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Proceedings Paper

Understanding beam alignment in a coherent lidar system
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Paper Abstract

Optical beam alignment in a coherent lidar (or ladar) receiver system plays a critical role in optimizing its performance. Optical alignment in a coherent lidar system dictates the wavefront curvature (phase front) and Poynting vector) matching of the local oscillator beam with the incoming receiver beam on a detector. However, this alignment is often not easy to achieve and is rarely perfect. Furthermore, optical fibers are being increasingly used in coherent lidar system receivers for transporting radiation to achieve architectural elegance. Single mode fibers also require stringent mode matching for efficient light coupling. The detector response characteristics vary with the misalignment of the two pointing vectors. Misalignment can lead to increase in DC current. Also, a lens in front of the detector may exasperate phase front and Poynting vector mismatch. Non-Interaction of Waves, or the NIW property indicates the light beams do not interfere by themselves in the absence of detecting dipoles. In this paper, we will analyze the extent of misalignment on the detector specifications using pointing vectors of mixing beams in light of the NIW property.

Paper Details

Date Published: 1 October 2013
PDF: 7 pages
Proc. SPIE 8832, The Nature of Light: What are Photons? V, 88320A (1 October 2013); doi: 10.1117/12.2025460
Show Author Affiliations
Narasimha S. Prasad, NASA Langley Research Ctr. (United States)
Chandrasekhar Roychoudhuri,, Univ. of Connecticut (United States)


Published in SPIE Proceedings Vol. 8832:
The Nature of Light: What are Photons? V
Chandrasekhar Roychoudhuri; Al F. Kracklauer; Hans De Raedt, Editor(s)

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