Search results for "photonics"
showing 10 items of 802 documents
Purcell Enhancement and Wavelength Shift of Emitted Light by CsPbI3 Perovskite Nanocrystals Coupled to Hyperbolic Metamaterials
2020
Manipulation of the exciton emission rate in nanocrystals of lead halide perovskites (LHPs) was demonstrated by means of coupling of excitons with a hyperbolic metamaterial (HMM) consisting of alternating thin metal (Ag) and dielectric (LiF) layers. Such a coupling is found to induce an increase of the exciton radiative recombination rate by more than a factor of three due to the Purcell effect when the distance between the quantum emitter and HMM is nominally as small as 10 nm, which coincides well with the results of our theoretical analysis. Besides, an effect of the coupling-induced long wavelength shift of the exciton emission spectrum is detected and modeled. These results can be of i…
Optical analysis to predict outcomes after implantation of a double intraocular lens magnification device.
2007
Purpose To analyze the effect of different optical parameters of the eye on the outcomes of implantation of a double intraocular lens (IOL) magnification device in patients with low vision. Setting Fundacion Oftalmologica del Mediterraneo, Valencia, Spain. Methods The eye's refraction and magnification before and after surgery were evaluated using a theoretical eye model based on paraxial optics approximation. Four parameters on which refraction and magnification are dependent were evaluated: anterior chamber depth (ACD), axial length (AL), mean keratometry (Km), and the distance between the 2 implanted IOLs. The 4 variables were analyzed separately in the first stage. Next, different combi…
Real-world Adherence and Persistence with Bisphosphonate Therapy in Postmenopausal Women: A Systematic Review
2018
Abstract Purpose Bisphosphonate therapy is a well-established and effective treatment for postmenopausal osteoporosis and the prevention of osteoporotic fracture. However, poor adherence to and poor persistence with bisphosphonate therapy may reduce its benefits. Previous studies have documented the poor rates of adherence and persistence among postmenopausal women with osteoporosis. The objective of this systematic literature review was to evaluate adherence, persistence, and the impact of adherence and persistence on fracture risk in postmenopausal women with diagnosed osteoporosis. Methods Articles eligible for review included observational studies of the real-world use of bisphosphonate…
Fundamental limits for transmission modulation in VO2 metasurfaces
2022
The interest in dynamic modulation of light by ultra-thin materials exhibiting insulator–metal phase transition, such as VO 2 , has rapidly grown due to the myriad industrial applications, including smart windows and optical limiters. However, for applications in the telecommunication spectral band, the light modulation through a thin VO 2 film is low due to the presence of strong material loss. Here, we demonstrate tailored nanostructuring of VO 2 to dramatically enhance its transmission modulation, reaching a value as high as 0.73, which is 2 times larger than the previous modulation achieved. The resulting designs, including free-topology optimization, demonstrate the fundamental limit i…
Manipulation of emitted light by structured lead halide perovskite nanocrystals for photonics applications
2021
Historically, active materials in photonic integrated circuits (PICs) have been implemented using III-V semiconductors, glasses, and ferroelectrics doped with rare-earth ions. However, there is a low-cost alternative based on (nano)materials synthesized using colloidal chemistry techniques. Their use in colloidal suspensions allows for the easy integration into any optical architecture via coating or printing techniques. The structure of perovskite nanocrystals (PNCs) are compounds with general formula ABX3, being A an inorganic or organic bulky cation, B a metal cation such as Pb2+ or Sn2+ and X the halide anion. In this context, all inorganic CsPbX3 (with X = Cl, Br, I) PNCs have recently…
Etude en champ proche et en champ lointain de composants périodiquement nanostructurés : cristaux photoniques et tamis à photons
2004
Recently, a new class of optical components is appeared. Its main characteristic is to be formed by a periodical sub-wavelength pattern, leading to the apparition of a spectral domain where propagation of light inside the structure is forbidden -- a photonic bandgap. This work is devoted to the study in the near- and far-field of two kinds of periodical optical components: photonic crystals (PCs) and nanostructured metallic films that exhibit the so-called enhanced transmission. First, we study two-dimensional PCs with a scanning near-field optical microscope (SNOM) in collection mode. With this SNOM, we directly map the intensity distribution inside PC-based microcavities. We also evidence…
Optical and electronic properties of the two-dimensional materials InSe, WSe2 and MoS2
2017
El camp dels materials bidimensionals ha atret recentment l’atenció de la comunitat científica. Les propietats particulars que aquests materials presenten quan el seu espessor és reduït fins l’escala nanomètrica permeten preveure el seu potencial per a aplicacions de recerca, tant fonamental com tecnològica, en una varietat de camps que inclou la catàlisi, l’emmagatzematge d’energia, la detecció, els dispositius optoelectrònics i la informació quàntica. Aquesta tesi presenta l’estudi de les propietats òptiques i electròniques de diferents materials van der Waals bidimensionals: les àmpliament estudiades formes bidimensionals dels dicalcogenurs de metals de transició MoS2 i WSe2, i les menys…
Radiation Response of Ce-Codoped Germanosilicate and Phosphosilicate Optical Fibers
2016
We report an experimental investigation on the effects of Ce-codoping in determining the radiation response of germanosilicate and phosphosilicate Optical Fibers (OFs) in the UV-Visible domain and up to doses of $1~\hbox{MGy}({\rm SiO}_{2})$ . We show that the addition of Ce strongly impacts the Radiation Induced Attenuation (RIA) of both types of fibers. In the first case the radiation induced losses increase, whereas in the second one decrease. By combining the online RIA measurements with the Electron Paramagnetic Resonance (EPR) ones, we are able to infer the basic microscopic mechanisms taking place under irradiation, which involve the cerium codopant and some of the known Ge-related o…
Temporal spying and concealing process in fibre-optic data transmission systems through polarization bypass
2014
Recent research has been focused on the ability to manipulate a light beam in such a way to hide, namely to cloak, an event over a finite time or localization in space. The main idea is to create a hole or a gap in the spatial or time domain so as to allow for an object or data to be kept hidden for a while and then to be restored. By enlarging the field of applications of this concept to telecommunications, researchers have recently reported the possibility to hide transmitted data in an optical fibre. Here we report the first experimental demonstration of perpetual temporal spying and blinding process of optical data in fibre-optic transmission line based on polarization bypass. We succes…
Investigation of Coating Impact on OFDR Optical Remote Fiber-Based Sensors Performances for Their Integration in High Temperature and Radiation Envir…
2016
The response of optical frequency-domain reflectometry-based temperature sensors is here investigated in harsh environments (high temperature, high radiation dose) focusing the attention on the impact of the fiber coating on the sensor performances in such conditions. Our results demonstrate that the various coating types evolve differently under thermal treatment and/or radiations, resulting in a small (<5%) change in the temperature coefficient of the sensor. The identified procedure, consisting of a prethermal treatment of the fiber at its maximum coating operating temperature, is here verified up to 150 °C for higherature acrylate and up to 300 °C for polyamide coating. This method allo…