Annular Gaussian beams in turbulent media
2004 (English)In: FREE-SPACE LASER COMMUNICATION AND ACTIVE LASER ILLUMINATION III, BELLINGHAM: SPIE-INT SOC OPTICAL ENGINEERING , 2004, Vol. 5160, 86-97 p.Conference paper (Refereed)
A laser beam with a different irradiance profile may have favorable scintillation and diffraction characteristics, which are important qualities in the area of optical wireless communication. The propagation in random media (atmosphere) of a laser beam with an annular, donut-shaped, irradiance cross section was examined. Annular beams are created by unstable optical resonators, which are used as resonant cavities in high power lasers, and by beam expanders that consist of telescopes where the second mirror obstruct the central portion of the circular aperture. The annular beam was modeled as the difference of two collimated Gaussian beams, with different spot sizes. Diffraction and scintillation characteristics of the annular beam, for horizontal near ground propagation (i.e. constant refractive-index structure parameter C-n(2)), were compared to one collimated and one focused Gaussian beam. The Rytov approximation was used to calculate the on-axis scintillation index in weak atmospheric turbulence for both the annular and the Gaussian beams. The extended Huygens-Fresnel integral was solved to obtain the mean irradiance, from which the fraction of power in half aperture diameter was calculated.
Place, publisher, year, edition, pages
BELLINGHAM: SPIE-INT SOC OPTICAL ENGINEERING , 2004. Vol. 5160, 86-97 p.
, PROCEEDINGS OF THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS (SPIE), ISSN 0277-786X
atmospheric turbulence, scintillation, annular beam, donut beam
Atom and Molecular Physics and Optics
IdentifiersURN: urn:nbn:se:kth:diva-43937DOI: 10.1117/12.507774ISI: 000189421100009ISBN: 0-8194-5033-2OAI: oai:DiVA.org:kth-43937DiVA: diva2:451253
Qc 201110252011-10-252011-10-192011-11-01Bibliographically approved