Single Molecule Activation and Computing (FOCUS)

The present project, FOCUS, will build a novel generation of biologically inspired molecular devices (MDs) based on the developments of new photonic tools. These photonic tools will use Plasmon Polariton and two-photon technology, enabling focused light spots with a diameter around 10 nm. FOCUS will also develop new light sensitive molecules that will be selectively activated by our new photonic tools. These new technological innovations will provide a way to control activation of single light sensitive molecules and will allow the investigation of molecular computation in a biological environment and with an unprecedented resolution. On the basis of these investigations and by using the developed new tools, FOCUS will design and test new MDs for amplification and information processing. FOCUS will: i - provide new photonic devices to control single molecules; ii – lay out the basis for understanding molecular computation in biological systems; iii - provide proofs of concept and suggestions for designing new molecular artificial computing systems; iv- build prototypes of these new MDs. FOCUS has formed a highly interdisciplinary consortium composed of nanotechnologists able to fabricate the new photonic devices - i.e. Enzo Di Fabrizio (IIT), Alpan Bek (METU) and Marco Lazzarino (CBM), chemists able to develop the photoswitches and assemble the MDs – i.e. Pau Gorostiza (IBEC) and Ljiljana Fruk (KIT) and biologists able to understand molecular mechanisms – i.e. Vincent Torre (SISSA) and Fabio Benfenati (IIT). The two companies RappOptoElectronic and NT-MDT Europe BV will transform the new tools and devices into marketable products.EU, Funded under :FP7-ICT-2009-

Low loss optical waveguides and polarization splitters with oxidized AlxGa1-xAs layers

Ankara : Department of Physics and the Institute of Engineering and Science of Bilkent University, 1998.Thesis (Master's) -- Bilkent University, 1998.Includes bibliographical references leaves 90-94.Low propagation loss waveguides, operating at 1.55 fim optical wavelength, are fabricated utilizing oxidized AhGai_a;As layers. MBE grown multilayer semiconductor heterostructures are characterized before and after oxidation by ellipsometric techniques. In fabrication of optical waveguides, reactive ion etching method is used extensively. Loss measurements are performed, involving a fiber input-coupled laser source setup using Fabry-Perot resonance technique. Propagation loss of an AlGaAs based multilayer rib waveguide with oxidized AhG ai_3,As top layer is observed to reduce from 6 dB/cm to as low as 1 clB/cm lor TM and from 3.7 dB/cm to as low as 0.6 dB/cm for TE polarizations in the presence of metal electrodes on top of the rib. These results arc compared with loss measurements on standard rib waveguides. Polarization splitters are also fabricated with the same material. Effect of the oxide layer on the polarization splitter’s coupling length for TE and TM polarizations are measured. Polarization extinction ratios as high as 12.4 dB are obtained. Polarization extinction ratios are also attempted to be controlled by the use of electro-optic effect in Al.x,.Gai_a;As system. Only AC fields are found to be effective.Bek, AlpanM.S

Engineering nonlinear response of nanomaterials using Fano resonances

We show that, nonlinear optical processes of nanoparticles can be controlled by the presence of interactions with a molecule or a quantum dot. By choosing the appropriate level spacing for the quantum emitter, one can either suppress or enhance the nonlinear frequency conversion. We reveal the underlying mechanism for this effect, which is already observed in recent experiments: (i) Suppression occurs simply because transparency induced by Fano resonance does not allow an excitation at the converted frequency. (ii) Enhancement emerges since nonlinear process can be brought to resonance. Path interference effect cancels the nonresonant frequency terms. We demonstrate the underlying physics using a simplified model, and we show that the predictions of the model are in good agreement with the 3-dimensional boundary element method (MNPBEM toolbox) simulations. Here, we consider the second harmonic generation in a plasmonic converter as an example to demonstrate the control mechanism. The phenomenon is the semi-classical analog of nonlinearity enhancement via electromagnetically induced transparency.Comment: 10 pages, 6 figure

Microcavity effects in the photoluminescence of hydrogenated amorphous silicon nitride

Fabry-Perot microcavities are used for the alteration of photoluminescence in hydrogenated amorphous silicon nitride grown with and without ammonia. The photoluminescence is red-near-infrared for the samples grown without ammonia, and blue-green far the samples grown with ammonia. In the Fabry-Perot microcavities, the amplitude of the photoluminescence is enhanced, while its linewidth is reduced with respect to the bulk hydrogenated amorphous silicon nitride. The microcavity was realized by a metallic back mirror and a hydrogenated amorphous silicon nitride - air or a metallic front mirror. The transmittance, reflectance, and absorbance spectra were also measured and calculated. The calculated spectra agree well with the experimental spectra. The hydrogenated amorphous silicon nitride microcavity has potential for becoming a versatile silicon based optoelectronic device such as a colot flat panel display, a resonant cavity enhanced light emitting diode, or a laser

Fano Enhancement of Unlocalized Nonlinear Optical Processes

Field localization boosts nonlinear optical processes at the hot spots of metal nanostructures. Fano resonances can further enhance these "local" processes taking place at the hot spots. However, in conventional nonlinear materials, the frequency conversion takes place along the entire crystal body. That is, the conversion process is "unlocalized". The path interference (Fano resonance) schemes developed for localized processes become useless in such materials. Here, we develop Fano enhancement schemes for unlocalized nonlinear optical processes. We show that 3 orders of magnitude Fano enhancement multiply the enhancements achieved via field trapping techniques, e.g., in epsilon-near-zero~(ENZ) materials. We demonstrate the phenomenon both analytically and by numerical solutions of Maxwell's equations. The match between the two solutions is impressive. We observe that the interference scheme for unlocalized processes is richer than the one for the local processes. The method can be employed for any kind of nonlinear optical conversion. Moreover, the Fano enhancement can be continuously controlled by an applied voltage.Comment: 10 pages, 5 figure

Visible photoluminescence from planar amorphous silicon nitride microcavities

Fabry-Perot microcavities were used for the enhancement and inhibition of photoluminescence (PL) in a hydrogenated amorphous silicon nitride (a-SiNx:H) microcavity fabricated with and without ammonia. A planar microcavity was realized that included a metallic back mirror and an a-SiNx:H-air or a metallic front mirror. The PL extends from the red part of the spectrum to the near infrared for the samples grown without ammonia. The PL is in the blue-green part of the spectrum for the samples grown with ammonia. The PL amplitude is enhanced and the PL linewidth is reduced with respect to those in bulk a-SiNx:H. The numerically calculated transmittance, reflectance, and absorbance spectra agree well with the experimentally measured spectra. (C) 1998 Optical Society of America [S0740-3224(98)00211-2] OCIS codes: 230.5750, 250.5230, 310.0310