wavelength cube.

This phenomenon is used to significantly enhance the fluorescence from a single emitter and overcome the limits set by diffraction in microscopy. The concept has strong connections with solid immersion lenses, yet with a much simpler and cost-effective system. Microspheres open new opportunities for low-cost and highly parallel means to develop new microscopy techniques, with applications to biophotonics, plasmonics, and optical data storage.

Disposable objective lenses for single molecule FCS detection

Combination of a latex microsphere with a simple lens to form a high performance optical system. Viable single molecule FCS experiments at concentrations 1-1000 nM with different objectives costing less than $40 are demonstrated. This offers a simple and low-cost alternative to the conventional complex microscope objectives.

Multi-focus FCS with photonic nanojets arrays. An array of latex microspheres replaces the complex microscope objective commonly used in fluorescence microscopy. This realizes a novel regime where several focal spots are illuminated to detect the possible presence of a fluorescent molecule in one of them. The system is an efficient disposable lens element that enables single molecule sensitivity at low picomolar concentration. The simplicity of the design makes it perfect for integration in portable microfluidic readers.

Selected publications

  • P. Ghenuche, J. de Torres, P. Ferrand, J. Wenger, Multi-focus parallel detection of fluorescent molecules at picomolar concentration with photonic nanojets arrays, Appl. Phys. Lett. 105, 131102 (2014).
  • Ferrand P., Wenger J., Devilez A., Pianta M., Stout B., Bonod N., Popov E., Rigneault H., "Direct imaging of photonic nanojets", Opt. Express 16, 6930-6940 (2008) - PDF
  • Gérard D., Wenger J., Devilez A., Gachet D., Stout B., Bonod N., Popov E., Rigneault H., Strong electromagnetic confinement near dielectric microspheres to enhance single-molecule fluorescence, Opt. Express 16, 15297-15303 (2008). - PDF
  • Wenger J., Gérard D., Aouani H., Rigneault H., Disposable Microscope Objective Lenses for Fluorescence Correlation Spectroscopy Using Latex Microspheres, Anal. Chem. 80, 6800-6804 (2008). - PDF