Sökning: "relative frequency"

Visar resultat 6 - 10 av 349 avhandlingar innehållade orden relative frequency.

1. 6. Applications of Short Extreme Ultraviolet Pulses to the Spectroscopy of Atoms and Molecules

   Författare :Allan Johansson; Atomfysik; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; High-order harmonics; short pulses; pulse characterisation; sidebands; lifetime measurements; time domain spectroscopy; frequency domain spectroscopy; He; N2; CO; XUV; Atomic and molecular physics; relative polarisation; Atom- och molekylärfysik; Fysicumarkivet A:2003:Johansson;

   Sammanfattning : This thesis is devoted to the characterisation in time and frequency, and to spectroscopic application, of extreme ultraviolet (XUV) pulses. High-order harmonic generation or wave mixing processes were used to produce the pulses in the XUV spectral region. LÄS MER

3. 7. Fiber-laser-based noise-immune cavity-enhanced optical heterodyne molecular spectrometry

   Författare :Aleksandra Foltynowicz; Ove Axner; Weidong Chen; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; absorption spectrometry; frequency modulation; cavity enhancement; NICE-OHMS; Laser frequency stabilization; fiber laser; Fabry-Perot cavities; sub-Doppler spectroscopy; trace gas detection; Physics; Fysik; Molecular physics; Molekylfysik; fysik; Physics;

   Sammanfattning : Noise-immune cavity-enhanced optical heterodyne molecular spectro-metry (NICE-OHMS) is one of the most sensitive laser-based absorption techniques. The high sensitivity of NICE-OHMS is obtained by a unique combination of cavity enhancement (for increased interaction length with a sample) with frequency modulation spectrometry (for reduction of noise). LÄS MER

4. 8. Computational electromagnetics : software development and high frequency modeling of surface currents on perfect conductors

   Författare :Sandy Sefi; Jesper Oppelstrup; Francisco Saez de Adana; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; High frequency approximations; Maxwell’s equations; Method of Moments; Physical Optics; Geometrical Theory of Diffraction; Extraction Extrapolation; Numerical analysis; Numerisk analys;

   Sammanfattning : In high frequency computational electromagnetics, rigorous numerical methods be come unrealistic tools due to computational demand increasing with the frequency. Instead approximations to the solutions of the Maxwell equations can be employed to evaluate th electromagnetic fields. LÄS MER

5. 9. Low noise frequency combs and their use in broadly tunable lasers and optical coherence tomography

   Författare :Connor Skehan; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Optical frequency comb; optical injection locking; comb noise;

   Sammanfattning : Frequency combs revolutionized the world of laser physics by providing a link between the microwave and optical domains. Such a link allows for precise knowledge of any comb line’s absolute average location, as well as the average spacing between any two comb lines. LÄS MER

7. 10. Hybrid Methods for Computational Electromagnetics in Frequency Domain

   Författare :Stefan Hagdahl; Björn Engquist; Lars Pettersson; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Maxwell s equations; Geometrical Theory of Diffraction; Smooth Surface Diffraction; Boundary Element Method; Hybrid methods; Electromagnetic Scattering; Numerical analysis; Numerisk analys;

   Sammanfattning : In this thesis we study hybrid numerical methods to be used in computational electromagnetics. The purpose is to address a wide frequency range relative to a given geometry. We also focus on efficient and robust numerical algorithms for computing the so called Smooth Surface Diffraction predicted by Geometrical Theory of Diffraction (GTD). LÄS MER