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Acoustic Wavelength

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Semere A Tadesse – One of the best experts on this subject based on the ideXlab platform.

  • sub optical Wavelength Acoustic wave modulation of integrated photonic resonators at microwave frequencies
    Nature Communications, 2014
    Co-Authors: Semere A Tadesse
    Abstract:

    Light-sound interactions have long been exploited in various acousto-optic devices based on bulk crystalline materials. Conventionally, these devices operate in megahertz frequency range where the Acoustic Wavelength is much longer than the optical Wavelength and a long interaction length is required to attain significant coupling. With nanoscale transducers, Acoustic waves with sub-optical Wavelengths can now be excited to induce strong acousto-optic coupling in nanophotonic devices. Here we demonstrate microwave frequency surface Acoustic wave transducers co-integrated with nanophotonic resonators on piezoelectric aluminum nitride substrates. Acousto-optic modulation of the resonance modes at above 10 GHz with the Acoustic Wavelength significantly below the optical Wavelength is achieved. The phase and modal matching conditions in this scheme are investigated for efficient modulation. The new acousto-optic platform can lead to novel optical devices based on nonlinear Brillouin processes and provides a direct, wideband link between optical and microwave photons for microwave photonics and quantum optomechanics.

  • Sub-optical Wavelength Acoustic wave modulation of integrated photonic resonators at microwave frequencies
    Nature Communications, 2014
    Co-Authors: Semere A Tadesse
    Abstract:

    Light–sound interactions have long been exploited in various acousto-optic devices based on bulk crystalline materials. Conventionally, these devices operate in megahertz frequency range where the Acoustic Wavelength is much longer than the optical Wavelength and a long interaction length is required to attain significant coupling. With nanoscale transducers, Acoustic waves with sub-optical Wavelengths can now be excited to induce strong acousto-optic coupling in nanophotonic devices. Here we demonstrate microwave frequency surface Acoustic wave transducers co-integrated with nanophotonic resonators on piezoelectric aluminum nitride substrates. Acousto-optic modulation of the resonance modes at above 10 GHz with the Acoustic Wavelength significantly below the optical Wavelength is achieved. The phase and modal matching conditions in this scheme are investigated for efficient modulation. The new acousto-optic platform can lead to novel optical devices based on nonlinear Brillouin processes and provides a direct, wideband link between optical and microwave photons for microwave photonics and quantum optomechanics. Acousto-optic modulators use Acoustic waves to control light on a chip. Here, the authors achieve modulation in nanophotonic resonators using microwave frequency surface Acoustic waves with Wavelength smaller than the optical Wavelength towards highly integrated devices on silicon.

M Parmar – One of the best experts on this subject based on the ideXlab platform.

  • mean force on a finite sized spherical particle due to an Acoustic field in a viscous compressible medium
    Physical Review E, 2014
    Co-Authors: Subramanian Annamalai, S Balachandar, M Parmar
    Abstract:

    An analytical expression to evaluate the second-order mean force (Acoustic radiation force) on a finite-sized, rigid, spherical particle due to an Acoustic wave is presented. The medium in which the particle is situated is taken to be both viscous and compressible. A far-field derivation approach has been used in determining the force, which is a function of the particle size, Acoustic Wavelength, and viscous boundary-layer thickness. It is assumed that the viscous length scale is negligibly small compared to the Acoustic Wavelength. The force expression presented here (i) reduces to the correct inviscid behavior (for both small- and finite-sized particles) and (ii) is identical to recent viscous results [M. Settnes and H. Bruus, Phys. Rev. E 85, 016327 (2012)] for small-sized particles. Further, the computed force qualitatively matches the computational fluifluid dynamics (finite-element) results [D. Foresti, M. Nabavi, and D. Poulikakos, J. Fluid Mech. 709, 581 (2012)] for finite-sized particles. Additionally, the mean force is interpreted in terms of a multipole expansion. Subsequently, considering the fact that the force expansion is an infinite series, the number of terms that are required or adequate to capture the force to a specified accuracy is also provided as a function of the particle size to Acoustic Wavelength ratio. The dependence of the force on particle density, kinematic viscviscosity, and bulk viscosity of the fluid is also investigated. Here, both traveling and standing waves are considered.

B Sylla – One of the best experts on this subject based on the ideXlab platform.

  • Simple Acoustic multiplexer.
    Physical Review E, 2005
    Co-Authors: Leonard Dobrzynski, Piotr Zieliński, Abdellatif Akjouj, B Sylla
    Abstract:

    Simple structures enabling the multiplexing of Acoustic waves are presented. Such structures are constructed out of two monomode Acoustic wires and two masses bound together, and to the wires by springs. We show analytically that these simple structures can transfer with selectivity and in one direction one Acoustic Wavelength from one wire to the other, leaving neighbor Acoustic Wavelengths unaffected. We give closed-form relations enabling to obtain the values of the relevant physical parameters for this multiplexing phenomena to happen at a chosen Wavelength. Finally, we illustrate this general theory by an application.

Stephen P. Morgan – One of the best experts on this subject based on the ideXlab platform.

  • Effect of object size and Acoustic Wavelength on pulsed ultrasound modulated fluorescence signals.
    Journal of biomedical optics, 2012
    Co-Authors: Nam Huynh, Haowen Ruan, Barrie Hayes-gill, Stephen P. Morgan
    Abstract:

    Detection of ultrasound (US)-modulated fluorescence in turbid media is a challenge because of the low level of fluorescent light and the weak modulation of incoherent light. A very limited number of theoretical and experimental investigations have been performed, and this is, to our knowledge, the first demonstration of pulsed US-modulated fluorescence tomography. Experimental results show that the detected signal depends on the Acoustic frequency and the fluorescent target’s size along the ultrasonic propagation axis. The modulation depth of the detected signal is greatest when the length of the object along the Acoustic axis is an odd number of half Wavelengths and is weakest when the object is an integer multiple of an Acoustic Wavelength. Images of a fluorescent tube embedded within a 22- by 13- by 30 mm scattering gel phantom (μ(s)∼15  cm(-1), g=0.93) with 1-, 1.5-, and 2 MHz frequency US are presented. The modulation depth of the detected signal changes by a factor of 5 depending on the relative size of the object and the frequency. The approach is also verified by some simple experiments in a nonscattering gel and using a theoretical model.

Subramanian Annamalai – One of the best experts on this subject based on the ideXlab platform.

  • mean force on a finite sized spherical particle due to an Acoustic field in a viscous compressible medium
    Physical Review E, 2014
    Co-Authors: Subramanian Annamalai, S Balachandar, M Parmar
    Abstract:

    An analytical expression to evaluate the second-order mean force (Acoustic radiation force) on a finite-sized, rigid, spherical particle due to an Acoustic wave is presented. The medium in which the particle is situated is taken to be both viscous and compressible. A far-field derivation approach has been used in determining the force, which is a function of the particle size, Acoustic Wavelength, and viscous boundary-layer thickness. It is assumed that the viscous length scale is negligibly small compared to the Acoustic Wavelength. The force expression presented here (i) reduces to the correct inviscid behavior (for both small- and finite-sized particles) and (ii) is identical to recent viscous results [M. Settnes and H. Bruus, Phys. Rev. E 85, 016327 (2012)] for small-sized particles. Further, the computed force qualitatively matches the computational fluid dynamics (finite-element) results [D. Foresti, M. Nabavi, and D. Poulikakos, J. Fluid Mech. 709, 581 (2012)] for finite-sized particles. Additionally, the mean force is interpreted in terms of a multipole expansion. Subsequently, considering the fact that the force expansion is an infinite series, the number of terms that are required or adequate to capture the force to a specified accuracy is also provided as a function of the particle size to Acoustic Wavelength ratio. The dependence of the force on particle density, kinematic viscosity, and bulk viscosity of the fluid is also investigated. Here, both traveling and standing waves are considered.