Patent
1989-05-31
1990-08-28
Arnold, Bruce Y.
35016224, 350166, 350316, 350311, G02B 500, G02B 1300
Patent
active
049520253
ABSTRACT:
A rugate type thin film optical interference filter is disclosed. Rugate filters are gradient-index optical filters in which the index of refraction of the film varies sinusoidally with thickness. Gradient-index filters vary the index of refraction continuously with thickness, instead of discontinuously as in, for example, quarter-wave stacks of alternating discrete layers of high and low refractive index. Rugate filters are generally used as narrow bandwidth blocking, or rejection, filters in which the specific wavelength of light reflected, or blocked, is directly proportional to the period of a simple sine wave that describes the refractive index profile of the film. Multiple-line rejection filters, in which more than one wavelength, or line, is reflected, are made by superimposing individual sine waves in parallel. The present invention provides a more easily made rugate filter by reducing the maximum required peak-to-peak refractive index modulation within the film. This is accomplished by having the sine wave for rejecting the longest wavelength line extend through the refractive index profile for the entire film thickness and connecting the sine waves for rejecting shorter wavelength lines in series and superimposing them with the sine wave for rejecting the longest wavelength line. It also enables the fabrication of rugate filters having more individual reflectance bands of similar bandwidth than would otherwise be possible with a given pair of materials.
REFERENCES:
patent: 3846152 (1972-05-01), Franz
patent: 4395098 (1983-07-01), Mahlein
patent: 4583822 (1986-04-01), Southwell
patent: 4602287 (1986-07-01), Fockens
patent: 4673270 (1987-06-01), Gordon
patent: 4707611 (1987-11-01), Southwell
patent: 4735488 (1988-04-01), Rancourt et al.
patent: 4819239 (1989-04-01), Sharp et al.
patent: 4826267 (1989-05-01), Hall et al.
patent: 4837044 (1989-06-01), Murarka et al.
Gradient-Index Antireflection Coatings W. H. Southwell, W. H. Southwell, Jul. 5, 1983 Rockwell International Science Center, Thousand Oaks, Calif. 91360.
Arnold Bruce Y.
Nguyen Thong
Sinder Frederic L.
Singer Donald J.
The United States of America as represented by the Secretary of
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