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Optical resonators play an ubiquitous role in modern optics. A particular class of optical resonators is constituted by spherical dielectric structures, where optical rays are total internal reflected. Due to minimal reflection losses and to potentially very low material absorption, these guided modes, known as whispering gallery modes, can confer the resonator an exceptionally high quality factor Q, leading to high energy density, narrow resonant-wavelength lines and a lengthy cavity ringdown.doi:10.3390/s110100785 pmid:22346603 pmcid:PMC3274111 fatcat:xcmarxzuljginc4mccqq5ure4y
more »... These attractive characteristics make these miniaturized optical resonators especially suited as laser cavities and resonant filters, but also as very sensitive sensors. First, a brief analysis is presented of the characteristics of microspherical resonators, of their fabrication methods, and of the light coupling techniques. Then, we attempt to overview some of the recent advances in the development of microspherical biosensors, underlining a number of important applications in the biomedical field.
Glass photonics are widespread, from everyday objects around us to high-tech specialized devices. Among different technologies, sol-gel synthesis allows for nanoscale materials engineering by exploiting its unique structures, such as transparent glass-ceramics, to tailor optical and electromagnetic properties and to boost photon-management yield. Here, we briefly discuss the state of the technology and show that the choice of the sol-gel as a synthesis method brings the advantage of processdoi:10.3390/cryst7020061 fatcat:3o5obt5rxzbptjbfvfvmpn5ueq
more »... atility regarding materials composition and ease of implementation. In this context, we present tin-dioxide-silica (SnO 2 -SiO 2 ) glass-ceramic waveguides activated by europium ions (Eu 3+ ). The focus is on the photorefractive properties of this system because its photoluminescence properties have already been discussed in the papers presented in the bibliography. The main findings include the high photosensitivity of sol-gel 25SnO 2 :75SiO 2 glass-ceramic waveguides; the ultraviolet (UV)-induced refractive index change (∆n~−1.6 × 10 −3 ), the easy fabrication process, and the low propagation losses (0.5 ± 0.2 dB/cm), that make this glass-ceramic an interesting photonic material for smart optical applications.
Silicon Photonics and Photonic Integrated Circuits IV
Honkanen, Lorenzo Pavesi, Stefano Pelli, Proceedings of SPIE Vol. 9133 (SPIE, Bellingham, WA, 2014) Article CID Number. 2014, Society of Photo-Optical Instrumentation Engineers. ... Vivien Laurent Seppo Honkanen Lorenzo Pavesi Stefano Pelli xi Proc. of SPIE Vol. 9133 -10 s), "Title of Paper," in Silicon Photonics and Photonic Integrated Circuits IV, edited by Laurent Vivien, Seppo ...doi:10.1117/12.2070011 fatcat:3t5vvhgf4va7vany5xoyqsejc4
In this paper, we described a versatile two steps approach for the realization of silica inverse opals functionalized with DNA-aptamers labelled with Cy3 fluorophore. The co-assembly method was successfully employed for the realization of high quality inverse silica opal, whilst the inverse network was functionalized via epoxy chemistry. Morphological and optical assessment revealed the presence of large ordered domains with a transmission band gap depth of 32%, after the functionalizationdoi:10.3390/s18124326 fatcat:uzuxmsf7gre6npoecutrvkhjve
more »... dure. Finite Difference Time-Domain (FDTD) simulations confirmed the high optical quality of the inverse opal realized. Photoluminescence measurements evidenced the effective immobilization of DNA-aptamer molecules labelled with Cy3 throughout the entire sample thickness. This assumption was verified by the inhibition of the fluorescence of Cy3 fluorophore tailoring the position of the photonic band gap of the inverse opal. The modification of the fluorescence could be justified by a variation in the density of states (DOS) calculated by the Plane Wave Expansion (PWE) method. Finally, the development of the aforementioned approach could be seen as proof of the concept experiment, suggesting that this type of system may act as a suitable platform for the realization of fluorescence-based bio-sensors.
This study analyzes the capabilities of a LiNbO3 whispering gallery mode microdisc resonator as a potential bolometer detector in the THz range. The resonator is theoretically characterized in the stationary regime by its thermo-optic and thermal coefficients. Considering a Q-factor of 10 7 , a minimum detectable power of 20 μW was evaluated, three orders of magnitude above its noise equivalent power. This value opens up the feasibility of exploiting LiNbO3 disc resonators as sensitive room-temperature detectors in the THz range.doi:10.3390/s17020258 pmid:28134857 pmcid:PMC5336064 fatcat:qbiqws6yafe7pc2qwmio5aanv4
The knowledge of the carrier dynamics in nanostructures is of fundamental importance for the development of (opto)electronic devices. This is true for semiconducting nanostructures as well as for plasmonic nanoparticles (NPs). Indeed, improvement of photocatalytic efficiencies by combining semiconductor and plasmonic nanostructures is one of the reasons why their ultrafast dynamics are intensively studied. In this work, we will review our activity on ultrafast spectroscopy in nanostructuresarXiv:2008.04135v1 fatcat:fh4ggvbsszff5pdfdjm4dyjkbq
more »... ied out in the recently established EuroFEL Support Laboratory. We have investigated the dynamical plasmonic responses of metal NPs both in solution and in 2D and 3D arrays on surfaces, with particular attention being paid to the effects of the nanoparticle shape and to the conversion of absorbed light into heat on a nano-localized scale. We will summarize the results obtained on the carrier dynamics in nanostructured perovskites with emphasis on the hot-carrier dynamics and in semiconductor nanosystems such as ZnSe and Si nanowires, with particular attention to the band-gap bleaching dynamics. Subsequently, the study of semiconductor-metal NP hybrids, such as CeO_2-Ag NPs, ZnSe-Ag NPs and ZnSe-Au NPs, allows the discussion of interaction mechanisms such as charge carrier transfer and Förster interaction. Finally, we assess an alternative method for the sensitization of wide band gap semiconductors to visible light by discussing the relationship between the carrier dynamics of TiO_2 NPs and V-doped TiO_2 NPs and their catalytic properties.
Optical fiber sensors, thanks to their compactness, fast response and real-time measurements, have a large impact in the fields of life science research, drug discovery and medical diagnostics. In recent years, advances in nanotechnology have resulted in the development of nanotools, capable of entering the single cell, resulting in new nanobiosensors useful for the detection of biomolecules inside living cells. In this paper, we provide an application of a nanotip coupled with moleculardoi:10.3390/s150509666 pmid:25919369 pmcid:PMC4481987 fatcat:n6ixzd7stvdopeqcgsixq42ipq
more »... (MBs) for the detection of DNA. The MBs were characterized by hybridization studies with a complementary target to prove their functionality both free in solution and immobilized onto a solid support. The solid support chosen as substrate for the immobilization of the MBs was a 30 nm tapered tip of an optical fiber, fabricated by chemical etching. With this set-up promising results were obtained and a limit of detection (LOD) of 0.57 nM was reached, opening up the possibility of using the proposed nanotip to detect mRNAs inside the cytoplasm of living cells.
Glasses, in their different forms and compositions, have special properties that are not found in other materials. The combination of transparency and hardness at room temperature, combined with a suitable mechanical strength and excellent chemical durability, makes this material indispensable for many applications in different technological fields (as, for instance, the optical fibres which constitute the physical carrier for high-speed communication networks as well as the transducer for adoi:10.3390/app11104610 fatcat:xqnsrwckijgirijoy7xfudfnoa
more »... e range of high-performance sensors). For its part, ion-exchange from molten salts is a well-established, low-cost technology capable of modifying the chemical-physical properties of glass. The synergy between ion-exchange and glass has always been a happy marriage, from its ancient historical background for the realisation of wonderful artefacts, to the discovery of novel and fascinating solutions for modern technology (e.g., integrated optics). Getting inspiration from some hot topics related to the application context of this technique, the goal of this critical review is to show how ion-exchange in glass, far from being an obsolete process, can still have an important impact in everyday life, both at a merely commercial level as well as at that of frontier research.
Silicon Photonics and Photonic Integrated Circuits V
Silicon Photonics and Photonic Integrated Circuits IV
This paper presents a new alignment concept for the alignment of multichannel photonic intergrated circuits (PICs) using flexible photonic waveguides on one of the PICs that are positionable by integrated micro electro mechanical system (MEMS) actuators. The concept aims for high precision and high degree of assembly process automation. The proposed concept includes pre-alignment of both PICs on a common substrate followed by fine-alignment using the on-chip flexible waveguides and MEMSdoi:10.1117/12.2052430 fatcat:wyrgq2plw5b6hocwwifc46fpfu
more »... ality. This paper introduces the alignment approach and reports on the development and fabrication of suspended and mechanically flexible photonic waveguides. Single suspended waveguide beams and suspended arrays with two and four coupled parallel waveguide beams of different lengths (250 µm to 1000 µm) and different widths (18 µm to 34 µm) are designed and fabricated. After fabrication, waveguide beam fracturing is observed. The fabrication process has been extended by an additional under-etching step in order to reduce beam fracturing. The static out-of-plane deflection of the fabricated devices follows a specific profile with a dominating upward curvature resulting in a measured maximum out-of-plane deflection of 2 % of the length. The beam stiffness of the fabricated devices is measured and proves to be within the available force of microactuators.
Pr 3+ -Yb 3+ co-doped oxyfluoride glasses and glass-ceramics (GCs) containing LaF3 nanocrystals have been prepared to obtain NIR emission of Yb 3+ ions upon Pr 3+ excitation in the blue region of the visible spectrum. Two different compositions have been tested: 0.1-0.5 Pr-Yb and 0.5-1 Pr-Yb, in addition to Pr 3+ singly doped samples. The crystallization mechanism of the nano-GCs was studied by differential thermal analysis revealing that it occurs from a constant number of nuclei, the crystaldoi:10.3389/fmats.2016.00058 fatcat:qr3gvboigrfg3bn74vjxuj3upu
more »... rowth being limited by diffusion. High-resolution transmission microscopy demonstrated that phase separation acts as precursor for LaF3 crystallization and a detailed analysis of the chemical composition (EDXS) revealed the enrichment in RE 3+ ions inside the initial phase separated droplets, from which the LaF3 crystals are formed. The RE 3+ ions incorporation inside LaF3 crystals was also proved by photoluminescence measurements showing Stark splitting of the RE 3+ ions energy levels in the glass-ceramic samples. Lifetime measurements showed the existence of a better energy transfer process between Pr 3+ and Yb 3+ ions in the GCs compared to the as made glass. The highest value of energy transfer efficiency is 59% and the highest theoretical quantum efficiency is 159%, obtained for GCs 0.1-0.5 Pr-Yb treated at 620°C for 40 h.
An accurate description of the structural and chemical modifications of cerium oxide nanoparticles is mandatory for understanding their functionality in the applications. In this work we investigate the relation between local atomic structure, oxidation state, defectivity and size in cerium oxide nanoparticles with variable diameter below 10 nm, using X-ray absorption fine structure analysis in the near and extended energy range. The nanoparticles are prepared by physical methods underdoi:10.1088/1361-6528/aa926f pmid:29016361 fatcat:ehc4vi4h3rh7jm6rbvcpmtgj3a
more »... d conditions and analyzed in morphology and crystalline quality by high resolution transmission electron microscopy. We resolve here an important question on the local structure of cerium oxide nanoparticles: we demonstrate a progressive contraction in the Ce-O interatomic distance with decreasing nanoparticle diameter and we relate the observed effect to the reduced dimensionality. The contraction is not significantly modified by inducing a 4-6% higher Ce 3+ concentration through thermal annealing in high vacuum. The consequences of the observed average cation-anion distance contraction on the properties of the nanoparticles are discussed.
Silicon Photonics and Photonic Integrated Circuits V
Several 3-D multilayer silicon photonics platforms have been proposed to provide densely integrated structures for complex integrated circuits. Amongst these platforms, great interest has been given to the inclusion of silicon nitride layers to achieve low propagation losses due to their capacity of providing tight optical confinement with low scattering losses in a wide spectral range. However, none of the proposed platforms have demonstrated the integration of active devices. The problem isdoi:10.1117/12.2227590 fatcat:wqld7z6i6rhtvpdf7ltbrp4nli
Andrea Barucci, Franco Cosi and Stefano Pelli defined the investigated test case, performed the experimental activity and guided the individuation of the flow regimes. Giancarlo C. ...doi:10.3390/fluids2010008 fatcat:ngbol5kpkndnvhnlespjldwno4
Optical fibre micro/nano tips (OFTs), defined here as tapered fibres with a waist diameter ranging from a few microns to tens of nanometres and different tip angles (i.e., from tens of degrees to fractions of degrees), represent extremely versatile tools that have attracted growing interest during these last decades in many areas of photonics. The field of applications can range from physical and chemical/biochemical sensing—also at the intracellular levels—to the development of near-fielddoi:10.3390/opt1020017 fatcat:hidtvcmhdnaadnpa3aadnspjva
more »... s for microscope imaging (i.e., scanning near-field optical microscopy (SNOM)) and optical interrogation systems, up to optical devices for trapping and manipulating microparticles (i.e., optical tweezers). All these applications rely on the ability to fabricate OFTs, tailoring some of their features according to the requirements determined by the specific application. In this review, starting from a short overview of the main fabrication methods used for the realisation of these optical micro/nano structures, the focus will be concentrated on some of their intriguing applications such as the development of label-based chemical/biochemical sensors and the implementation of SNOM probes for interrogating optical devices, including whispering gallery mode microcavities.
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