Observation of bright polariton solitons in a semiconductor microcavity

Microcavity polaritons are composite half-light half-matter quasi-particles, which have recently been demonstrated to exhibit rich physical properties, such as non-equilibrium Bose-Einstein condensation, parametric scattering and superfluidity. At the same time, polaritons have some important advantages over photons for information processing applications, since their excitonic component leads to weaker diffraction and stronger inter-particle interactions, implying, respectively, tighter localization and lower powers for nonlinear functionality. Here we present the first experimental observations of bright polariton solitons in a strongly coupled semiconductor microcavity. The polariton solitons are shown to be non-diffracting high density wavepackets, that are strongly localised in real space with a corresponding broad spectrum in momentum space. Unlike solitons known in other matter-wave systems such as Bose condensed ultracold atomic gases, they are non-equilibrium and rely on a balance between losses and external pumping. Microcavity polariton solitons are excited on picosecond timescales, and thus have significant benefits for ultrafast switching and transfer of information over their light only counterparts, semiconductor cavity lasers (VCSELs), which have only nanosecond response time

Advances in full field microscopy with table-top soft x-ray lasers

We describe recent advances in the demonstration of table-top full field microscopes that use soft x-ray lasers for illumination. We have achieved wavelength resolution and single shot exposure operation with a very compact 46.9 nm microscope based on a desk-top size capillary discharge laser. This {lambda}-46.9 nm microscope has been used to capture full field images of a variety of nanostructure systems and surfaces. In a separate development we have demonstrated a zone plate microscope that uses {lambda}=13.2 nm laser illumination to image absorption defects in an extreme ultraviolet lithography (EUVL) mask in the same geometry used in a 4x demagnification EUVL stepper. Characterization of the microscope’s transfer function shows it can resolve 55 nm half period patterns. With these capabilities, the {lambda}-13.2 nm microscope is well suited for evaluation of pattern and defect printability of EUVL masks for the 22 nm node

Personalizing Cancer Pain Therapy: Insights from the Rational Use of Analgesics (RUA) Group

Introduction: A previous Delphi survey from the Rational Use of Analgesics (RUA) project involving Italian palliative care specialists revealed some discrepancies between current guidelines and clinical practice with a lack of consensus on items regarding the use of strong opioids in treating cancer pain. Those results represented the basis for a new Delphi study addressing a better approach to pain treatment in patients with cancer. Methods: The study consisted of a two-round multidisciplinary Delphi study. Specialists rated their agreement with a set of 17 statements using a 5-point Likert scale (0 = totally disagree and 4 = totally agree). Consensus on a statement was achieved if the median consensus score (MCS) (expressed as value at which at least 50% of participants agreed) was at least 4 and the interquartile range (IQR) was 3–4. Results: This survey included input from 186 palliative care specialists representing all Italian territory. Consensus was reached on seven statements. More than 70% of participants agreed with the use of low dose of strong opioids in moderate pain treatment and valued transdermal route as an effective option when the oral route is not available. There was strong consensus on the importance of knowing opioid pharmacokinetics for therapy personalization and on identifying immediate-release opioids as key for tailoring therapy to patients’ needs. Limited agreement was reached on items regarding breakthrough pain and the management of opioid-induced bowel dysfunction. Conclusion: These findings may assist clinicians in applying clinical evidence to routine care settings and call for a reappraisal of current pain treatment recommendations with the final aim of optimizing the clinical use of strong opioids in patients with cancer

Nonlinear optics and saturation behavior of quantum dot samples under continuous wave driving

The nonlinear optical response of self-assembled quantum dots is relevant to the application of quantum dot based devices in nonlinear optics, all-optical switching, slow light and self-organization. Theoretical investigations are based on numerical simulations of a spatially and spectrally resolved rate equation model, which takes into account the strong coupling of the quantum dots to the carrier reservoir created by the wetting layer states. The complex dielectric susceptibility of the ground state is obtained. The saturation is shown to follow a behavior in between the one for a dominantly homogeneously and inhomogeneously broadened medium. Approaches to extract the nonlinear refractive index change by fringe shifts in a cavity or self-lensing are discussed. Experimental work on saturation characteristic of InGa/GaAs quantum dots close to the telecommunication O-band (1.24-1.28 mm) and of InAlAs/GaAlAs quantum dots at 780 nm is described and the first demonstration of the cw saturation of absorption in room temperature quantum dot samples is discussed in detail

Current fluctuations in polystyrene nano-compounds

The current fluctuations in a polystyrene matrix (PS) doped by gold nanoparticles (Au-NPs) and small conjugated molecules of 8-hydroxyquinoline (8HQ) have been characterized. The electrical properties of the PS composite allow using it as a responsive layer in non-volatile memory devices due to its switching capability between two well separated conducting states. The analysis of current fluctuations at fixed bias voltages showed the presence of two states in charge carrier transport regardless of the operating conducting state of the device. Moreover, noise spectra have been investigated in the low frequency region, allowing the estimation of charge relaxation times between current levels in the two memory states. The presence of these slow and large fluctuations can seriously affect the final electrical performances of this class of nanostructured memories

Green production of lead-free BZT-BCT thin films for applications in MEMS devices

This paper reports the production of Lead-free (1-x)(BaZr0.2Ti0.8O3)-x(Ba0.7Ca0.3O3) ferro/piezoelectric thin films by means of repeated chemical solution deposition routes. Two different kinds of precursor solutions were compared: i) a literature standard precursor solution involving the use of 2-methoxyethanol (2-MOE) which is a toxic and carcinogenic solvent and ii) a “greener” precursor solution based on 1-methoxy-2-propanol (PGME), a non-toxic and non-carcinogenic solvent. Morphology, crystal structure and ferroelectric behavior of the films is also reported

Static and dynamic properties of cavity solitons in VCSELs with optical injection

The static and dynamical properties of cavity solitons in a vertical cavity surface emitting laser with optical injection are investigated. Analytical results about the instabilities affecting the homogeneous steady state are presented. These instabilities play a key role in the determination of the necessary and favorable conditions for cavity soliton existence. Optimization of an all-optical delay line by tuning the injected field frequency leads to a five fold increase of the soliton velocity in the transverse plane. Finally, the phenomenon of cavity soliton merging is applied to combine input signals in optical information processing and to manipulate two dimensional optical memories

Printed functionalized capacitors for water-induced label-free detection of DNA hybridization

In the last decade, new device concepts based on novel fabrication methods have emerged as a powerful and general class of supersensitive sensors for the direct detection of biological and chemical targets. Pushed by the opportunity to activate the physical-chemical phenomena at the nanoscale, novel patterning paradigms have gained nanofabrication accuracy accompanied by the fast development of bottom-up strategies. In this frenetic framework, the combination of some heterogeneous techniques-basically nano-imprint lithography, grafting of functional molecules, and synthesis of new ligands and probes to capture specific biological targets-have gained strong attention as enabling emerging technological mixture to fabricate ultra dense array of specialized sensors. Within the scope of this technological convergence, the paper is basically devoted to describe the processes involved in the production of stamps for nanoimprint lithography, the fabrication of printed array of silicon sensors on the micrometer and sub-micrometer resolution, the subsequent covalent biofunctionalization with single strand DNA and some preliminary electrical detection of the hybridization events via water modulating ac resistance. Among the possible choices, focus was given to planar functionalized capacitors for their intrinsic simple configuration and also because they appeared to be the most promising candidates for mass production in printed device architecture. The paper is based on original results but contains also data and achievements taken from the literature to make the discussion self-contained. © 2011 American Scientific Publishers