Thirty Years Ago!. At the Max Planck CdTe Resonant Brillouin Scattering

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  • Thirty Years Ago!

  • At the Max PlanckCdTeResonant Brillouin Scattering

  • Membrane Acoustics: Nanostructures to biological tissues Supported layers standing resonancesSiON/GaAs; ZnSe/GaAsFreestanding NanomembranesSiNSiN/PolymerPatterned nanowires

    Cornea and eye lens

  • Longitudinal Standing ModesSiO3N4/ GaAsZnSe/ GaAs

  • Organ Pipe Modes

    d=3/4, f=3V/4d,Second harmonicd=, f=V/dSecond harmonic

  • Scattering IntensityElasto-Optic Contributions Film + SubstrateBortolani, Marvin, Nizzoli, Santoro J. Phys. C. 16, 1757 (1983)E-O

  • Scattering Intensity

  • ZnSe/GaAs: BLS Intensity

  • Freestanding membranesUltra-light weight Robust, pliable, flexible electronicsMechanical/ elastic propertiesProximity of surfaces ~ phonon wavelengthsLattice vibrations modifiedIncreased phonon relaxation ratesNano-scale heat transport; Quantized thermal conductance Consequence on electron transportComposite hard-soft (inorganic-polymer) membranesPhonon isolation Lithography on soft layerNano-wires/ lines

  • Freestanding Si3N4 membraneLSM, TSM, Dilational, Flexural Modes

  • Freestanding Si3N4-PMMA bilayer nano-membranes

  • PMMA/SiN: dispersion

  • Nanowires

  • Nano-wire DispersionOdd parityEven parityResonant Ultrasound Spectroscopy (Migliori)

  • In-plane Dispersion

  • Mode Profiles2TSMEdge type1TSM1TSMm= 0TSMq1= qx = m/w,q2= qy = 0

  • Mode ProfilesFinite q

  • Human LensSoft outer cortex, stiff inner nucleusTransition between stiff nucleus to soft cortex results in mode doubletNo change in frequency and bulk modulus with age (B = 2 2/4n2).

    Heys KR, Molecular Vision (2004)

  • Bovine Lens and CorneaProbe intact bovine eye globe, power ~5mW.Frequency (bulk modulus) profile mapped through axial depth of eye globe.Corneal modulus (BLS) excellent agreement with ultrasonics on same location Cortex-nucleus transition in bovine lens not seen.Corneal and lenticular thickness, distance between cornea and lens measured.Probe fibril structure in cornea?Bulk Modulus:Human Lens: 3.7 GPa, Bovine Lens: 4.1 GPa,Bovine Cornea: 2.6 GPa

    Mission, G. Ophthal. Physiol. Opt. 2007 27: 256-264.

  • ConclusionsBLS of elasticity on nanoscale structuresStanding wave modes (LSM, TSM) distinct role of ripple and e-o contributionsFlexural and Dilational modesMode confinement across width and height of rectangular wires role of sidewalls in trench structuresCorneal and Lens studies non-invasive probe with potential clinical relevance