We report on a innovative Lab on Fiber (LOF) dosimeter for ionizing radiation monitoring at ultra-high doses. The new dosimeter consists in a metallo-dielectric resonator at sub-wavelength scale supporting localized surface plasmon resonances realized on the optical fiber (OF) tip. The resonating structure involves two gold gratings separated by a templated dielectric layer of poly(methyl methacrylate) (PMMA). Two LOF prototypes have been manufactured and exposed, at the IRRAD Proton Facility at CERN in Geneva, to 23 GeV protons for a total fluence of 0.67x1016 protons/cm2 , corresponding to an absorbed dose of 1.8 MGy. Experimental data demonstrate the "radiation resistance" feature of the LOF devices and a clear dependence of the reflected spectrum on the total dose, expressed by a cumulative blue-shift of ~1.4 nm of the resonance combined with a slight increase of 0.16 dBm in the reflected spectrum. According to the numerical analysis and the literature, the main phenomenon induced by exposure to proton beam and able to explain the measured spectral behavior is the reduction of the PMMA thickness. Preliminary results demonstrated the potentiality of the proposed platform as dosimeter at MGy dose levels for High Energy Physics (HEP) experiments.
Microgel assisted lab-on-fiber optrodes, arising from the integration of multiresponsive microgels onto nanostructured optical fibers tip, are emerging as intriguing multifunctional devices exploitable in biomedical applications, especially for label-free molecule detection. We have recently demonstrated that the sensitivity range of these devices is strictly related to the microgel films characteristics, which can be controlled during the microgel deposition procedure, based on the dip coating technique. With the aim of optimizing the deposition procedure in terms of fabrication throughput, we evaluate each fabrication step (fiber dipping, rinsing, and drying), demonstrating that the overall deposition duration can be significantly reduced from 960 min (of the ‘standard’ procedure) to 31 min, without affecting the microgel film characteristics. The analysis has been carried out by means of both optical and morphological characterization, and validated through repeatability tests. Overall, our results set the stage for engineering microgel assisted miniaturized optrodes, enabling their possible exploitation in industrial applications.
We experimentally demonstrate a novel optical fiber label free optrode platform resulting from the integration between
two rapidly emerging technologies such as Lab-on-Fiber Technology (LOFT) and Microgel Photonics (MPs). The device
consists of a microgel (MG) layer painted on a metallic slabs supporting plasmonic resonances, directly integrated on the
optical fiber tip. A molecular binding event induces significant changes in the MG layer thickness (and consequently in
its 'equivalent' refractive index) resulting in an evident wavelength shift of the resonant feature. As a case of study,
glucose-responsive MGs have been synthesized by incorporating into the gel matrix boronic acid moieties, whose
interaction with glucose rules the driving forces for gel swelling. Our results pave the way for new technological routes
aimed to develop advanced label free fiber optic nanoprobes.
We experimentally demonstrate a novel multifunctional optical fiber probe resulting from the integration between two
rapidly emerging technologies such as Lab-on-Fiber and Microgel Photonics. The device consists of a microgel based
cavity formed by metallic slabs supporting plasmonic resonances, directly integrated on the optical fiber tip. By
exploiting the multiresponsivity of microgel systems, variations of temperature, PH, ionic strength, as well as molecular
binding events, make the cavity to ‘breath’, thus modulating the interference pattern in the reflection spectrum. The
microgel layer can be synthetized in such a way to obtain different thicknesses, corresponding to different operating
regimes, opening new avenues for the realization of advanced multifunctional nanoprobes.
Sub-wavelength metallo-dielectric gratings integrated on optical fibers tip and supporting plasmonic resonances were numerically investigated in their behavior as acousto-optical transducers. Different configurations have been analyzed and compared among them in terms of sensitivity, defined as reflectivity intensity variation (at fixed wavelength) with respect to dielectric layer thickness changes. Our results demonstrate that the maximum sensitivity is obtained when an interaction between different plasmonic modes occurs. Sensitivity enhancement up to a factor of 3 with respect to Fabry- Perot cavity like transducer with same materials and sizes can be achieved.
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