Jarmila Spirkova

A study of the preparation and properties of copper-containing optical planar glass waveguides

Abstract We have studied the fabrication and properties of the Cu + -containing waveguides. These waveguides were fabricated in a special soda-lime silicate glass as well as in commercial optical glass substrates, by using an ion exchange in the melts containing either Cu + or Cu 2+ , at temperatures from 350°C to 500°C, and for periods from 5 min to 21 h. The optical properties of the fabricated waveguides were characterized using both mode and photoluminescence spectroscopy. The composition of waveguiding layers was studied using Rutherford Backscattering Spectrometry (RBS) and ESCA. The presence of divalent copper was determined using Electron Paramagnetic Resonance (EPR). After ion exchange, the refractive index increased, depending on the fabrication conditions, up to Δ n =+0.0693, and the waveguides supported up to 16 TE and TM modes. The depths of the fabricated waveguides varied between 6.0 and 27.5 μm. The most intensive blue-green luminescence was achieved with the samples that were ion-exchanged in the Cu 2 Cl 2 ·ZnCl 2 melt, where the presence of Zn 2+ strongly impeded the oxidation of Cu + to Cu 2+ . Both oxidation states of copper (Cu + as well as Cu 2+ ) were found in the waveguides fabricated in the pure Cu 2 Cl 2 . The main advantage of the copper-containing waveguides is the possibility of integrating the passive and active functions of the waveguides on the same substrate.

Er–Yb Waveguide Amplifiers in Novel Silicate Glasses

A set of novel silicate glasses containing ZnO and co-doped with Er3+ and Yb3+ was designed as substrates for optical waveguide amplifiers. Characterized by exceptionally low up-conversion, minimum Er concentration quenching and high mechanical as well as chemical stability, the reported glasses can compete with phosphate-based materials typically used in the state-of-art active devices. Straight channel waveguides with propagation losses as low as 0.18 dB/cm were fabricated in these substrates using Ag+ hArr Na+ and K + hArr Na+ thermal ion exchange. Net on-chip gain values of 6.7 dB at 1537 nm were measured and a net fiber to-fiber gain of 5 dB was achieved when pumped at 976 nm. A six-level spatially resolved numerical model of an Er-Yb co-doped active waveguide was developed to analyze and optimize the amplifier performance. Modification of the rare-earth dopant concentration and the channel waveguide geometry was proposed to increase the gain figure and improve the overall amplifier efficiency.

Copper Doped Waveguides in Glass Substrates

We have studied the fabrication and properties of the copper ion exchanged waveguides that were fabricated in special Na 2 O-rich soda-lime silicate glasses and in commercial BK7 optical glass substrates. The ion exchange was performed in melts containing either Cu I or Cu II at temperatures from 350°C to 500°C for times ranging from 5 min to 21 h. Optical properties of the fabricated waveguides were studied using mode spectroscopy and photoluminescence spectroscopy, and composition of the waveguides was determined by using Scanning Electron Microscope (SEM), Rutherford Backscattering Spectrometry (RBS), Electron Paramagnetic Resonance (EPR), and Electron Spectroscopy for Chemical Analysis (ESCA). After the ion exchange the refractive index increased, according to fabrication conditions, up to j n = +0.0693, and the guides supported up to 16 TE and TM modes. The Cu I 5 Cu II redox reaction during the fabrication depended strongly on the composition as well as the temperature of the reaction melts. In the Cu 2 Cl 2 :ZnCl 2 melts, the oxidation of Cu I to Cu II was strongly impeded, so that Cu I prevailed in the waveguiding region. These samples exhibited the most intensive blue-green luminescence in spite of those fabricated by using the Cu II -based reaction melts, where practically no blue-green luminescence was observed. ESCA measurement revealed an easy charge transfer between both oxidation states of copper in the very surface regions of the samples.

Features of APE waveguides in different Er:LiNbO3 and (Er + Yb):LiNbO3 cuts: electrooptical coefficient r33

Abstract Our contribution represents a systematic study of optical layers fabricated by the annealed proton exchange (APE) method in various cuts (X, Y, Z) of lithium niobate that was doped in bulk with erbium (500 ppm) and mixture of erbium and ytterbium in weight portion 1:9 (1000 ppm). Rutherford backscattering spectrometry (RBS), elastic recoil detection analysis (ERDA) and neutron depth profiling (NDP) methods have been used for monitoring a composition of fabricated optical layers, i.e. changes of the concentration of the rare earths (RE), hydrogen and lithium. We have used mode spectroscopy and a Mach–Zehnder interferometer to monitor the relevant properties, i.e. changes in the effective refractive index and the electrooptical coefficient r33. The obtained results show that during the APE process, there is no loss of the rare earths from the substrate and that during the treatment of the as-exchanged samples the hydrogen concentration increases while the lithium concentration decreases. Waveguiding properties and composition of the RE doped waveguides were not substantially changed compared with those fabricated in pristine lithium niobate. The presence of the doping ions decreases the r33, however, a carefully designed APE technology can increase the r33 almost to the value of the pristine LiNbO3. A correlation between the uniform distribution of lithium and high values of the electrooptic coefficient r33 was found. According to our results the proton exchange not necessarily lowers the efficiency of the 1.5 μm emission and certainly does not lower the concentration of the RE.

The effect of Ca2+, Mg2+, and Zn2+ on optical properties of Er3+ doped silicate glass

To investigate the effect of divalent cations, we melted a set of sodium silicate baseline glasses with different concentrations of Ca2+, Mg2+, and Zn2+. We doped each of these basic glass matrices with several different amounts of Er3+ cations. These samples have been characterized in terms of absorption spectra, luminescence spectra, and experimental lifetime of the erbium metastable state. We also fabricated planar waveguides using Ag+/Na+ ion-exchange process. Characteristic parameters of the waveguides such as the number of modes, the refractive index change, the depth of the diffused region, and the propagation loses were measured. The mutual replacements of the divalent cations influenced the electron donor power (basicity) of oxygen atoms coordinating metal ions in glass. Measured optical spectra, lifetime values, and waveguiding parameters reflected the changes in glass basicity. To quantify the individual effects of Ca2+, Mg2+, and Zn2+, we calculated composition-property models based on polynomial functions with multiple variables. Correlation coefficients R2 varied from 0.991 to 1.000 indicating good linear correlations between the parameters and composition. The evaluation of glass component effects on the studied parameters enabled us quantify the chemical influence of the divalent cations. We discussed this influence using the optical basicity theory that predicts the variations of the electron donor power of oxygen atoms with glass composition. The knowledge of component effects is very useful for the effective formulation of new glass compositions. New Er glasses containing Zn2+ and/ or Mg2+ as divalent cations are promising materials for optical waveguide amplifiers.

Characterisation of hydrogen and erbium in carbon layers fabricated by PACVD for optical applications

Abstract Carbon films prepared by plasma assisted chemical vapor deposition were doped by laser active ion Er 3+ . The characterisation of the layers was performed using Rutherford backscattering spectrometry and elastic recoil detection analysis. Optical properties of the waveguides were measured at 660 nm wave length using standard prism spectroscopy. The correlation between the layer composition and the content of incorporated erbium and layer optical properties shows very interesting aspects [SPIE 4281, San Jose (2001) 13].

Design and modelling of the integrated polymer microring resonators on silicon substrate

We report about new polymer optical microresonators (OM) optical filters designed for operating wavelengths 1550 nm and filtering out wavelength 1490 nm. The first step was to design a single mode polymer waveguide by using BeamPROP™ software and after that a microring resonators were designed by Finite-Difference Time-Domain method using FullWAVE™ software. We also did modelling of three types of polymer waveguides for MR design structures. For all the structures we used Epoxy Novolak Resin polymer as core waveguide layer deposited on silicon substrate with a buffer layer between them. Three types of buffer layer were used - silica, Polymethylmethacrylate or Cytop layer while PMMA or Cytop were used as cover protection layer. Waveguides without cover protection layer were designed as well. Modelling of a single OM shows that the signal at 1490 nm is not sufficiently filtered out while the triple OM has sufficient transmission characteristics.

Optical properties of Dy3+ doped epoxy novolak resin

We report about properties of epoxy novolak resin polymer doped with dysprosium ions. The polymer layers were fabricated by spin-coating onto silicon substrates, or pouring epoxy novolak resin solution into bottomless molds placed on a quartz substrate and leaving them to dry. Rather strong bands around 3366 cm-1 in the infrared spectra indicated presence of the O-H groups. Absorption measurements were done in the spectral range from 300 nm to 3000 nm and showed six strong bands at 758 nm (6F3/2), 807 nm (6F5/2), 906 nm (6F7/2), 1100 nm (6F9/2), 1280 nm (6F11/2) and 1685 nm (6H11/2) corresponding to Dy3+ ions. Optical band gap Eg was determined from the absorption coefficient values using Taucs procedure, i.e., from the relationship αhv = A(hv - Eg)2 and the obtained values varied from 3.489 eV to 3.539 eV depending on the amount of dysprosium ions involved in the samples. Photoluminescence spectra around 1300 nm were investigated by using excitation of He-Ne laser (632.8 nm) and two semiconductor lasers (980 nm and 827 nm).

Investigation of GaN layers doped with Er3+ and Er3+ + Yb3+ ions using the transmittance measurement

We report about fabrication and properties of Gallium Nitride (GaN) layers doped with erbium or mixture of erbium and ytterbium ions. Transmission spectra in the spectral range from 280 to 800 nm taken by the spectrometer Varian Cary 50 showed that the increasing concentration of the dopants shifts the absorption edge to the lower wavelengths. Optical band gap Eg was determined from the absorption coefficient values using Taucs procedure and the obtained values varied from 3.08 eV to 3.89 eV depending on the erbium or erbium plus ytterbium doping. Photoluminescence emission at 1 530 nm due to the Er3+ intra-4f 4I13/2 → 4I15/2 transition was observed by using excitation of semiconductor lasers operating at 980 nm.

Optical Properties of Epoxy Novolak Resin Polymer Co-doped with Er3+ and Er3+/Yb3+ ions

We report about a fabrication and properties of Er³⁺ and Er³⁺/Yb³⁺ ions doped epoxy novolak resin. The polymer layers were fabricated by a spin coating and using ErCl₃ and YbCl₃ or ErF₃ and YbF₃ dissolved in C₅H₉NO for the Er and Yb doping.