About the role of phase matching between a coated microsphere and a tapered fiber: experimental study

nombre de pages 10International audienceCoatings of spherical optical microresonators are widely employed for different applications. Here the effect of the thickness of a homogeneous coating layer on the coupling of light from a tapered fiber to a coated microsphere has been studied. Spherical silica microresonators were coated using a 70SiO2 - 30HfO2 glass doped with 0.3 mol% Er3+ ions. The coupling of a 1480 nm pump laser inside the sphere has been assessed using a tapered optical fiber and observing the 1530-1580 nm Er3+ emission outcoupled to the same tapered fiber. The measurements were done for different coating thicknesses and compared with theoretical calculations to understand the relationship of the detected signal with the whispering gallery mode electric field profiles

Glass-based 1-D dielectric microcavities

We have developed a reliable RF sputtering techniques allowing to fabricate glass-based one dimensional microcavities, with high quality factor. This property is strongly related to the modification of the density of states due to the confinement of the gain medium in a photonic band gap structure. In this short review we present some of the more recent results obtained by our team exploiting these 1D microcavities. In particular we present: (1) Er3+ luminescence enhancement of the 4I13/2 → 4I15/2 transition; (2) broad band filters based on disordered 1-D photonic structures; (3) threshold defect-mode lasing action in a hybrid structure

Coherent emission from fully Er 3+ doped monolithic 1-D dielectric microcavity fabricated by rf-sputtering

All Er3+ doped dielectric 1-D microcavity was fabricated by rf sputtering technique. The microcavity was constituted by half wave Er3+ doped SiO2 active layer inserted between two Bragg reflectors consists of ten pairs of SiO2/TiO2 layers also doped with Er3+ ions. The scanning electron microscopy was used to check the morphology of the structure. Transmission measurements confirm the third and first order cavity resonance at 530 nm and 1560 nm, respectively. The photoluminescence measurements were obtained by optically exciting at the third order cavity resonance using 514.5 nm Ar+ laser with an excitation angle of 30°. The Full Width at Half Maximum of the emission peak at 1560 nm decrease with the pump power until the spectral resolution of the detection system of ∼1.0 nm. Moreover, the emission intensity presents a non-linear behavior with the pump power and a threshold at about 24 mW was observed with saturation of the signal at above 185 mW of pump power

Analysis of selected elements in water in the drinking water preparation plants in Belgrade, Serbia

Belgrade's water supply relies mainly on the River Sava and groundwater supply wells, which are located in the vicinity of the river and Ada Ciganlija. In this paper, the contents of aluminum, boron, chromium, manganese, cobalt, nickel, copper, zinc, arsenic, cadmium, barium and lead were analyzed in raw water as well as drinking water distributed by the Water Supply and Sewage of Belgrade. A total of 14 samples were examined from all water treatment plants that are part of the distribution system. The measurements were conducted using the inductively coupled plasma-mass spectrometry (ICP-MS) technique. The aim of this research was to examine the effectiveness of the drinking water preparation process in the plants belonging to the Water Supply and Sewage of Belgrade. The content of certain elements varies considerably in raw water (river and groundwater): the concentration of boron in river water is two to three times lower than the concentration in groundwater; the concentration of arsenic in river water is ten to twenty five times lower than the concentration in groundwater; the concentration of aluminum in all groundwater samples was below the detection limit of the instrument (0.50 μg/dm3), whilst in the river water the content of aluminum was about 50 μg/dm3 and the concentration of manganese in the river water was up to 10 times lower than the concentrations in groundwater. In all drinking water samples the concentration of the elements were bellow the maximum allowed levels according to the Serbian regulations. Correlation coefficients determined for boron, manganese, cobalt, nickel, copper, zinc, arsenic, barium and lead, which were analyzed in raw waters, show that four groups of elements can be distinguished. Boron, manganese, arsenic and barium are related to each other and probably have a common natural origin; copper and lead probably have a common anthropogenic origin; correlation of nickel and cobalt was observed, while zinc was not in correlation with any other element.U ovom radu ispitivan je sadržaj aluminijuma, bora, hroma, mangana, kobalta, nikla, bakra, cinka, arsena, kadmijuma, barijuma i olova u sirovoj vodi i vodi za piće koju koristi, odnosno isporučuje potrošačima Javno komunalno preduzeće Beogradski vodovod i kanalizacija. Ispitano je ukupno 14 uzoraka sa svih pogona za pripremu vode koja su u sastavu Beogradskog vodovoda i kanalizacije. Analiza uzoraka je rađena primenom indukovano spregnute plazme sa masenom spektrometrijom. Cilj istraživanja je bio da se ispita efikasnost procesa za pripremu vode za piće koji se primenjuju u pogonima Beogradskog vodovoda i kanalizacije. Iako su koncentracije pojedinih elemenata u sirovoj vodi bile u širokom opsegu vrednosti i znatno se razlikovale u podzemnim i rečnim vodama, u uzorcima vode za piće koncentracije svih ispitivanih elemenata bile su niže od maksimalno dozvoljenih koncentracija propisanih zakonskom regulativom Republike Srbije

Whispering gallery mode microresonators : Fundamentals and applications

nombre de pages 54International audienceConfinement of light into small volumes has become an essential requirement for photonic devices; examples of this trend are provided by optical fibers, integrated optical circuits, semiconductor lasers, and photonic crystals. Optical dielectric resonators supporting Whispering Gallery Modes (WGMs) represent another class of cavity devices with exceptional properties, like extremely small mode volume, very high power density, and very narrow spectral linewidth. WGM are now known since more than 100 years, after the papers published by John William Strutt (LordRayleigh), but their importance as unique tools to study nonlinear optical phenomena or quantum electrodynamics, and for application to very low- threshold microlasers as well as very sensitive microsensors, has been recognized only in recent years. This paper presents a review of the field of WGM resonators, which exist in several geometrical structures like cylindrical optical fibers, microspheres, microfiber coils, microdisks, microtoroids, photonic crystal cavities, etc. up to the most exotic structures, such as bottle and bubble microresonators. For the sake of simplicity, the fundaments of WGM propagation and most of the applications will be described only with reference to the most common structure, i.e. microspherical resonators

Erbium activated silica – hafnia coated microspheres

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Erbium doped silica microspheres for lasing applications

International audienceSilica microspheres were made by melting the tip of a standard telecom fiber. They were coated using a dip coating apparatus with a 70% SiO2 – 30 HfO2 sol-gel derived glass activated by 0.3 % mol of Er3+. The whispering gallery modes of the coated resonator were studied using a full taper – microsphere coupling setup. Upon excitation at 1480 nm sharp peaks in the wavelength range from 1540-1565 nm were observed pertaining to the lasing modes of the microresonator

Whispering gallery modes in coated silica microspheres

6 pagesInternational audienceSilica microspheres were made by melting the tip of a standard telecom fiber and were coated with a 70SiO2 - 30 HfO2 sol-gel derived glass activated by 0.3 mol % of Er3+ ions. The samples were coated using a dip coating apparatus. The thickness of the coating was estimated to be around 1 μm. The whispering gallery modes of the coated resonator were studied using a full taper - microsphere coupling setup. Upon excitation at 1480 nm sharp peaks at wavelengths 1540- 1565 nm were observed. They were attributed to the whispering gallery modes of the microsphere falling in the wavelength range of the erbium emission