36 research outputs found
Circular dielectric cavity and its deformations
The construction of perturbation series for slightly deformed dielectric
circular cavity is discussed in details. The obtained formulae are checked on
the example of cut disks. A good agreement is found with direct numerical
simulations and far-field experiments.Comment: 17 pages, 12 figure
Gain properties of dye-doped polymer thin films
Hybrid pumping appears as a promising compromise in order to reach the much
coveted goal of an electrically pumped organic laser. In such configuration the
organic material is optically pumped by an electrically pumped inorganic device
on chip. This engineering solution requires therefore an optimization of the
organic gain medium under optical pumping. Here, we report a detailed study of
the gain features of dye-doped polymer thin films. In particular we introduce
the gain efficiency , in order to facilitate comparison between different
materials and experimental conditions. The gain efficiency was measured with
various setups (pump-probe amplification, variable stripe length method, laser
thresholds) in order to study several factors which modify the actual gain of a
layer, namely the confinement factor, the pump polarization, the molecular
anisotropy, and the re-absorption. For instance, for a 600 nm thick 5 wt\% DCM
doped PMMA layer, the different experimental approaches give a consistent value
80 cm.MW. On the contrary, the usual model predicting the gain
from the characteristics of the material leads to an overestimation by two
orders of magnitude, which raises a serious problem in the design of actual
devices. In this context, we demonstrate the feasibility to infer the gain
efficiency from the laser threshold of well-calibrated devices. Besides,
temporal measurements at the picosecond scale were carried out to support the
analysis.Comment: 15 pages, 17 figure
Inferring periodic orbits from spectra of simple shaped micro-lasers
Dielectric micro-cavities are widely used as laser resonators and
characterizations of their spectra are of interest for various applications. We
experimentally investigate micro-lasers of simple shapes (Fabry-Perot, square,
pentagon, and disk). Their lasing spectra consist mainly of almost equidistant
peaks and the distance between peaks reveals the length of a quantized periodic
orbit. To measure this length with a good precision, it is necessary to take
into account different sources of refractive index dispersion. Our experimental
and numerical results agree with the superscar model describing the formation
of long-lived states in polygonal cavities. The limitations of the
two-dimensional approximation are briefly discussed in connection with
micro-disks.Comment: 13 pages, 19 figures, accepted for publication in Physical Review
Trace formula for dielectric cavities II: Regular, pseudo-integrable, and chaotic examples
Dielectric resonators are open systems particularly interesting due to their
wide range of applications in optics and photonics. In a recent paper [PRE,
vol. 78, 056202 (2008)] the trace formula for both the smooth and the
oscillating parts of the resonance density was proposed and checked for the
circular cavity. The present paper deals with numerous shapes which would be
integrable (square, rectangle, and ellipse), pseudo-integrable (pentagon) and
chaotic (stadium), if the cavities were closed (billiard case). A good
agreement is found between the theoretical predictions, the numerical
simulations, and experiments based on organic micro-lasers.Comment: 18 pages, 32 figure
Bilan génétique des programmes de conservation des races ovines Solognote et Mérinos précoce
Bilan génétique des programmes de conservation des races ovines Solognote et Mérinos précoce
International audienc
A comparative study of gemcitabine/doxorubicin and cyclophosphamide/doxorubicin combinations in first-line metastatic breast cancer
Computational and experimental studies on the efficiency of Rosmarinus officinalis polyphenols as green corrosion inhibitors for XC48 steel in acidic medium
The performances of the extract obtained from Rosmarinus officinalis (RO) on the corrosion inhibition of XC48 steel is examined by mass loss method, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), potentiodynamic polarization (PDP), Fourier transform infrared (FTIR) spectroscopy and liquid chromatography–mass spectrometry (LC–MS). Investigations are performed in hydrochloric acid solution at 1 M concentration at different temperatures. Results show that the RO extract behaves as an inhibitor of mixed-type; in particular, the inhibition efficiency is augmented at greater concentration of the inhibitor and decreases with the rise of the temperature from 303 K to 333 K. The values of activation and free energy of inhibition reaction support the hypothesis of a mechanism of physisorption that is adequately described by the Langmuir equilibrium model. The retrieved outcomes are confirmed by SEM observations, which reveal that the adsorbed inhibitor molecules completely hinder the HCl attacks at the steel grain boundaries. Finally, quantum chemical calculations show that among the most abundant component detected in the RO extract, carnosic acid has a greater inhibitor potential with respect to carnosol