Ultra-short stripe microlasers fabricated with a focused ion beam etching technique.

Fabry-Perot (FP) lasers with a cavity length shorten down to 50 µm were investigated. One or two laser mirrors were formed by focused ion beam etching. InGaAs quantum dots of high density were used as the laser active region.

Diffusive Formation of Au/Ag Alloy Nanoparticles of Governed Composition in Glass.

For the first time we show that the introduction of silver ions in the glass containing gold nanoparticles (NPs) and additional heat treatment of the glass in the air lead to the formation of Au/Ag alloy NPs. The proposed approach makes it possible to position localized surface plasmon resonance of the NPs by selecting the heat treatment temperature, which determines the silver proportion in the alloy NPs. This allows for expanding customizability of NPs for applications in surface-enhanced Raman scattering spectroscopy, catalysis and biochemistry.

Poling of Glasses Using Resistive Barrier Discharge Plasma.

A technique for poling of glasses using a resistive barrier discharge plasma in the atmosphere in a gap of hundreds of microns is presented. Measurements of the polarization current, second harmonic generation, and IR spectra of poled soda-lime glass slides show that voltage sufficient to ignite plasma discharge provides efficient poling, whereas for lower voltages the poling effect is close to zero. We attributed this to the large number of hydrogen/hydronium ions generated from atmospheric water vapor by the plasma discharge in the gap, which penetrate into the glass.

How Activity Series Governs Transformation of Metal Nanoparticles in Glasses.

It has been experimentally shown for the first time that metallic copper in glasses can play the role of a reducing agent for other metallic ions, in particular, resulting in the formation of metal nanoparticles. Silver ions have been introduced into an alkali silicate glass containing copper nanoparticles by ion exchange. This has resulted in the formation of silver nanoparticles accompanied by the disappearance of copper nanoparticles initially contained in the glass.

Raman Scattering Study of Amino Acids Adsorbed on a Silver Nanoisland Film.

We studied the surface-enhanced Raman spectra of amino acids -alanine and -serine and their mixture on silver nanoisland films (SNF) immersed in phosphate-buffered saline (PBS) solution at millimolar amino acid concentrations. It is shown that the spectra from the amino acid solutions differ from the reference spectra for microcrystallites due to the electrostatic orientation of amino acid zwitterions by the metal nanoisland film. Moreover, non-additive peaks are observed in the spectrum of the mixture of amino acids adsorbed on SNF, which means that intermolecular interactions between adsorbed amino acids are very significant.

Giant Enhancement of Optical Second Harmonic in Poled Glasses by Cold Repoling.

For the first time, we demonstrated that additional poling at room temperature (cold repoling) of a soda-lime glass thermally poled in open anode configuration causes an increase of the optical second harmonic signal by more than an order of magnitude. Performed experiments allow relating this increase in the optical nonlinearity of the glass to the orientation of hydrogenated dipoles in the vicinity of the glass surface. This indicates that both frozen electric field and dipole orientation are responsible for the nonlinearity of thermally poled alkali-containing glasses.

Power Spectral Density Analysis for Optimizing SERS Structures.

The problem of optimizing the topography of metal structures allowing Surface Enhanced Raman Scattering (SERS) sensing is considered. We developed a model, which randomly distributes hemispheroidal particles over a given area of the glass substrate and estimates SERS capabilities of the obtained structures. We applied Power Spectral Density (PSD) analysis to modeled structures and to atomic force microscope images widely used in SERS metal island films and metal dendrites.

Visualization of Spatial Charge in Thermally Poled Glasses via Nanoparticles Formation.

It is shown for the first time that the vacuum poling of soda-lime silicate glass and the subsequent processing of the glass in a melt containing silver ions results in the formation of silver nanoparticles buried in the subanodic region of the glass at a depth of 800-1700 nm. We associate the formation of nanoparticles with the transfer of electrons from negatively charged non-bridging oxygen atoms to silver ions, their reduction as well as their clustering. The nanoparticles do not form in the ion-depleted area just beneath the glass surface, which indicates the absence of a spatial charge (negatively charged oxygen atoms) in this region of the vacuum-poled glass.

Stable in Biocompatible Buffers Silver Nanoisland Films for SERS.

We investigated the stability of silver nanoisland films, which were formed on glass surface by the method of out-diffusion, in biocompatible buffers and the applicability of the films in surface enhanced Raman scattering (SERS). We have shown that silver nanoisland films are stable in one of the most widespread in biological studies buffer-phosphate buffer saline (PBS), and in 1:100 water-diluted PBS, in the PBS-based buffer, in which NaCl is replaced by the same amount of NaClO, and in acidic phosphate buffer. At the same time, the replacement of NaCl in PBS by N(CH)Cl leads to the degradation of the nanoislands.

Controlled metallization of ion-exchanged glasses by thermal poling.

We present studies of the formation of silver nanoparticles (NPs) in silver-sodium ion-exchanged glasses by a combination of thermal poling and nanosecond pulsed laser irradiation at 355 nm. In poling, silver ions drift deeper into the glass and become separated from the glass surface by a poled layer depleted in cations. Performed measurements have indicated poling-induced broadening of silver ions depth distribution.

SEM-visualization of a spatial charge and a giant potassium peak in a corona-poled glass.

We visualized a region of a spatial electric charge in a corona-poled soda-lime glass using scanning electron microscopy (SEM). The SEM image obtained perfectly coincides with a numerically calculated distribution of the spatial charge in the structure. Compositional depth profiles of the glass were characterized with energy dispersive x-ray (EDX) analysis.

SERS-Active Pattern in Silver-Ion-Exchanged Glass Drawn by Infrared Nanosecond Laser.

The irradiation of silver-to-sodium ion-exchanged glass with 1.06-μm nanosecond laser pulses of mJ-range energy results in the formation of silver nanoparticles under the glass surface. Following chemical removal of ~25-nm glass layer reveals a pattern of nanoparticles capable of surface enhancement of Raman scattering (SERS).

Mechanism of Thermal Charge Relaxation in Poled Silicate Glasses in a Wide Temperature Range (From Liquid Nitrogen to Glass Melting Temperature).

Data on thermally stimulated depolarization current (TSDC) study of the same poled glass in the temperature range 100-1000 K are analyzed. Four specific temperature ranges in the TSDC spectrum of this glass are identified, with each range being attributed to the charge relaxation processes of different natures. During linear heating in the temperature range 100-250 K, charge relaxation is related to the adsorption/desorption of particles from the atmosphere, supposedly water cluster ions H(HO).

Nonresonant Local Fields Enhance Second-Harmonic Generation from Metal Nanoislands with Dielectric Cover.

We study second-harmonic generation from gold nanoislands covered with amorphous titanium oxide (TiO_{2}) films. As the TiO_{2} thickness increases, the plasmon resonance of the nanoislands shifts away from the second-harmonic wavelength of 532 nm, diminishing the resonant enhancement of the process at this wavelength. Nevertheless, the second-harmonic signal is enhanced by up to a factor of 45 with increasing TiO_{2} thickness.

Heat-sink free CW operation of injection microdisk lasers grown on Si substrate with emission wavelength beyond 1.3 μm.

High-performance injection microdisk (MD) lasers grown on Si substrate are demonstrated for the first time, to the best of our knowledge. Continuous-wave (CW) lasing in microlasers with diameters from 14 to 30 μm is achieved at room temperature. The minimal threshold current density of 600  A/cm (room temperature, CW regime, heatsink-free uncooled operation) is comparable to that of high-quality MD lasers on GaAs substrates.

Electrically pumped InGaAs/GaAs quantum well microdisk lasers directly grown on Si(100) with Ge/GaAs buffer.

In this work we report, to the best of our knowledge, the first quantum well electrically-pumped microdisk lasers monolithically deposited on (001)-oriented Si substrate. The III-V laser structure was epitaxially grown by MOCVD on silicon with an intermediate MBE-grown Ge buffer. Microlasers with an InGaAs/GaAs quantum well active region were tested at room temperature.

2D-patterning of self-assembled silver nanoisland films.

The paper is dedicated to the recently developed by the authors technique of silver nanoisland growth, allowing self-arrangement of 2D-patterns of nanoislands. The technique employs silver out-diffusion from ion-exchanged glass in the course of annealing in hydrogen. To modify the silver ion distribution in the exchanged soda-lime glass we included the thermal poling of the ion-exchanged glass with a profiled electrode as an intermediate stage of the process.

Mode selection in InAs quantum dot microdisk lasers using focused ion beam technique.

Optically pumped InAs quantum dot microdisk lasers with grooves etched on their surface by a focused ion beam are studied. It is shown that the radial grooves, depending on their length, suppress the lasing of specific radial modes of the microdisk. Total suppression of all radial modes, except for the fundamental radial one, is also demonstrated.

Revealing the nanoparticles aspect ratio in the glass-metal nanocomposites irradiated with femtosecond laser.

We studied a femtosecond laser shaping of silver nanoparticles embedded in soda-lime glass. Comparing experimental absorption spectra with the modeling based on Maxwell Garnett approximation modified for spheroidal inclusions, we obtained the mean aspect ratio of the re-shaped silver nanoparticles as a function of the laser fluence. We demonstrated that under our experimental conditions the spherical shape of silver nanoparticles changed to a prolate spheroid with the aspect ratio as high as 3.

Ultrasmall microdisk and microring lasers based on InAs/InGaAs/GaAs quantum dots.

Unlabelled: Ultrasmall microring and microdisk lasers with an asymmetric air/GaAs/Al0.98Ga0.02As waveguide and an active region based on InAs/InGaAs/GaAs quantum dots emitting around 1.

Erratum to: Plasmonic molecules via glass annealing in hydrogen.

[This corrects the article DOI: 10.1186/1556-276X-9-606.].

Plasmonic molecules via glass annealing in hydrogen.

Unlabelled: Growth of self-assembled metal nanoislands on the surface of silver ion-exchanged glasses via their thermal processing in hydrogen followed by out-diffusion of neutral silver is studied. The combination of thermal poling of the ion-exchanged glass with structured electrode and silver out-diffusion was used for simple formation of separated groups of several metal nanoislands presenting plasmonic molecules. The kinetics of nanoisland formation and temporal evolution of their size distribution on the surface of poled and unpoled glass are modeled.

Control of emission spectra in quantum dot microdisk/microring lasers.

Focused ion beam is applied to quantum dot based microresonators to form pits or groove on their surface. The emission spectra of the resonators based lasers are significantly thinned out after the ion beam milling, and one or two modes become dominant instead of a group of modes having comparable intensities. The linewidth of the lasing mode is kept unchanged, whereas the lasing threshold demonstrates an insignificant growth.