Browse Prior Art Database

Tunable Optical Filter

IP.com Disclosure Number: IPCOM000093696D
Original Publication Date: 1966-Jan-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 23K

Publishing Venue

IBM

Related People

Weider, H: AUTHOR

Abstract

This device accepts a beam 5 of light polarized perpendicular to the plane of the paper and composed of a wide band of wavelengths. The device provides a beam of linearly polarized light 5' of a single wave length. Plates 7 exhibiting the Faraday effect are oriented at Brewster's angle with respect to the direction of oncoming beam 5. The thickness of each plate 7 is chosen so that it provides at least 180 degrees of rotation plane of polarization for the full band of wavelengths with reasonable values of the magnetic field H. Because of the dispersion of the Faraday effect in material 7, a given value of H results in 180 degree rotation of the plane of polarization for a unique wavelength. All other wavelengths are rotated more than, or less than, 180 degrees.

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Tunable Optical Filter

This device accepts a beam 5 of light polarized perpendicular to the plane of the paper and composed of a wide band of wavelengths. The device provides a beam of linearly polarized light 5' of a single wave length. Plates 7 exhibiting the Faraday effect are oriented at Brewster's angle with respect to the direction of oncoming beam 5. The thickness of each plate 7 is chosen so that it provides at least 180 degrees of rotation plane of polarization for the full band of wavelengths with reasonable values of the magnetic field H. Because of the dispersion of the Faraday effect in material 7, a given value of H results in 180 degree rotation of the plane of polarization for a unique wavelength. All other wavelengths are rotated more than, or less than, 180 degrees.

With the incoming beam polarized perpendicular to the plane of the paper, the unique wavelength passes through the series of plates 7 without any attenuation caused by reflection at an interface. The only losses are those of absorption within material 7. All other wavelengths suffer additional losses at each interface by partial reflection.

By using many such plates 7 in tandem, the resulting light consists of a narrow band of wavelengths, with a peak centered at the unique wavelength. A change in the external magnetic field H produces a corresponding change in the value of the peak wavelength.

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