Low Loss Metamaterials Based on Classical Electromagnetically Induced Transparency

We demonstrate theoretically that electromagnetically induced transparency can be achieved in metamaterials, in which electromagnetic radiation is interacting resonantly with mesoscopic oscillators rather than with atoms. We describe novel metamaterial designs that can support full dark resonant state upon interaction with an electromagnetic beam and we present results of its frequency-dependent effective permeability and permittivity. These results, showing a transparency window with extremely low absorption and strong dispersion, are confirmed by accurate simulations of the electromagnetic field propagation in the metamaterial

Absolute radiant power measurement for the Au M lines of laser-plasma using a calibrated broadband soft X-ray spectrometer with flat-spectral response

International audienceCEA implemented an absolutely calibrated broadband soft X-ray spectrometer called DMX on the Omega laser facility at the Laboratory for Laser Energetics (LLE) in 1999 to measure radiant power and spectral distribution of the radiation of the Au plasma. The DMX spectrometer is composed of 20 channels covering the spectral range from 50 eV to 20 keV. The channels for energies below 1.5 keV combine a mirror and a filter with a coaxial photo-emissive detector. For the channels above 5 keV the photoemissive detector is replaced by a conductive detector. The intermediate energy channels (1.5 keV < photon energy < 5 keV) use only a filter and a coaxial detector. A further improvement of DMX consists in flat-response X-ray channels for a precise absolute measurement of the photon flux in the photon energy range from 0.1 keV to 6 keV. Such channels are equipped with a filter, a Multilayer Mirror (MLM), and a coaxial detector. We present as an example the development of channel for the gold M emission lines in the photon energy range from 2 keV to 4 keV which has been successfully used on the OMEGA laser facility. The results of the radiant power measurements with the new MLM channel and with the usual channel composed of a thin titanium filter and a coaxial detector (without mirror) are compared. All elements of the channel have been calibrated in the laboratory of the Physikalisch-Technische Bundesanstalt, Germany's National Metrology Institute, at the synchrotron radiation facility BESSY II in Berlin using dedicated well established and validated methods

Performance evaluation of multi-band OFDM systems for short-haul optical communications

Performance evaluation of ultra-wide band radio signals based on multi-band (MB) orthogonal frequency division multiplexing (OFDM) system is presented. These systems are very attractive due to their capability to deliver high-speed data streams, their co-existence with the current radio standards and their suitability for transmission in fibre. In this paper, the work is focused on the simulation of both single-input-single-out (SISO) and multiple-input-multiple-output (MIMO) OFDM configuration with transmission over an optical channel model. Different system parameters and transmission strategies are analyzed to estimate the bit-error rate (BER) and packet-error-ratio (PER) performance

Observation and modeling of long-wavelength InAs/InP (100) quantum dot amplifier small signal gain spectra

Measured gain spectra from InAs/InP (100) quantum-dot amplifiers have been analyzed with a quantum-dot rate-equation model. The amplifiers are fabricated to have a peak gain wavelength around 1700nm. Our comparison between measured and simulated gain spectra shows that two effects in the quantum-dot material introduce the 65 nm blue shift and change in shape that have been observed in the measured gain spectrum with an increase in injection current density from 1000A/cm2 to 3000A/cm2. The first effect is the shift from GS to ES, and the second effect the dot size dependent filling due to the dot size dependent escape rates

Simulations of fast switching between longitudinal modes of semiconductor laser cavity induced by on-chip filtered optical feedback

A set of delay differential equations is introduced to describe the multimode dynamics of a DBR laser cavity integrated with a passive filtered-feedback cavity. We demonstrate that a modulation of the central frequency of the feedback filter can be used to induce switches between different lasing modes of the DBR laser. The dependence on different model parameters such as feedback strength, feedback phase or cavity losses is quantitatively investigated

Deeply-etched DBR gratings for photonics integrated circuits and tunable lasers

Deeply-etched DBR gratings are versatile components for application in Photonic Integrated Circuits. A fabrication technology was developed that allows integration of deeply-etched DBR mirrors with other active and passive components on an InP chip. As a demonstration of the many applications of the DBR mirrors a novel discretely tunable laser based on filtered feedback is presented. The laser has a simple tuning method and the potentially sub-ns switching speed makes the device promising for packet-switching applications. Because of the simple control scheme, the device also has potential for low-cost applications like metro- and access networks

Quantum dot twin stripe lasers as emitter and receiver in chaotic encrypted communication systems

The complex nonlinear and chaotic regimes observed in laterally coupled diode lasers – or twin stripe lasers– make this device a real contender for the emitter and receiver in chaotic encrypted communication systems, since the chaos is produced on chip and no other elements have to be added to the set-up. The main problem until now was to be able to synchronize two of those devices, due to the difficulty of fabricating a pair similar enough. Our approach is to use Quantum Dots for the active region of the twin stripes, which allows for the use of shallow etching to electrically isolate both stripes due to the zero dimensional confinement of the Quantum Dots. In this paper we present the first time that a pair of twin stripe lasers has been synchronized together with an observation of transitions to chaos such as those found in single-stripe lasers subject to external influences

Refractive index sensing with an InGaAsP photonic crystal membrane cavity by means of photoluminescence

We report the experimental investigation of several types of InGaAsP photonic crystal membrane cavities with embedded InAs quantum dots for use as refractive index sensors. The cavities are read out by photoluminescence, avoiding the need to couple them to waveguides. The sensitivities are determined from infiltration of the cavities with sugar-water solutions with known refractive index. The sensitivities increase markedly when the resonance frequency approaches the air band and correlate inversely with the quality factor. A maximum sensitivity of 425 nm per refractive index unit is found, a value among the highest reported so far. Preliminary surface functionalization for use as a biosensor is also reported

Monoamine oxidase inhibitors allow locomotor and rewarding responses to nicotine.

Although nicotine is generally considered to be the main compound responsible for the addictive properties of tobacco, experimental data indicate that nicotine does not exhibit all the characteristics of other abused substances, such as psychostimulants and opiates. For example, nicotine is only a weak locomotor enhancer in rats and generally fails to induce a locomotor response in mice. This observation contradicts the general consensus that all drugs of abuse release dopamine in the nucleus accumbens, a subcortical structure, and thus increase locomotor activity in rodents. Because tobacco smoke contains monoamine oxidase inhibitors (MAOIs) and decreases MAO activity in smokers, we have combined MAOIs with nicotine to determine whether it is possible to obtain a locomotor response to nicotine in C57Bl6 mice. Among 15 individual or combined MAOIs, including harmane, norharmane, moclobemide, selegiline, pargyline, clorgyline, tranylcypromine and phenelzine, only irreversible inhibitors of both MAO-A and -B (tranylcypromine, phenelzine, and clorgyline+selegiline) allowed a locomotor response to nicotine. The locomotor stimulant interaction of tranylcypromine and nicotine was absent in beta2-nicotinic acetylcholine receptor subunit knockout mice. Finally, it was found that, whereas na? rats did not readily self-administer nicotine (10 microg/kg/injection), a robust self-administration of nicotine occurred when animals were pretreated with tranylcypromine (3 mg/kg). Our data suggest that MAOIs contained in tobacco and tobacco smoke act in synergy with nicotine to enhance its rewarding effects