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.
This work relies on the development of a sensorized medical needle with an all-optical guidance (Lab in a Needle)
system for epidural space identification. The device is based on the judicious integration of a Fiber Bragg grating sensor
inside the lumen of an epidural needle to discriminate between different types of tissue and thus providing continuous
and real time measurements of the pressure experienced by the needle tip during its advancement. Experiments carried
out on an epidural training phantom demonstrate the validity of our approach for the correct and effective identification
of the epidural space.
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.
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.
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.
This work deals with a novel Lab-on-Fiber biosensor able to detect in real time thyroid carcinomas biomarkers. The device is based on a gold nanostructure supporting localized surface plasmon resonances (LSPR) directly fabricated on the fiber tip by means of electron beam lithography and lift-off process. Following a suitable chemical and biological functionalization of the sensing area, human Thyroglobulin has been detected at nanomolar concentrations. Also, compatibility with full baseline restoration, achieved through biomarkers/bioreceptors dissociation, has been demonstrated.
We recently introduced a reliable fabrication process enabling the integration of dielectric and metallic nanostructures directly on the tip of optical fibers1. It involves conventional deposition and nanopatterning techniques (typically used for planar devices fabrication) suitably adapted to directly operate on the fiber tip. By using this approach, and with a view towards possible applications, here we demonstrate the realization of different technological platforms based on the integration on the fiber facet of periodic and quasi-periodic metallo-dielectric nanostructures supporting localized surface plasmon resonances, that can be used for chemical and biological sensing as well as polarization sensitive devices.
In this work, an ultra compact in line fiber optic Fabry-Perot interferometer is presented. The interferometric structure consists of a thin (< 1 μm) amorphous silicon layer in line integrated into a standard single mode optical fiber by means of an electric arc discharge technique. The device exhibits low loss (1.46 dB) and high interference fringe visibility (~ 30% in linear scale) both in reflection and transmission due to the high refractive index contrast between silica and α-Si. A high linear temperature sensitivity up to 75 pm/°C is demonstrated in the range 15-52 °C. The proposed device is simple, compact, cost effective and attractive for point monitoring sensing application in ultra-high temperature sensing in harsh environments.
This work provides numerical and experimental evidence that a significant difference exists between bulk and surface sensitivities in nanodevices based on Rayleigh anomalies (RAs) when employed for sensing the surrounding refractive index. In particular, recently proposed sensing schemes based on RAs in optical nanogratings are shown to be applicable only in the presence of bulk analytes. In the presence of thin overlays of analytes, instead, the (surface) sensitivity deteriorates up to two orders of magnitude by comparison with its bulk value, as well as with typical surface sensitivities exhibited by sensors based on surface plasmon resonances. This aspect is of fundamental importance as it severely limits the practical applicability of these devices to chemical and label-free biological sensing.
We recently introduced a reliable fabrication process enabling the integration of dielectric and metallic nanostructures directly on the tip of optical fibers, involving conventional deposition and nanopatterning techniques suitably adapted to directly operate on the fiber tip1. By using this approach, we also demonstrated a first technological platform based on the integration, on the optical fiber tip, of 2D hybrid metallo-dielectric nanostructures supporting localized surface plasmon resonances, that can be efficiently used for label free chemical and biological sensing. In this contribution we want to emphasize the versatility of the proposed technological platform. In particular, we demonstrate how by acting on the numerous degrees of freedom it provides, we are able to improve the performances of our nanoprobes for label-free chemical and biological sensing applications. Finally, the possibility to create novel advanced devices by breaking the circular symmetry of the crystal nanostructure is also demonstrated.
We introduce a reliable fabrication process enabling the integration of dielectric and metallic nanostructures on the tip of
optical fibers. It involves conventional deposition and nanopatterning techniques typically used for planar devices, but
here adapted to directly operate on optical fiber tip. Following this approach, we demonstrate a first technological
platform based on the integration, onto the optical fiber tip, of two-dimensional (2D) hybrid metallo-dielectric
nanostructures supporting localized surface plasmon resonances (LSPR), that can be efficiently used for label free
chemical and biological sensing and as a microphone for acoustic wave detection.
We report the evidence of plasmonic-photonic resonances in hybrid metallo-dielectric quasi-crystal nanostructures
composed of aperiodically-patterned low-contrast dielectric slabs backed on a metal layer. Via both experimental and
numerical studies, we characterize these resonant phenomena with specific reference to the Ammann-Beenker (quasiperiodic,
octagonal) tiling lattice geometry, and investigate the underlying physics. In particular, we show that, by
comparison with standard periodic structures, a richer spectrum of resonant modes may be excited. Such modes are
characterized by a distinctive plasmonic or photonic behavior, discriminated by their field distribution. Concerning the
possible applications, we also explore the structure functionalization via nanosized high refractive index overlays (for
resonance tuning and quality-factor enhancement), as well as its surface sensitivity to deposition of nanolayers of
materials mimicking bio-molecular binding. Overall, our results indicate the possibility of exciting a wealth of resonant
modes with state-of-the-art quality factors and sensing/tuning efficiencies, of potential interest for the development of
high-performance optical devices for communications, energy and sensing applications.
PART ONE:
The "Lab on Fiber" concept envisions novel and highly functionalized technological platforms completely
integrated in a single optical fiber that would allow the development of advanced devices, components and sub-systems
to be incorporated in modern optical systems for communication and sensing applications. The realization of integrated
optical fiber devices requires that several structures and materials at nano and micro scale are constructed, embedded and
connected all together to provide the necessary physical connections and light-matter interactions.
This paper reviews the strategies, the main achievements and related devices in the "Lab on Fiber" roadmap
discussing perspectives and challenges that lie ahead.
PART TWO:
After having reviewed, in the previous part, the main results achieved in the "Lab o Fiber" roadmap through the
development of several wavelength-scale devices and components based on the lab on fiber concept, here we focus the
attention on new trends involving innovative nano-fabrication strategies enabling to exploit further intriguing photonic
and/or plasmonic phenomena at the forefront of optical research.
Novel complex fabrication techniques of "Lab-on-fiber" device at the nanoscale are here presented and discussed,
from advanced multi material stacks and drawing technique up to the use of nanotechnologies, including standard
lithographic tools as well as new nano-imprinting approaches.
In particular, for the first time, we report some preliminary results obtained by our multidisciplinary research group
concerning the design and fabrication of a 2D hybrid metallo-dielectric photonic crystal (PC) nanostructure, directly
realized by innovatively applying the electron beam lithography technique on the cleaved end of standard single mode
optical fibers.
A novel interrogation scheme for Tilted Fiber Bragg Gratings (TFBGs) sensors is here proposed based on single
wavelength time delay measurements. To this aim, the group delay of a weakly tilted TFBG has been characterized by
direct time domain measurement. The experimental characterization shows the capability of TFBGs to enable
superluminal and subluminal propagation of an optical pulse in optical fibers. The sharp group delay features of the
TFBGs are exploited for refractometric applications to detect the SRI variations by single wavelength time delay
measurements. The obtained preliminary results demonstrate the possibility to detect SRI changes by means of single
wavelength time delay measurements with a sensitivity enhanced in the range 1.33-1.40 with respect to previously
reported interrogation techniques.
In the last decade there has been an increasing interest for terahertz technology. The reasons of this increasing interest is
mainly due to its potential use in security applications with particular reference to drug and explosive detection. In this
framework, the appropriate integration of metamaterials with nanotechnologies looks very promising for the construction
of new compact low cost devices. Following this line of argument, we are exploring the possibility to combine the use of
nanocathodes as sources of electron beams with engineered metamaterial layers in order to deliver coherent tunable
terahertz radiation. More exactly, starting from a revised design of microwave sources, we discuss the issues related to
manufacture miniaturized planar devices taking advantage of some appropriate integration of post silicon technologies.
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