Fabrication of spectrally sharp Si-based dielectric resonators: combining etaloning with Mie resonances.

We use low-resolution optical lithography joined with solid state dewetting of crystalline, ultra-thin silicon on insulator (c-UT-SOI) to form monocrystalline, atomically smooth, silicon-based Mie resonators in well-controlled large periodic arrays. The dewetted islands have a typical size in the 100 nm range, about one order of magnitude smaller than the etching resolution. Exploiting a 2 µm thick SiO2 layer separating the islands and the underlying bulk silicon wafer, we combine the resonant modes of the antennas with the etalon effect. This approach sets the resonance spectral position and improves the structural colorization and the contrast between scattering maxima and minima of individual resonant antennas. Our results demonstrate that templated dewetting enables the formation of defect-free, faceted islands that are much smaller than the nominal etching resolution and that an appropriate engineering of the substrate improves their scattering properties. These results are relevant to applications in spectral filtering, structural color and beam steering with all-dielectric photonic devices.

Tailoring Correlations of the Local Density of States in Disordered Photonic Materials.

We present experimental evidence for the different mechanisms driving the fluctuations of the local density of states (LDOS) in disordered photonic systems. We establish a clear link between the microscopic structure of the material and the frequency correlation function of LDOS accessed by a near-field hyperspectral imaging technique. We show, in particular, that short- and long-range frequency correlations of LDOS are controlled by different physical processes (multiple or single scattering processes, respectively) that can be-to some extent-manipulated independently. We also demonstrate that the single scattering contribution to LDOS fluctuations is sensitive to subwavelength features of the material and, in particular, to the correlation length of its dielectric function. Our work paves a way towards complete control of statistical properties of disordered photonic systems, allowing for designing materials with predefined correlations of LDOS.

Mapping local charge recombination heterogeneity by multidimensional nanospectroscopic imaging.

As materials functionality becomes more dependent on local physical and electronic properties, the importance of optically probing matter with true nanoscale spatial resolution has increased. In this work, we mapped the influence of local trap states within individual nanowires on carrier recombination with deeply subwavelength resolution. This is achieved using multidimensional nanospectroscopic imaging based on a nano-optical device. Placed at the end of a scan probe, the device delivers optimal near-field properties, including highly efficient far-field to near-field coupling, ultralarge field enhancement, nearly background-free imaging, independence from sample requirements, and broadband operation. We performed ~40-nanometer-resolution hyperspectral imaging of indium phosphide nanowires via excitation and collection through the probes, revealing optoelectronic structure along individual nanowires that is not accessible with other methods.

Young's type interference for probing the mode symmetry in photonic structures.

A revisited realization of the Young's double slit experiment is introduced to directly probe the photonic mode symmetry by photoluminescence experiments. We experimentally measure the far field angular emission pattern of quantum dots embedded in photonic molecules. The experimental data well agree with predictions from Young's interference and numerical simulations. Moreover, the vectorial nature of photonic eigenmodes results in a rather complicated parity property for different polarizations, a feature which has no counterpart in quantum mechanics.

Anderson localization of near-visible light in two dimensions.

We report on the observation of Anderson localization of near-visible light in two-dimensional systems. Our structures consist of planar waveguides in which disorder is introduced by randomly placing pores with controlled diameter and density. We show how to design structures in which localization can be observed and describe both the realization of the materials and the actual observation of Anderson localized modes by near-field scanning microscopy.

Near-field short range correlation in optical waves transmitted through random media.

Two-dimensional near-field images of light transmitted through a disordered dielectric structure have been measured for two probe wavelengths. From these data, the 2D spatial dependence of the intensity correlation function, C(deltaR-->), has been extracted. We observe that the spatial dependence of C is dominated by a rapidly varying feature determined by the wavelength of the probe light and the average refractive index of the material, as expected by theory. Finally, we deduce the absolute value of the effective refractive index by fitting the theoretical spatial dependence of C to our experimental results.

Near-field measurement of short-range correlation in optical waves transmitted through random media.

Two-dimensional near-field images of speckle patterns formed by optical waves transmitted through a disordered porous silica glass sample are measured. The corresponding 2D intensity correlation function, C, is extracted. The subwavelength spatial resolution of near-field microscopy allows us to resolve in the spatial distribution of C the expected subwavelength oscillations and to follow their dependence on the excitation wavelength. Finally, we deduce the effective refractive index of the material by fitting the theoretical spatial dependence of C to our experimental results.

Quantum mechanical repulsion of exciton levels in a disordered quantum well.

Spatially resolved photoluminescence spectra of a single quantum well are recorded by near-field spectroscopy. A set of over four hundred spectra displaying sharp emission lines from localized excitons is subject to a statistical analysis of the two-energy autocorrelation function. An accurate comparison with a quantum theory of the exciton center-of-mass motion in a two-dimensional spatially correlated disordered potential reveals clear signatures of quantum mechanical energy level repulsion, giving the spatial and energetic correlations of excitons in disordered quantum systems.

Low temperature near-field luminescence studies of localized and delocalized excitons in quantum wires.

Excitons in a GaAs quantum wire were studied in high-resolution photoluminescence experiments performed at a temperature of about 10 K with a spatial resolution of 160 nm and a spectral resolution of 100 microeV. We report the observation of quasi-one-dimensional excitons which are delocalized over a length of up to several micrometres along the quantum wire. Such excitons give rise to a 10 meV broad luminescence band, representing a superposition of transitions between different delocalized states. In addition, we find a set of sharp luminescence peaks from excitons localized on a sub150 nm length scale. Theoretical calculations of exciton states in a disordered quasi-one-dimensional potential reproduce the experimental results.

Zinc and copper metabolism during open-heart surgery.

Zinc and copper changes were studied in plasma, whole blood, urine and myocardium in 15 patients undergoing valve replacement in hypothermic cardiopulmonary bypass with hemodilution. During the cardiopulmonary bypass, a fall in plasma copper and zinc concentration was related to hemodilution. The zinc concentration also decreased in whole blood, but remained unchanged intracellularly. The urinary concentration of both cations, but not the output, decreased at the end of the operation in relation to the baseline values. The myocardial copper and zinc concentrations increased during the aortic cross-clamping period. The possible causes and significance of these changes are considered.

Surgical approach to renal cell carcinoma extending into the right atrium through the inferior vena cava.

Successful management of a patient with an intracardiac tumor thrombus of renal carcinoma is described. This case and a few others in the literature have led us to consider the clinical signs of cavo-atrial obstruction, frequently silent and unspecific; the diagnostic methodology, especially based upon CAT scan and cavography, and the type of surgery and surgical technique called for, especially as regards the approach and the possible use of extracorporeal circulation (ECC).

[Cavoauricular thrombectomy under extracorporeal circulation and right superior lobectomy for paraneoplastic thrombosis in a case of lung cancer]. / Thrombectomie cavo-auriculaire en C.E.C. et lobectomie supérieure droite pour thrombose paraneoplasique dans un cas de cancer du poumon.

A patient with superior vena cava thrombosis from cancer of the right lung is described. The particular interest of this case resides in: The numerical scantiness of cases reported in the literature: 12 cases reviewed; The exceptional nature of the etiopathogenic mechanism: paraneoplastic thrombosis; and the more precise problems relating to the indication, technique and tactics with respect to surgery.

Congenital quadricuspid aortic valve with displacement of the right coronary orifice.

To date only five patients have undergone surgery for severe incompetence due to quadricuspid aortic valve (5-9). This report describes a new case of congenital quadricuspid aortic valve with severe regurgitation and associated displacement of the right coronary orifice, in which the abnormal valve was excised and replaced by a Björk-Shiley tilting disc valve prosthesis.

Ultrafiltration during open-heart surgery in chronic renal failure.

Ultrafiltration at the end of cardiopulmonary bypass is an important improvement in major cardiac surgery in patients with chronic renal failure and also in dialysis-dependent patients. It has many advantages over pre- and postoperative haemodialysis or peritoneal dialysis. The method, employing disposable equipment, is easy to use, does not prolong total pump time, as it is of short duration, and restores at the end of operation normovolaemia and haematocrit values.

[Cardiac electrostimulation in childhood (author's transl)]. / La elettrostimolazione in età pediatrica. Su due casi richiedenti impianto di pacemaker.

The AA. relate on two cases of pacemaker implantation in childhood, and they outline the causes that make necessary a cardiac pacemaker in such an age and the troubles can possibly occur.