Emile J. Knystautas

Fabrication and characterization of integrated optical waveguides in sulfide chalcogenide glasses

This paper reports on the fabrication process of As-S-(Se)-based chalcogenide glass optical waveguides using three techniques: photolithography, laser beam writing, and ion implantation. The fabrication method of the bulk sulfide glasses and the processing of integrated devices are described and assessed in light of the propagation characteristics and optical losses in each case.

High photoluminescence in erbium-doped chalcogenide thin films

Abstract The spectral properties of the chalcogenide glasses As2S3 and As24S38Se38-doped with Er3+ are presented and discussed. Thin films were formed by thermal evaporation and the erbium doping was obtained by subsequent ion implantation. Strong Er3+ emission at 1.54 μm has been observed. The high refractive index of these chalcogenide glasses lead to Er3+ emission cross-sections (15×10 −21 cm 2 ) which are two times higher than for doped silica glass. The lifetime of the Er3+ metastable 4I13/2 energy level was measured to be 2.3 ms. This short lifetime is consistent with the high emission cross-section. Furthermore, the very low phonon energies of chalcogenide glasses lead to relatively long lifetimes of the Er3+ 4I11/2 pump level, which have been measured to be of the order of 0.25 ms. These spectral properties make this glass a good candidate for applications in the field of integrated optics.

Non-linear glasses by metal cluster formation: synthesis and properties

Abstract Light waveguides were obtained by Na + + ion-exchange in a commercial soda-lime glass of composition (wt%): 71.9 SiO 2 , 1.9 Al 2 O 3 , 6.8 CaO, 1.1 K 2 O, 4.4 MgO, 13.5 Na 2 O, 0.4 SO 3 , with small contaminations of iron (15 ppm) and arsenic (300 ppm). Glass samples were immersed for 30 min in a molten salt bath of molar concentration 0.1 % AgNO 3 in NaNO 3 at 320 °C. Ion-exchanged samples were irradiated with helium, lithium and neon ions at an energy of 100 keV, with fluences in the 1×10 16 –1×10 17 ions/cm 2 range and current densities between 1 and 8 μA/cm 2 . The effect of the substrate temperature (room temperature, 90, 150 and 250 °C) was investigated. The formation of nanometer-size silver precipitates was observed, after irradiation, depending on the treatment conditions. The results were interpreted on the basis of the diffusivity of silver at the different temperatures and of the values of the energy deposited by the ion beams in electronic (ionization) processes and elastic collisions. Preliminary measurements of the third-order contribution to the electrical susceptibility indicate that the obtained materials exhibit optical non-linear properties which are interesting for the fabrication of optoelectronic devices.

Ion implantation, a method for fabricating light guides in polymers

Li+ and N+ ions were implanted into aliphatic polymethylmethacrylate (PMMA), polyvinylalcohol (PVA), and aromatic polyimide (PI) polycarbonate (PC) polymers in the energy range of 100–130 keV. Planar optical waveguides guiding between one and three modes were formed. For low implantation doses (≤ 1014 ions/cm2), total waveguide loss values at λ=633 nm were found to be less than 2 dB/cm. The changes in the refractive index were found to be very large (Δn≥0.05) in the case of PMMA and PVA. We interpret this change in refractive index as being due to the formation of aromatic compounds in the regions of electronic scattering.

Measurements of the diffusion rate of lithium in aluminum at low temperature by elastic recoil detection analysis

The diffusion coefficient of lithium in aluminum has been investigated as a function of temperature between 150 and 240 °C by elastic recoil detection analysis. This dependence is found to be well described by the following expression: D =0.37(+1.30−0.28)exp{−[(126.1 ±5.2)kJ/ mol/RT]} cm2/s.

POLYMER WAVEGUIDES UNDER ION IMPLANTATION : OPTICAL AND CHEMICAL ASPECTS

The effects of ion implantation on the linear and nonlinear optical properties of polymer thin films are studied. In the first step, good quality planar waveguides were made in a well known photoconducting polymer, polyvinylcarbazole (PVK), which has no intrinsic nonlinear optical properties. The polymer is deposited by spin-coating onto a BK7 glass substrate. A diffraction grating, etched on the substrate surface, acts as an input coupler for the waveguide. We present our results from the study of these polymer waveguides, following exposure to an energetic ion beam. The grating coupler method was used to characterize the linear and nonlinear optical properties of the waveguides before and after ion implantation. Due to the conjugated chains created by the implantation, we expect χ(3) type nonlinear properties and more specifically, an electronic nonlinear refractive index. The implanted polymer films are characterized by infrared and UV/visible spectroscopy to study structural modifications. The new structures created and the significant damage caused by the implantation are discussed.

Adsorption study of environmentally relevant concentrations of chlortetracycline on pinewood biochar.

The presence of pharmaceutically active compounds (PhACs) in water and wastewater has raised concerns because of potential environmental impacts and thus their removal is of high importance. The adsorption behavior of chlortetracycline (CTC) from aqueous solution on raw and activated pinewood biochar was studied at 298 K. The effect of initial pH of the solution was studied by performing the experiment at three different pHs (1, 5 and 9). At each pH, CTC showed varied electrostatic charge (+1, 0 and -1, respectively) which affected its adsorption. The results indicated that CTC followed Langmuir isotherm and the related parameters were calculated. Also, it was observed that the maximum adsorption occurred at pH1. The adsorption capacity of CTC for raw and activated biochar was at least 2.1 and 208.3mg/g adsorbent, respectively. The characteristics of biochars were studied using zeta potential analyzer, laser size analyzer and scanning electron microscopy (SEM). The results showed that raw and activated biochars are promising candidates for removal of CTC from water due to the acidic character of pinewood that can result in better interaction with ionizable compounds at lower pHs.

C/Si multilayer mirrors for the 25–30-nm wavelength region

We report a new material combination, C/Si, for normal-incidence multilayer mirrors in the wavelength region 25-30 nm. The multilayers, fabricated by ion-beam-sputtering deposition, were characterized by near-normal-incidence reflectance measurements by using a discharge source and a grazing-incidence monochromator. The highest measured near-normal-incidence reflectance was R = 23% (25.6 nm), R = 20% (28.3 nm), R = 25% (30.4 nm) at incident angles of 10 degrees , 12 degrees , and 4 degrees , respectively. The multilayers were also characterized by transmission electron microscopy, which revealed sharp layer interfaces and low interfacial roughness.

IR and x-ray studies of ion-beam-synthesized aluminium nitride films

IR transmission spectroscopy in conjunction with X-ray diffraction was used to characterize the phase composition of aluminium films after nitrogen ion implantation. Aluminium films deposited onto single-crystal silicon and implanted with 30 keV nitrogen ions (14N2+) to a dose of 1017-1018 ions cm-2 were subsequently characterized for aluminium nitride (AIN) formation by IR spectroscopy. The formation of a stoichiometric AIN layer was evident from the IR absorption band observed at 648 cm-1. Furthermore, X-ray diffraction of an aluminium foil after nitrogen implantation at 110 keV to a dose of 5.0 × 1017 ions cm-2 on each side revealed the presence of a polycrystalline AIN phase. A thermal treatment at 700°C did not yield any new crystalline phases.

Hydrogen sorption properties of vanadium- and palladium-implanted magnesium films

Abstract Magnesium films prepared by vacuum evaporation were implanted with vanadium and palladium ions in order to study their hydrogenation characteristics. It was found that the hydrogenation kinetics depend on the ion species and on the ion dose implanted. Indeed, the vanadium-implanted magnesium films have faster kinetics than the palladium-implanted ones. However, low vanadium concentration (∼0.3 at.%) seems to inhibit the absorption reaction. Among the ion-implanted magnesium films, the fastest kinetics were obtained with the vanadium-implanted film at a dose of 1×1016 ions/cm2: at 623 K and under a hydrogen pressure of 10 bar, a concentration of 6 wt.% of hydrogen was reached in 270 min during the first hydrogenation and in 45 min during the second one.