Sökning: "zero group velocity"

Hittade 4 avhandlingar innehållade orden zero group velocity.

  1. 1. Thin Film Plate Acoustic Resonators for Frequency Control and Sensing Applications

    Författare :Lilia Arapan; Ventsislav Yantchev; Ilja Katardjiev; Enrique Iborra; Uppsala universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Electro-Acoustics; FPAR; Lamb waves; aluminium nitride; interdigital transducer; phase noise; temperature compensation; power handling; sensitivity; zero group velocity; intermode coupling; Teknisk fysik med inriktning mot elektronik; Engineering Science with specialization in Electronics; Teknisk fysik med inriktning mot mikrosystemteknik; Engineering Science with specialization in Microsystems Technology;

    Sammanfattning : The recent development of the commercially viable thin film electro-acoustic technology has triggered a growing interest in the research of plate guided wave or Lamb wave components owing to their unique characteristics. In the present thesis i) an experimental study of the thin film plate resonators (FPAR) performance operating on the lowest symmetrical Lamb wave (S0) propagating in highly textured AlN membranes versus a variety of design parameters has been performed. LÄS MER

  3. 2. Lamb wave evaluation of concrete plates

    Författare :Oskar Tofeldt; Teknisk geologi; []
    Nyckelord :Lamb waves; guided waves; impact-echo; concrete; non-destructive evaluation;

    Sammanfattning : This thesis is about the application of Lamb waves for non-destructive evaluation of plate-like concrete structures under one-sided access test condition using a portable equipment consisting of an accelerometer and impact hammer. With this type of equipment and based on array signal processing, the impact-echo (IE) method can be extended with measurements of surface waves; this extension allows an evaluation with Lamb waves. LÄS MER

  4. 3. Contributions to the Study of Nonlinear Optics

    Författare :Mats Desaix; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY;

    Sammanfattning : Nonlinear optics, the study of how high intensity light propagates through and interacts with matter, is a subject which is rich in scientific problems and offers many technologically important applications. In this thesis, a number of physical and mathematical problems concerning nonlinear Kerr media are addressed. LÄS MER

  5. 4. Optical Parametric Devices in Periodically Poled LiTaO3

    Författare :Martin Levenius; Katia Gallo; Valdas Pasiskevicius; Giuseppe Leo; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; nonlinear optics; parametric processes; frequency downconver-sion; quasi-phase matching; LiTaO3; broadband downconversion; quadratic cascading; nonlinear photonic crystals; twin-beam generation;

    Sammanfattning : Optical parametric frequency conversion based on quasi phase matching (QPM) in nonlinear optical crystals is a powerful technique for generating coherent radiation in wavelength ranges spanning from the mid-infrared (mid-IR) to the blue, displaying low thermal load and high efficiency.This thesis shows how QPM in one- (1D) or two-dimensional (2D) lattices can be employed to engineer novel devices for parametric downconversion in the IR, af-fording freedom in designing both spectral and angular properties of the parametric output. LÄS MER