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Proceedings Paper

Aspheric Geodesic Lenses In An Integrated Optics Spectrum Analyser
Author(s): G. F. Doughty; R. B. Wilson; J. Singh; R. M. De la Rue; S. Wright
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Paper Abstract

The design of lenses for an integrated optics spectrum analyser is critically examined. In this signal processing device, guided light is acousto-optically Bragg deflected by electrically generated surface acoustic waves, in directions determined by their frequencies. Single crystal LiNb03 is the preferred substrate material, and geodesic lenses are used for beam collimation and focusing. The lenses must be aspheric to overcome aberrations and to guide light into surrounding plane regions. The diverging beam of an infrared (0.85μm) semiconductor laser is edge-coupled into the waveguide, then collimated by a geodesic lens to a width of 7mm in the acousto-optic interaction region. The resultant deflected beams are focused by a second lens on a detector array having mm element snacing. The geodesic lens dimensions are 18.5mm focal length, lOmm diameter, 1.3mm centre depth, and 75μm maximum departure from spherical. Factors affecting the image structure, and hence frequency discrimination, are examined. Diffraction, and fitting a straight detector array to the focal circle, lead to images up to about 2.5μm wide. Crystal anisotropy and wave-guide scatter further degrade the image. Lens profile tolerances are about ±0.5 µm.

Paper Details

Date Published: 13 May 1981
PDF: 9 pages
Proc. SPIE 0235, Aspheric Optics: Design, Manufacture, Testing, (13 May 1981); doi: 10.1117/12.958959
Show Author Affiliations
G. F. Doughty, University of Glasgow (United Kingdom)
R. B. Wilson, University of Glasgow (United Kingdom)
J. Singh, University of Glasgow (United Kingdom)
R. M. De la Rue, University of Glasgow (United Kingdom)
S. Wright, University of Glasgow (United Kingdom)

Published in SPIE Proceedings Vol. 0235:
Aspheric Optics: Design, Manufacture, Testing
L. R. Baker; K. J. Rosenbruch, Editor(s)

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