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In this work we review in part of the whispering-gallery-mode (WGM) lasers in Er3+-doped silica glass microspheres (μS) towards integration in silicon-on-insulator (SOI) slotted photonic crystal waveguides. The Er3+-doped silica glass μS with suitable diameters fabricated by using an electrical discharge method. The single-mode optical tapered fibers were used to guide the pumped laser into the μS surface and collect the resulting lasing emission. The observation of WGM at telecom regime is quantified. With the presented scheme, the selective single- or multi-emitted modes of the μS laser can be obtained by adjusting the coupling gap between the collection tapered fiber and the μS surface. To overcome the collection tapered fiber’s vibration at close range of the coupling gap, the guiding and coupling losses, while being compact enough to fit with complementary metal oxide semiconductor (CMOS) device, the integration of μS with SOI slotted photonic crystal waveguides is proposed and modeled with the help of finite-difference time-domain (FDTD) simulations. The designed structures may find application for the promising photonic devices such as the ultrahigh sensitivity sensors, the lasing sources, and towards advanced quantum communications.

Syntactic foam is a solid insulation material, featuring a foam-like structure. It's a composition of hollow microspheres and a polymeric matrix material. In this study it consists of glass microspheres and an epoxy resin matrix. The present paper deals with the influence of modified inner interfaces (achieved by silane-coated glass microspheres in order to improve the adhesion quality between the glass microspheres and the epoxy resin matrix) on the electrical properties of the material. The experiments show that the silane-coating (also known as silanization) has a positive influence on the breakdown field strength under electrical ac and dc short term stress. The experiments are conducted for different degrees of filling of the glass microspheres (10 vol.% ... 50 vol.%). It is shown, that the influence of the silanization becomes more significant with higher degree of filling. The life time of the material under electrical ac as well as dc stress can also be improved by a silanization. The dielectric properties (loss factor and relative permittivity) are not influenced by a silanization. Measurements of the viscosity of syntactic foam verify that a silanization reduces the viscosity of the uncured, liquid material during the manufacturing process. Hereby, an improvement of the material's production quality can be achieved at high microspheres' filling degrees.

This paper reports the first observation of chromatic and intensity optical bistability (OB) in a commercial, active, phosphate glass (Schott IOG-2) microsphere driven by thermal avalanche at room temperature. This is, to the best of our knowledge, the first report of simultaneous intensity OB (at multiple wavelengths) and chromatic OB in a single material.

The paper presents research data of the UV-radiation effect on the structure formation and physical-mechanical properties of paint coatings formed from the industrial EP-773 two-component epoxy enamel. The coatings have been modified with active hollow glass microspheres (Q-cel 6048) and have been irradiated with UV light (207 nm). A relevance of the work associated with the need of improvement coating producing technologies and development protective paints with required performance characteristics. By the method of scanning electron microscopy it was found that addition of the microspheres in the industrial EP-773 two-component epoxy enamel leads to decrease in a number of micro cracks and their extending in a volume of paint coatings. It is shown that hardness of paint coatings with the hollow glass microspheres is higher. It has been established that hollow glass microspheres improve the hiding power of the paint coatings, while maintaining a high level of an adhesion and an impact strength, thereby contributing to save paint coatings and to increase their service period due decreasing in the amount of corrosion products on their surfaces. It is obtained that effect of the UV radiation (wavelength 207 nm) on the surface of paint coatings formed from the industrial EP-773 two-component epoxy enamel modified with active fillers leads to structure destruction primarily near microspheres due to occurring extra internal stresses and promotes to derivation of polymer crosslinking due to the successive addition of free-radical building blocks. The experimental date indicate that UV irradiation of coatings surface deposited from EP-773 two-component epoxy enamel with glass microspheres promotes forming uniformly, dense and non-porous paint coatings with decreased hardness but with extra corrosion protection.

Polymeric materials and composites on their matrix are increasingly used in the electronics and electrotechnical industry, mainly as insulating elements, construction and housing electronic equipment. Modification of classic plastics using fillers and polymer recyclate allows the production of new composite materials with good electrical, exploitive and processing properties. It also creates opportunities for the rational use of recyclates generated from waste. The article describes the electrical properties of the new polymeric composites of polypropylene (PP), recycled of polyvinyl butyral (PVB rec), and fillers such as glass microspheres (GB) and glass powder (GP). On the basis of studies, the potential use of new materials in electronics and electrical engineering were determined.

The paper is a review on modelling and experimental results regarding microsphere resonators. The applications of the whispering-gallery-modes (WGMs) resonances in conventional glass microspheres to perform chemical spectroscopy, biomedical sensing, low threshold lasing are recalled. The behaviour of silica microsphere coated via silica hafnia 70SiO 2 -30HfO 2 and activated with 0.3% mol Er 3+ for NIR operation is described. The feasibility of amplifying systems, operating in Mid-IR wavelength and based on Er 3+- doped Ga 5 Ge 20 Sb 10 S 65 chalcogenide microspheres coupled to tapered a fiber is discussed. The investigation has been performed via a dedicated 3D numerical model, based on the coupled mode theory and solving the rate equations. The code includes the transitions among the erbium energy levels, the amplified spontaneous emission and the most important secondary transitions pertaining to the ion–ion interactions. The model follows the particle swarm optimization (PSO) approach, allowing both the amplifying system optimization and to perform the microsphere glass spectroscopy.

We demonstrate that the super-resolution imaging of a commercial Blu-ray® disk containing a one-dimensional array of 200 nm width stripes separated by 100 nm width grooves can be achieved using high-index microspheres in a liquid environment. By using barium titanate glass microspheres (2–20 μm diameters) with index around 1.9 totally immersed in isopropanol with index 1.37 we demonstrate better than λ/6 far field resolution, where λ= 600 nm is the peak wavelength of the white-light illumination system. The results of this work can be used in biomedical microscopy, microfluidics and nanophotonics applications for imaging individual cells and/or nanoparticles in a liquid environment.

We show that high index (∼2.0) barium titanate glass microspheres are perfect candidates for applications involving liquid immersion due to their high quality (∼104) whispering gallery resonances evanescently excited in compact (4–15 µm) spherical resonators.

High-Q whispering gallery mode resonators (WGMs) made both in glasses or crystals attract growing interest not only for the investigation of fundamental processes but also for the implementation of advanced photonics devices and biological sensors [1]. For practical applications of WGM resonators the crucial issue is the implementation of an efficient and robust coupling scheme. Fiber taper based couplers are particularly efficient and flexible but strongly lack of the necessary robustness. Prism coupling technique, which involves free space beams, is typically used to efficiently couple light in crystalline resonators. Planar waveguide coupling to glass microspheres and more recently to high-Q lithium niobate resonators [2] has been also demonstrated. Finally an alternative known coupler is based on angle polished fibers [3]. The tip of an optical fiber is polished according to a proper angle θ so that the evanescent field after the total internal reflection has the same propagation constant of the resonator mode we want to excite. The application of this method is limited by the availability of fibers with the proper refractive index. In this work we propose the alternative use of robust angle polished waveguides which can be made on a number of different substrates, which, in turn, can be selected with the proper index in order to fulfil the phase matching condition with the resonator. The simple equation θ=acos(n WGM /n WG ) holds, where n WGM and n WG are the WGM and the waveguide effective indices, respectively.

We report the manufacturing and optical characterization of chalcogenide microsphere. We show that high-Q modes of chalcogenide glass microspheres can be efficiently excited using a tapered fiber.

We theoretically study and experimentally demonstrate a novel fibered multicolor light source in the range 320-850 nm in Er3+ doped ZBLALiP and 405-850 nm in Er3+ doped ZBNA fluoride glass microspheres.

We theoretically study and experimentally demonstrate thermally induced optical bistability in Yb3+-Er3+ phosphate glass microspheres at 295 K. Thermal avalanche in Yb3+ ions is concomitant with bistability in Er3+ fluorescence and lasing behavior, and chromatic switching.

We report on a method of assigning the mode indices to whispering-gallery modes observed in the fluorescence spectra of Er3+doped tellurite glass microspheres.

Commercial sources of conductive silicone gaskets for electromagnetic interference (EMI) shielding filled with silver-plated glass microspheres were highly stable under conditions of severe vibration and intense simulated electromagnetic pulse (EMP). The results are in contrast to data published by C.H. Kuist (1977) and may demonstrate a considerable advancement in EMI gasket and conductive filler manufacturing technologies. The data showed there is no longer reason for concern over vibration and EMP stabilities of silver-glass gaskets. >