US3883221A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Portable prism-grating coupler
Assignee: AT&T Inc
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Filing: 1974-02-01
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Granted: 1975-05-13
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Expires: 1994-02-01
Abstract
Abstract There is disclosed a portable, reusable prism coupler which, unlike conventional prism couplers, need not be of higher refractive index than that of the thin-film waveguide into which the light is to be introduced. Structurally, there is fabricated on the surface of the prism which is disposed nearest to the thin-film waveguide a fixed optical grating. Grating periodicity is selected such that a beam of light incident on the grating inside the prism is internally diffracted essentially completely in a backward direction. By properly selecting the angle of incidence of the light beam on the grating, the evanescent field of the diffracted portion of the beam can be phase-matched and coupled through the separation between the prism and the waveguide to the various propagating modes therein. Since the refractive index of the prism is essentially uncritical, the arrangement should be particularly useful for coupling light into and out of thin-film waveguides formed of materials having relatively high refractive indices (e.g., gallium arsenide). The arrangement may likewise be useful for the large scale, nondestructive testing of thin-film waveguides as they are fabricated on the production line.
Inventors
- 👤 William Walter Rigrod
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 06:13
CPC Classifications
G; G02; G02B; G02B6/00; G02B6/24; G02B6/26; G02B6/34
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
165 words
An optical coupling arrangement of the type comprising a body of optically transparent material having an index of refraction nf and two opposing major surfaces separated by a distance proportioned for guiding a beam of optical electromagnetic radiation, and a prism of optically transparent material having an index of refraction np, said prism having a surface disposed essentially parallel to and separated by a gap of index of refraction no from one of the major surfaces of said body, no being smaller in value than nf and np, respectively, said arrangement being characterized in that said surface of said prism includes a fixed optical grating having a grating periodicity selected for diffracting at least a portion of the beam of optical radiation incident thereon inside said prism, said surface of said prism being oriented to receive said beam at an angle providing coupling through said gap between the evanescent field of a diffracted portion of said beam and a propagating waveguide mode in said body.
Claim 2
Dependent Claim
165 words
An optical coupling arrangement of the type comprising a body of optically transparent material having an index of refraction nf and two opposing major surfaces separated by a distance proportioned for guiding a beam of optical electromagnetic radiation, and a prism of optically transparent material having an index of refraction np, said prism having a surface disposed essentially parallel to and separated by a gap of index of refraction no from one of the major surfaces of said body, no being smaller in value than nf and np, respectively, said arrangement being characterized in that said surface of said prism includes a fixed optical grating having a grating periodicity selected for diffracting at least a portion of the beam of optical radiation incident thereon inside said prism, said surface of said prism being oriented to receive said beam at an angle providing coupling through said gap between the evanescent field of a diffracted portion of said beam and a propagating waveguide mode in said body.
Claim 3
Dependent Claim
34 words
The coupling arrangement of claim 1 in which the index Of refraction nf of said body has a value at least as large as that of the index of refraction np of said prism.
Claim 4
Dependent Claim
70 words
The coupling arrangement of claim 1 for use as an input coupler including a source of said beam of optical radiation, means for directing the incidence of said beam on said grating, and in which said body comprises a thin waveguiding film having a thickness of the order of the wavelength of said beam, said gap between said prism and said body being less than the wavelength of said beam.
Claim 5
Dependent Claim
48 words
The coupling arrangement of claim 3 in which said grating comprises a spatially periodic variation in the height of said prism surface having a periodicity Lambda selected for diffracting said portion of said beam essentially in a backward direction relative to the direction of incidence of said beam.
Claim 6
Dependent Claim
28 words
The coupling arrangement of claim 4 in which said beam is directed at an angle theta p to the normal to said prism surface such that the relationship
Claim 7
Dependent Claim
25 words
The coupling arrangement of claim 5 in which the periodicity Lambda of said grating and the angle theta p are selected such that the relationship
Claim 8
Dependent Claim
43 words
The coupling arrangement of claim 5 in which said source is a neodymium ion laser providing said beam of approximately 1.06 micrometers in wavelength and in which the material of said prism and of said thin waveguiding film consists essentially of gallium arsenide.
Claim 9
Dependent Claim
49 words
The coupling arrangement of claim 1 in which said surface of said prism is coated with a layer of transparent protective cladding material having a relatively flat exterior surface as compared to said prism surface and an index of refraction nc which is less than np and nf, respectively.
Claim 10
Dependent Claim
16 words
The coupling arrangement of claim 8 in which said protective cladding is a flexible polymer material.
Claim 11
Dependent Claim
25 words
The coupling arrangement of claim 8 in which said prism consists essentially of gallium arsenide and said protective cladding consists essentially of aluminum gallium arsenide.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-05-12 | 1978-11-11 | 1979-05-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-05-12 | 1982-11-11 | 1983-05-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-05-12 | 1986-11-11 | 1987-05-13 | $7700.00 | Window Closed / Lapsed |