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We present results on the implementation of Whispering Gallery Modes (WGM) biosensors and on the demonstration of a new detection method for WGM based sensors. We first present a functionalization procedure based on the DNA-aptamer sequence immobilization on WGM resonators, able to recognize specifically thrombin protein. The protein binding was optically characterized in terms of specificity in buffer solution and in 10% diluted human serum. When performing the above measurements, we have used the typical detection scheme for WGM resonator based sensors, which relies on tracking the resonance shift − by scanning with a tunable laser − when a change of the refractive index in the region probed by the WGM takes place. In the second part of the presentation we propose a new sensing approach based instead on monitoring the position of the laser line of a fiber ring laser having a WGM microsphere in its loop. We demonstrate that the induced shift is the same for the ring laser line and for the microsphere resonance. The proposed method requires simpler and cheaper equipment and may also improve the sensor resolution because the ring laser line is narrower than the microsphere WGM resonance.

13 pages; International audience; Coating of spherical microresonators is a very promising technique for optimizing their optical properties. Optical coatings are constituted by glasses, polymer, and glass ceramics, passive or activated by luminescent species, Glass ceramic activated by rare earth ions are nanocomposite systems that exhibit specific morphologic, structural and spectroscopic properties allowing to develop interesting new physical concepts, for instance the mechanism related to the transparency, as well as novel photonic devices based on the enhancement of the luminescence. At the state of art the fabrication techniques based on bottom-up and top-down approaches appear to be viable although a specific effort is required to achieve the necessary reliability and reproducibility of the preparation protocols. In particular, the dependence of the final product on the specific parent glass and on the employed synthesis still remain an important task of the research in material science. Looking to application, the enhanced spectroscopic properties typical of glass ceramic in respect to those of the amorphous structures constitute an important point for the development of integrated optics devices, including coating of spherical microresonators. Here we present a review regarding spherical microresonators coated by glass and glass-ceramic film activated by Er3+ ions. Er3+ ions appear to be embedded in a crystalline or amorphous environment and the lifetime dynamic is influenced by the geometry and by the morphology of the system. Photoluminescence results and morphologic properties are discussed for both amorphous and glass ceramic films.