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US5225930A
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Comb optical interference filter
Assignee: United States Department of the Air Force
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Filing: 1992-09-30
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Granted: 1993-07-06
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Expires: 2012-09-30
Abstract
Abstract High total transmission, tunable comb filter structures are described which comprise moderately thick layers of optical material having periodic or multiply periodic refractive index modulation features comprising a multiplicity of coherently-coupled, weakly-resonant optical cavities, resulting in and characterized by spectra of high order (5 or higher) relative to a fundamental (lowest order) cavity resonance, consisting of narrow, moderate to high density reflection lines occurring in one or more sets, each set being characterized by lines equally spaced by wave number if optical dispersion is neglected. Filters of the inversion can be structured to be tuned, electro-optically or mechanically such that the peaks within a spectral band of interest shift by one harmonic order and/or from one peak position to the next, to reflect or transmit light of any specific wavelength within a band. The individual features defining optical cavities may be thin compared to a wavelength of interest as, for example, when metal films are used as part of a singly periodic comb filter, or may consist of a section whose thickness is equal to several wavelengths, but which is short compared to a cavity length.
Inventors
- 👤 Peter L. Land
- 👤 Roger J. Becker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 13:43
CPC Classifications
G; G02; G02F; G02F1/00; G02F1/01; G02F1/21; G02B; G02B5/00; G02B5/20; G02B5/28; G02B5/285; G02B5/287; G02B26/00; G02B26/001
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
236 words
A comb type optical interference filter comprising: (a) a first plurality of layers f(u,v), u=1 to U, v=1 to V defining a second plurality of individual optical cavities C(u,v) of length L(u,v), u=1 to U, v=1 to V, where U and V are preselected integers and U not less than 2, each said optical cavity comprising a third plurality of subfilter elements f(u,v) each having a reflectance at most equal to 70% of respective lengths s(u,v), represented by the series: f(1,1),f(1,2) . . . f(1,v) . . . f(1,v),f(2,1),f(2,2) . . . f(2,v) . . . f(2,V) . . . f(u,1) . . . f(U,V), wherein s(u,v) is an integer multiple of a preselected length d(v) defining a recurring refractive index modulation of said subfilter elements; and wherein said subfilter elements comprise a series of overlapping optical cavities C(u,v) of length L(u,v), each respective said optical cavity length being substantially equal to the inverse average refractive index thereof times an integer m number of preselected half wavelengths to be reflected by said filter, L(u,v)=mλ m (u,v)/2n a (u,v), and where m is at least 5, and, wherein the lengths s(u,v)=M(u,v)d(v) and the amplitude of the modulation of the refractive index of the filter elements f(u,v) contained by the cavities C(u,v) are preselected to provide a preselected amplitude modulation of the reflectance of said wavelengths to be reflected by the combined coherent interference of the said cavities.
Claim 2
Dependent Claim
236 words
A comb type optical interference filter comprising: (a) a first plurality of layers f(u,v), u=1 to U, v=1 to V defining a second plurality of individual optical cavities C(u,v) of length L(u,v), u=1 to U, v=1 to V, where U and V are preselected integers and U not less than 2, each said optical cavity comprising a third plurality of subfilter elements f(u,v) each having a reflectance at most equal to 70% of respective lengths s(u,v), represented by the series: f(1,1),f(1,2) . . . f(1,v) . . . f(1,v),f(2,1),f(2,2) . . . f(2,v) . . . f(2,V) . . . f(u,1) . . . f(U,V), wherein s(u,v) is an integer multiple of a preselected length d(v) defining a recurring refractive index modulation of said subfilter elements; and wherein said subfilter elements comprise a series of overlapping optical cavities C(u,v) of length L(u,v), each respective said optical cavity length being substantially equal to the inverse average refractive index thereof times an integer m number of preselected half wavelengths to be reflected by said filter, L(u,v)=mλ m (u,v)/2n a (u,v), and where m is at least 5, and, wherein the lengths s(u,v)=M(u,v)d(v) and the amplitude of the modulation of the refractive index of the filter elements f(u,v) contained by the cavities C(u,v) are preselected to provide a preselected amplitude modulation of the reflectance of said wavelengths to be reflected by the combined coherent interference of the said cavities.
Claim 3
Dependent Claim
13 words
The filter of claim 1 wherein said filter elements f(u,v) comprise a dielectric.
Claim 4
Dependent Claim
42 words
The filter of claim 2 wherein said dielectric is selected from a group consisting of TiO 2 , germanium, silicon, BaTiO 3 , LiNbO 3 , Ba.sub..25 Sr.sub..75 Nb 2 O 6 , ZnO, 2-methyl-4-nitroaniline, liquid crystal composite, polystyrine/collodion, and polystyrene/polyvinyl alcohol.
Claim 5
Dependent Claim
14 words
The filter of claim 1 wherein the filter elements f(u,v) comprise an electro-optic material.
Claim 6
Dependent Claim
15 words
The filter of claim 1 wherein the filter elements f(u,v) comprise an elastically deformable material.
Claim 7
Dependent Claim
19 words
The filter of claim 1 wherein at least one of the L(u,v) is an integer multiple of another L(u,v).
Claim 8
Dependent Claim
10 words
The filter of claim 1 wherein all L(u,v) are equal.
Claim 9
Dependent Claim
14 words
The filter of claim 1 wherein s(u,v) equals s(v) for all values of u.
Claim 10
Dependent Claim
15 words
The filter of claim 1 wherein all s(u,v) are integer multiples of a common length.
Claim 11
Dependent Claim
10 words
The filter of claim 9 wherein all s(u,v) are equal.
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