88 research outputs found
In-parallel polar monitoring of chemiluminescence emission anisotropy at the solid-liquid interface by an optical fiber radial array
Chemiluminescence (CL) detection is widely employed in biosensors and miniaturized analytical devices since it offers high detectability and flexible device design (there are no geometry requirements for the measurement cell, except the ability to collect the largest fraction of emitted photons). Although the emission anisotropy phenomenon for an emitting dipole bound to the interface between two media with different refractive index is well known for fluorescence, it is still poorly investigated for CL reactions, in which the excited-state reaction products can diffuse in solution before the photon emission event. In this paper, we propose a simple method for the realtime evaluation of the CL emission anisotropy based on a radial array of optical fibers, embedded in a poly(methyl methacrylate) semicylinder and coupled with a Charge-Coupled Device (CCD) camera through a suitable interface. The polar-time evolutions of the CL emission have been studied for catalyzing enzymes immobilized onto a solid surface (heterogeneous configuration) or free in solution (homogeneous configuration). Evidence of the anisotropy phenomenon is observed, indicating that the lifetime of the excited-state products of the enzyme-catalyzed reactions is shorter than the time required for their diffusion in solution at a distance at which the CL can be considered isotropic. These results open new perspectives in the development of CL-based miniaturized analytical devices
Planar coupling to high-Q lithium niobate disk resonators
We demonstrate optical coupling to high-Q lithium niobate disks from an integrated lithium niobate waveguide. The waveguides are made by proton exchange in X-cut lithium niobate substrate. The disks with diameter of 4.7 mm and thickness of 1 mm are made from commercial Z-cut lithium niobate wafers by polishing the edges into a spheroidal profile. Both resonance linewidth and cavity ringdown measurements were performed to calculate the Q factor of the resonator, which is in excess of 10(8). Planar coupling represents the most promising technique for practical applications of whispering gallery mode resonators
Rare-earth-activated glasses for solar energy conversion
The solar cells efficiency may be improved by better exploitation of the solar spectrum, making use of the down-conversion mechanism, where one high energy photon is cut into two low energy photons. The choice of the matrix is a crucial point to obtain an efficient down-conversion process with rare-earth ions. When energy transfer between rare earth ions is used to activate this process, high emission and absorption cross sections as well as low cut-off phonon energy are mandatory. In this paper we present some results concerning 70SiO2-30HfO2 glass ceramic planar waveguides co-activated by Tb3+/Yb3+ ions, fabricated by sol gel route using a top-down approach, and a bulk fluoride glass of molar composition 70ZrF4 23.5LaF3 0.5AlF3 6GaF3 co-activated by Pr3+/Yb3+ ion. Attention is focused on the assessment of the energy transfer efficiency between the two couples of rare earth ions in the different hosts
Single - and double energy swift and slow heavy ion irradiated optical waveguides in Er: Tungstene-Tellurite glass and BGO for telecom applications
The fabrication of broadband amplifiers in wavelength division multiplexing (WDM) around 1.55 m, as they exhibit large stimulated cross sections and broad emission bandwidth. Bi4Ge3O12 (eultine type BGO) - well known scintillator material, also a rare-earth host material, photorefractive waveguides produced in it only using light ions in the past. Recently: MeV N+ ions and swift O5+ and C5+ ions, too*. Bi12GeO20 (sillenite type BGO) - high photoconductivity and photorefractive sensitivity in the visible and NIR good candidate for real-time holography and optical phase conjugation, photorefractive waveguides produced in it only using light ions. No previous attempts of ion beam fabrication of waveguides in it
Sol–gel-derived glass-ceramic photorefractive films for photonic structures
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 process versatility regarding materials composition and ease of implementation. In this context, we present tin-dioxide–silica (SnO2–SiO2) glass-ceramic waveguides activated by europium ions (Eu3+). 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 25SnO2:75SiO2 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
M-line spectroscopic, spectroscopic ellipsometric and microscopic measurements of optical waveguides fabricated by MeV-energy N+ ion irradiation for telecom applications
Irradiation with N+ ions of the 1.5 - 3.5 MeV energy range was applied to optical waveguide
formation. Planar and channel waveguides have been fabricated in an Er-doped tungsten-tellurite
glass, and in both types of bismuth germanate (BGO) crystals: Bi4Ge3O12 (eulytine) and Bi12GeO20
(sillenite). Multi-wavelength m-line spectroscopy and spectroscopic ellipsometry were used for the
characterisation of the ion beam irradiated waveguides. Planar waveguides fabricated in the Er-doped
tungsten-tellurite glass using irradiation with N+ ions at 3.5 MeV worked even at the 1550 nm
telecommunication wavelength. 3.5 MeV N+ ion irradiated planar waveguides in eulytine-type BGO
worked up to 1550 nm and those in sillenite-type BGO worked up to 1330 nm
Cavity optomechanics on a microfluidic resonator with water and viscous liquids
Currently, optical- or mechanical-resonances are commonly used in
microfluidic research. However, optomechanical oscillations by light pressure
were not shown with liquids. This is because replacing the surrounding air with
water inherently increases the acoustical impedance and hence the associated
acoustical radiation-losses. Here, we bridge between microfluidics and
optomechanics by fabricating hollow bubble resonators with liquid inside and
optically exciting 100-MHz vibrations with only mW optical-input power. This
constitutes the first time that any microfluidic system is optomechanically
actuated. We further prove the feasibility of microfluidic optomechanics on
liquids by demonstrating vibrations on organic fluids with viscous-dissipation
higher than blood viscosity while measuring density changes in the liquid via
the vibration frequency shift. Our device will enable using cavity
optomechanics for studying non-solid phases of matter
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