Atomic layer deposited titanium dioxide in optical waveguiding applications

Tapani Alasaarela

    Research output: ThesisDoctoral ThesisCollection of Articles


    This thesis introduces the use of atomic layer deposited (ALD) amorphous titanium dioxide (TiO2) in various waveguiding applications. The ALD of amorphous TiO2 is done by sequential pulsing of titanium tetrachloride (TiCl4) and water vapors into a nitrogen carrier gas flow at relatively low deposition temperatures of below 120°C and in a medium vacuum. The optical properties of the amorphous TiO2 slab waveguides are studied in the visible and near-infrared wavelengths, and a propagation loss of <1 dB/cm at 1.55 micrometer wavelength is measured. The conformal growth mode of ALD is used to narrow down silicon slot and to smoothen waveguide edges with an amorphous TiO2 layer, which enables fabrication of silicon slot waveguides with thin air slots and relatively low losses of down to 7 dB/cm. ALD-TiO2 is also used to successfully fabricate novel absorbing polarization selective resonant gratings, and semi-wide bandwidth resonant waveguide reflectors. A novel way of fabricating a resonant waveguide grating by applying an ALD-TiO2 layer on a holographically written surface relief grating on an azobenzene polymer complex is introduced. Amorphous ALD-TiO2 shows an excellent performance in all the studied applications, and will very probably see use in various photonic devices in the future. The low growth temperature allows the fabrication of ALD-TiO2 waveguides on top of processed microchips, so ALD-TiO2 might also turn out to be a suitable material in building the optically interconnected microchips of the future.
    Translated title of the contributionAtomic layer deposited titanium dioxide in optical waveguiding applications
    Original languageEnglish
    QualificationDoctor's degree
    Awarding Institution
    • Aalto University
    • Honkanen, Seppo, Supervising Professor
    Print ISBNs978-952-60-4179-7
    Electronic ISBNs978-952-60-4180-3
    Publication statusPublished - 2011
    MoE publication typeG5 Doctoral dissertation (article)


    • atomic layer deposition
    • waveguide
    • silicon photonics
    • grating
    • titanium dioxide


    Dive into the research topics of 'Atomic layer deposited titanium dioxide in optical waveguiding applications'. Together they form a unique fingerprint.

    Cite this