Browsing by Subject "Optical waveguide"

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    Silicon-on-insulator optical waveguides and waveguide devices
    (2000) Kiyat, İsa
    Silicon-on-insulator(SOI) optical waveguides, directional couplers and some types of MMI couplers were designed, fabricated and characterized at a wavelength of 1.55 /im. Effective index method and the single mode condition for rib waveguide was used in design of optical waveguides. BPM simulations were extensively employed for all fabricated devices. Waveguides and the other devices were defined on SOI material by wet chemical etching in KOH solutions^ Fabricated devices were characterized on a standard fiber optic measurement setup with a DFB laser as its IR light source. In characterization of optical waveguides the single mode condition was verified and insertion loss was measured to be 12.2 dB for TE and 12.7 dB for TM polarized light as the best values. Furthermore, the propagation loss found to be 0.70 dB/cm for TE and 0.76 dB/cm for TM which is typical . Characterized directional couplers gave results completely consistent with their BPM simulations. 1x2, 2x2, 1x4 and 1x8 type MMI couplers were also found to gave expected behaviors. Splitting ratios as low as 0 dB and 0.55 dB was measured.
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    Superconducting and electro-optical thin films prepared by pulsed laser deposition technique
    (Elsevier, 2000-12-15) Schubert, J.; Siegert, M.; Fardmanesh, M.; Zander, W.; Prompers, M.; Cuchal, C.; Lisoni, J.; Lei, C. H.
    The pulsed laser deposition (PLD) technique is an excellent method to prepare single crystalline complex oxide thin films. We have successfully grown films for the use in HTS SQUID-devices as well as for thin film optical waveguides. The Josephson junction used in the HTS SQUIDs is formed by a step edge type gain boundary junction. The step preparation is a very critical process in the SQUID preparation to achieve reproducible low 1/f noise devices. We have established a new ion beam etching process to achieve clean and steep edges in LaAlO(3) (100) substrates. The 1/f noise of SQUIDs prepared with the new method is drastically reduced. In the process of developing thin film electro-optical waveguide modulators we investigated the influence of different substrates on the optical and structural properties of epitaxial BaTiO(3) thin films. These films are grown on MgO(1 0 0), MgAl(2)O(4)(1 0 0), SrTiO(3)(1 0 0) and MgO buffered Al(2)O(3)(1 (1) over bar 0 2) substrates. The waveguide losses and the refractive indices were measured with a prism coupling setup. The optical data are correlated to the results of Rutherford backscattering spectrometry/ion channeling (RBS/C), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy (TEM). The dielectric constant, the ferroelectric hysteresis loop and the transition temperature (ferroelectric to paraelectric state) of the BaTiO(3) thin films are measured. (C) 2000 Elsevier Science B.V. All rights reserved.