Stefano Schutzmann

High-energy angle resolved reflection spectroscopy on three-dimensional photonic crystals of self-organized polymeric nanospheres

We report on the optical characterization of three-dimensional opal-like photonic crystals made by self-organized nanospheres of poly[styrene-(co-2-hydroxyethyl methacrylate)] having a face centred cubic (fcc) structure oriented along the [111] direction. A detailed optical characterization of the samples is presented using angle resolved reflection spectroscopy in specular geometry. The investigated energies are between a/lambda=0.5 and a/lambda=1.5 (where a is the lattice parameter and lambda is the light wavelength), a region in which both first and second-order Bragg diffraction are expected. Some interesting features as branching of the Bragg peak dispersion and high energy reflection peaks are revealed. We compare the experimental data with theoretical calculations using both Bragg diffraction and band structure approach. A comparison with recent results reported in the literature is also presented.

1.3 μm light amplification in dye-doped hybrid sol-gel channel waveguides

We report on light amplification of dye-doped hybrid channel waveguides in the near-infrared region. Films have been grown both on glass and silicon substrates by a spin-coating process that uses a hybrid organic/inorganic sol-gel route. Doped films have been obtained by incorporation of an organic dye (IR1051) emitting in the 1.1–1.3 μm spectral region. Active channel waveguides have been synthesized by photolitographic and ion-milling techniques. An optical gain of about 11 cm−1 was estimated by amplified spontaneous emission measurements. An estimation of the optical losses of the hybrid waveguides is also reported.

Polymethine Dyes as Novel Efficient Infrared Electroluminescence Materials

We examined the electroluminescence (EL) characteristics of four polymethine dyes to evaluate both their advantages and limitations as infrared (IR) EL materials. The IR EL intensity showed a marked dependence on the IR dye, and an IR EL quantum efficiency of 3.6 × 10−2% photons/electron was measured for the most efficient IR EL dye, 2-[2-[2-chloro-3-[2-(1-dodecyl-1,2-dihydro-benzo[c,d]-indol-2-ylidene)-ethylidene]-1-cyclohexen-1-yl]-ethenyl]-1-dodecyl-benzo[c,d]indolium chloride (SO447). We discuss the IR EL characteristics of these dyes in terms of photoluminescence efficiency, competitive visible/near-IR EL and dimer EL, and trapping efficiency.

Toward optical and superconducting circuit integration

The physics of the interaction between coherent light and superconductivity is a very intriguing subject but the alignment of a laser beam with integrated superconducting systems (thin films, striplines or tunnel junctions) has represented so far a real bottleneck for the experimentalists. The integration of both junctions and waveguides on the same chip surely represents a possible path around this difficulty. In this paper we report on the combined integration of optical structures based on hybrid channel waveguides with superconducting Josephson junctions circuits. The optical films are grown on silicon substrates by a spin-coating process using the hybrid organic/inorganic sol–gel route. The channel waveguides are deposited on a buffer layer and realized by photolithographic and ion milling techniques. We find that the optical buffer is a good substrate for SIS Josephson junctions and circuitry based on the Nb/Al–AlOx/Nb trilayer processing. The junctions produced present good current–voltage characteristics with critical current density of the order of 1 kA cm−2, high subgap resistance and good uniformity. Our results show that the quality of the Josephson junctions is well preserved even when they are grown on the sol–gel buffer layer.

Planar polymeric multilayer structures for electro-optical applications

In this work we report on the preliminary results of compatibility, fabrication and characterization of two planar polymeric multilayer structures for electro-optic applications. The structures are composed by three polymeric layers grown on glass substrate. Buffer and cladding layers were synthesized using polymethylmethacrylate (PMMA). The guiding layers were composed by Polysulfone (PSU) and by a mixture of PMMA and polycarbonate (PC) both doped with Disperse Red 1 (DR1) molecules as nonlinear active units. Linear and nonlinear optical characterization of the structures by refractive index, absorption, optical losses, Second Harmonic Generation (SHG) and time stability measurements have been carried out.

Evidence of refractive index anisotropy in hybrid sol-gel slab waveguides deposited by spin-coating technique

In this work we report on hybrid organic/inorganic sol-gel based optical waveguides in slab configuration grown both on glass and silicon substrates by spin-coating process. The samples were obtained using Zr(IV)-propoxide as inorganic precursor and 3-glycidoxypropyltrimethoxisilane (GLYMO) as organic component in molar ratio of 3/1. Optical characterization of each layer has been accomplished performing refractive index measurements at different wavelengths in the visible and near infrared regions using an home-made experimental setup developed in our laboratory. Measurements have evidenced a difference between the in-plane and out-of-plane refractive index. We found that the amount of the optical anisotropy depends on the speed of spinning deposition and on the curing temperature. In particular the anisotropy increases with the increasing of speed deposition and with the increasing of curing temperature. Results were also confirmed by spectroscopic ellipsometric measurements. We attributed the optical anisotropy to a preferential orientation of the organic groups of the alkoxysilane precursor (GLYMO) during spin coating deposition.

Studies of temporal stability of poled nonlinear optical polymer films

Guest-host polymer system with potential use in electro-optic devices is discussed. The polymer host is a polyimide and the guest chromophore is Disperse Red 19 (DR 19). Decay times of poled order after corona poling procedure have been derived from the behaviour at elevated temperatures below glass transition temperature Tg using Arrhenius plots. An extrapolated lifetime greater than 30 years at room temperature has been obtained.