Gichka Tsutsumanova

Plasmon-Enhanced Sub-Wavelength Laser Ablation: Plasmonic Nanojets

In response to the incident lights electric field, the electron density oscillates in the plasmonic hotspots producing an electric current. Associated Ohmic losses raise the temperature of the material within the plasmonic hotspot above the melting point. A nanojet and nanosphere ejection can then be observed precisely from the plasmonic hotspots.

Conditions for Loss Compensation of Surface Plasmon Polaritons Propagation on a Metal/Gain Medium Boundary

One way to compensate for the surface plasmon polariton (SPP) propagation losses is to use a gain medium. However, simply ensuring high enough gain is not sufficient because it may violate the bounded character of the wave. Therefore, a detailed theoretical analysis is needed for the determination of the conditions for lossless or amplified SPP propagation. Here presented is an exact theoretical analysis of the SPP propagation in the case of an infinite metal/gain medium boundary. It is shown that the conditions for lossless/amplified SPP propagation can be conveniently examined and presented as a simply connected region in the complex plane of the gain medium dielectric function. Effective and minimum gain parameters are introduced, which facilitates the simultaneous analyses of different gain media/metals combinations. The practical application of these results is illustrated for several gain media/metal (silver, gold and aluminium) systems.

Note: Simple vacuum feedthrough for optical fiber with SubMiniature version A connectors at both ends

We present a simple way to insert an optical fiber, with existing standard SubMiniature version A connectors on both ends into a vacuum system. The fitting is tested in scanning electron microscope, at working pressures down to 2 × 10(-5) mbar for cathodoluminescent measurements. With slight modifications this fitting could be successfully adapted for optical fiber insertion into pressurized systems.

Microstructure and crack resistance of low carbon Cr-Ni and Cr-Ni-W steel after austempering

The microstructure of the low carbon Cr-Ni steel after slow cooling from austenization temperature represents a mix of granulated bainite with islands from carbon-rich martensite and carbon-poor austenite. After quick cooling throwing in salt bath from austenization temperature the microstructure is lath bainite. However, in the same treatment conditions, the microstructure of the low carbon Cr-Ni-W steel is different — clusters consist from lath ferrite and retained austenite, disposed in the frame of parent’s austenite grains. The cooling velocity has no effect upon the structure making. The impact toughness of the steel with tungsten content is bigger than the steel without tungsten.

BaTiO3-Based Glass-Ceramics: Microstructure and Phase Composition

BaTiO3 is a well-known dielectric material with numerous allotropic modifications and interesting electrical and mechanical properties. Two modifications of barium titanate are usually of practical interest – the cubic and tetragonal one. Due to their high dielectric constants they both find application as parts of capacitors, different sensors or transducers. The present work reports on the synthesis of oxide glasses with high concentrations of alkali and alkaline earth metals and varying ratios of sodium to aluminium oxide in which further the crystallization of BaTiO3 is envisaged. The glasses obtained were subsequently subjected to annealing above the glass-transition temperature which results in the precipitation of barium titanate with very high volume fractions. The identification of the phase composition was performed by X-ray diffraction which suggests the formation of cubic BaTiO3. The investigation of the microstructure by scanning electron microscopy revealed the presence of phase separation and further growth of barium titanate globular crystals in the unmixed regions.

Two dimensional polymerization of graphene oxide: Bottom-up approach

Abstract We demonstrate a bottom-up synthesis of structures similar to graphene oxide via a two dimensional polymerization. Experimental evidence and discussion are conveyed as well as a general framework for this two dimensional polymerization. The proposed morphologies and lattice structures of these graphene oxides are derived from aldol condensation of alternating three nucleophilic and three electrophilic centers of benzenetriol.

Laser characterization of the depth profile of complex refractive index of PMMA implanted with 50 keV silicon ions

The depth profile of the complex refractive index of silicon ion (Si+) implanted polymethylmethacrylate (PMMA) is studied, in particular PMMA implanted with Si+ ions accelerated to a relatively low energy of 50 keV and at a fluence of 3.2 × 1015 cm-2. The ion-modified material with nano-clustered structure formed in the near(sub)surface layer of a thickness of about 100 nm is optically characterized by simulation based on reflection ellipsometry measurements at a wavelength of 632.8 nm (He-Ne laser). Being of importance for applications of ion-implanted PMMA in integrated optics, optoelectronics and optical communications, the effect of the index depth profile of Si+-implanted PMMA on the profile of the reflected laser beam due to laser-induced thermo-lensing in reflection is also analyzed upon illumination with a low power cw laser (wavelength 532 nm, optical power 10 – 50 mW).

A simple method for determination of the density of granular materials

A simple experiment using low cost equipment for the determination of the density of granular materials, without immersing them in a liquid, is presented. It is based only on the ideal gas state equation, so it is a good experimental task for undergraduate and high school students.

Variable distance absolute reflectometry

In many interferometric applications the variation of the reflected light intensity due to the separation distance change between two optical systems is the raw signal from which some unknown parameters must be determined. We consider the general situation in which the signal offset and amplification, the initial separation, and the optical properties of one of the systems are unknown. Using some major results from the complex analysis we derive closed-form expressions that give the exact solution of the above inverse problem in terms of the signals Fourier coefficients. It is shown that the absolute reflectivity can be found unambiguously, while the initial separation and the reflectance phase are mutually correlated and one of these parameters can be found only if the other one is known.