Twin polaritons in semiconductor microcavities

The quantum correlations between the beams generated by polariton pair scattering in a semiconductor microcavity above the parametric oscillation threshold are computed analytically. The influence of various parameters like the cavity-exciton detuning, the intensity mismatch between the signal and idler beams and the amount of spurious noise is analyzed. We show that very strong quantum correlations between the signal and idler polaritons can be achieved. The quantum effects on the outgoing light fields are strongly reduced due to the large mismatch in the coupling of the signal and idler polaritons to the external photons

Mechanical testing ontology for digital-twins: A roadmap based on EMMO

The enormous amount of materials data currently generated by high throughput experiments and computations poses a significant challenge in terms of data integration and sharing. A common ontology lays the foundation for solving this issue, enabling semantic interoperability of models, experiments, software and data which is vital for a more rational and efficient development of novel materials. This paper is based on the current efforts by the European Materials Modelling Council (EMMC) on establishing common standards for materials through the European Materials & Modelling Ontology (EMMO) and demonstrates the application of EMMO to the mechanical testing field. The focus of this paper is to outline the approach to develop EMMO compliant domain ontologies

Atomic Carbon in Galaxies

We present new measurements of the ground state fine-structure line of atomic carbon at 492 GHz in a variety of nearby external galaxies, ranging from spiral to irregular, interacting and merging types. In comparison with CO(1-0), the CI(1-0) intensity stays fairly comparable in the different environments, with an average value of the ratio of the line integrated areas in Kkm/s of CI(1-0)/CO(1-0) = 0.2 +/- 0.2. However, some variations can be found within galaxies, or between galaxies. Relative to CO lines, CI(1-0) is weaker in galactic nuclei, but stronger in disks, particularly outside star forming regions. Also, in NGC 891, the CI(1-0) emission follows the dust continuum at 1.3mm extremely well along the full length of the major axis where molecular gas is more abundant than atomic gas. Atomic carbon therefore appears to be a good tracer of molecular gas in external galaxies, possibly more reliable than CO. Atomic carbon can contribute significantly to the thermal budget of interstellar gas. Cooling due to C and CO amounts typically to 2 x 10^{-5} of the FIR continuum or 5% of the CII line. However, C and CO cooling reaches 30% of the gas total, in Ultra Luminous InfraRed Galaxies, where CII is abnormally faint. Together with CII/FIR, the emissivity ratio CI(1-0)/FIR can be used as a measure of the non-ionizing UV radiation field in galaxies.Comment: 26 pages, 8 figure

Signatures of the Youngest Starbursts: Optically-thick Thermal Bremsstrahlung Radio Sources in Henize 2-10

VLA radio continuum imaging reveals compact (<8 pc) ~1 mJy radio sources in the central 5" starburst region of the blue compact galaxy Henize 2-10. We interpret these radio knots as extremely young, ultra-dense HII regions. We model their luminosities and spectral energy distributions, finding that they are consistent with unusually dense HII regions having electron densities, 1500 cm^-3 < n_e < 5000 cm^-3, and sizes of 3-8 pc. Since these H II regions are not visible in optical images, we propose that the radio data preferentially reveal the youngest, densest, and most highly obscured starforming events. Energy considerations imply that each of the five \HII regions contains ~750 O7V equivalent stars, greater than the number found in 30 Doradus in the LMC. The high densities imply an over-pressure compared to the typical interstellar medium so that such objects must be short-lived (<0.5 Myr expansion timescales). We conclude that the radio continuum maps reveal the very young (<0.5 Myr) precursors of ``super starclusters'' or ``proto globular clusters'' which are prominent at optical and UV wavelengths in He 2-10. If the ultra-dense HII regions are typical of those which we predict will be found in other starbursting systems, then super starclusters spend 15% of their lifetime in heavily-obscured environments, similar to Galactic ultra-compact HII regions. This body of work leads us to propose that massive extragalactic star clusters (i.e. proto globular clusters) with ages <10^6 yr may be most easily identified by finding compact radio sources with optically-thick thermal bremsstrahlung spectral signatures.Comment: AASTeX, 8 figures 2 included with psfig in text; other 6 in jpeg format; Postscript versions of figures may be found at http://zem.ucolick.org/chip/Research/young_clusters.html -- Accepted for publication in the Astrophysical Journa

Engineering the spatial confinement of exciton-polaritons in semiconductors

We demonstrate the spatial confinement of electronic excitations in a solid state system, within novel artificial structures that can be designed having arbitrary dimensionality and shape. The excitations under study are exciton-polaritons in a planar semiconductor microcavity. They are confined within a micron-sized region through lateral trapping of their photon component. Striking signatures of confined states of lower and upper polaritons are found in angle-resolved light emission spectra, where a discrete energy spectrum and broad angular patterns are present. A theoretical model supports unambiguously our observations

Photodynamic therapy as adjuvant therapy in surgically treated pleural malignancies.

Five patients with a pleural malignancy (four malignant mesotheliomas and one localized low grade carcinoid) were treated with maximal surgical resection of the tumour followed by intraoperative adjuvant photodynamic therapy (PDT). The additional photodynamic treatment was performed with light of 652 nm from a high power diode laser, and meta-tetrahydroxy phenylchlorin as the photosensitizer. The light delivery to the thoracic cavity was monitored by in situ isotropic light detectors. The position of the light delivery fibre was adjusted to achieve optimal light distribution, taking account of reflected and scattered light in this hollow cavity. There was no 30-day post-operative mortality and only one patient suffered from a major complication (diaphragmatic rupture and haematopericardium). The operation time was increased by a maximum of 1 h to illuminate the total hemithoracic surface with 10 J cm(-2) (incident and scattered light). The effect of the adjuvant PDT was monitored by examination of biopsies taken 24 h after surgery under thoracoscopic guidance. Significant damage, including necrosis, was observed in the marker lesions with remaining malignancy compared with normal tissue samples, which showed only an infiltration with PMN cells and oedema of the striated muscles cells. Of the five patients treated, four are alive with no signs of recurrent tumour with a follow-up of 9-11 months. One patient was diagnosed as having a tumour dissemination in the skin around the thoracoscopy scar and died of abdominal tumour spread. Light delivery to large surfaces for adjuvant PDT is feasible in a relatively short period of time (< 1 h). In situ dosimetry ensures optimal light distribution and allows total doses (incident plus scattered light) to be monitored at different positions within the cavity. This combination of light delivery and dosimetry is well suited for adjuvant treatment with PDT in malignant pleural tumours