US4807970A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Holograms in photorefractive materials
Assignee: International Business Machines Corp
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Filing: 1987-11-23
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Granted: 1989-02-28
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Expires: 2007-11-23
Abstract
Abstract The holographic diffraction efficiencies of photorefractive or electro-optic crystals, such as bismuth silicon oxide (BSO), increase while experiencing high AC voltages. The diffraction efficiency also increases with frequency of the AC voltages up to a saturation frequency. These enhancements are attributed to the response times of the crystal and the superposition of internal electric fields. The enhanced diffraction efficiency assists in retentively recording information bearing holograms in electro-optic crystalline media.
Inventors
- 👤 Roger R. Dube
- 👤 Shingshwang Yao
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 14:21
CPC Classifications
G; G03; G03H; G03H1/00; G03H1/02; G03H1/024; G03H1/0248; G02; G02F; G02F1/00; G02F1/01; G02F1/03; G02F1/05; G02F1/0541; G11; G11C; G11C13/00; G11C13/04; G11C13/042; Y; Y10; Y10S; Y10S359/00; Y10S359/90
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
138 words
In a method of optically activating a photorefractive crystal medium having a 110 axis; the steps of: subjecting the medium to an alternating polarity bias electric field along its 110 axis having a frequency of not greater than about one-hundred Hertz; shining two beams of monochromatic light on the medium so that impingement of the two beams on the medium is transverse to the 110 axis; maintaining the intensities of the two light beams to be within a ratio of less than 1000 to 1 in relative light intensities; modulating one of the light beam intensities with information to be inserted into the medium in volume holographic form by interaction of the two light beams within the medium; and maintaining the bias electric field such that diffraction efficiency is maximized at the bias frequency and said intensity ratio.
Claim 2
Dependent Claim
138 words
In a method of optically activating a photorefractive crystal medium having a 110 axis; the steps of: subjecting the medium to an alternating polarity bias electric field along its 110 axis having a frequency of not greater than about one-hundred Hertz; shining two beams of monochromatic light on the medium so that impingement of the two beams on the medium is transverse to the 110 axis; maintaining the intensities of the two light beams to be within a ratio of less than 1000 to 1 in relative light intensities; modulating one of the light beam intensities with information to be inserted into the medium in volume holographic form by interaction of the two light beams within the medium; and maintaining the bias electric field such that diffraction efficiency is maximized at the bias frequency and said intensity ratio.
Claim 3
Dependent Claim
26 words
In the method set forth in claim 1, in said maintaining step; maintaining the intensity ratios of the light beams to be about one to one.
Claim 4
Dependent Claim
22 words
In the method set forth in claim 1, further including the step of: selecting said photorefractive crystal to be bismuth silicon oxide.
Claim 5
Dependent Claim
16 words
A hologram containing article having a hologram induced by the steps set forth in claim 1.
Claim 6
Dependent Claim
88 words
In a method of retentively photoinducing a hologram into a photorefractive crystalline medium; the steps of: subjecting the medium to an AC electric field having a frequency of about 100 Hertz; impinging a beam of constant frequency radiant energy onto the medium over an area of the medium which is to store a hologram; impinging an information-carrying light beam of radiant energy onto said receiving area of said medium; and keeping the energy intensities of said beams of radiant energy to a ratio of not greater than 1:1000.
Claim 7
Dependent Claim
88 words
In a method of retentively photoinducing a hologram into a photorefractive crystalline medium; the steps of: subjecting the medium to an AC electric field having a frequency of about 100 Hertz; impinging a beam of constant frequency radiant energy onto the medium over an area of the medium which is to store a hologram; impinging an information-carrying light beam of radiant energy onto said receiving area of said medium; and keeping the energy intensities of said beams of radiant energy to a ratio of not greater than 1:1000.
Claim 8
Dependent Claim
18 words
In the method set forth in claim 5, further including: selecting said medium to be bismuth silicon oxide.
Claim 9
Dependent Claim
15 words
An article including a hologram induced by the method steps set forth in claim 5.
Claim 10
Dependent Claim
77 words
In a method of recording a hologram in an electro optic crystalline record medium having a radiant-energy receiving surface for receiving hologram-inducing, radiant-energy beams; including the steps of: inducing in said medium, at least in a portion of the medium which is to store a hologram, an electric field varying at a frequency of not greater than about 100 Hertz; and impinging a plurality of substantially identical light intensity hologram inducing radiant-energy beams onto said receiving surface.
Claim 11
Dependent Claim
77 words
In a method of recording a hologram in an electro optic crystalline record medium having a radiant-energy receiving surface for receiving hologram-inducing, radiant-energy beams; including the steps of: inducing in said medium, at least in a portion of the medium which is to store a hologram, an electric field varying at a frequency of not greater than about 100 Hertz; and impinging a plurality of substantially identical light intensity hologram inducing radiant-energy beams onto said receiving surface.
Claim 12
Dependent Claim
14 words
An article having a hologram induced therein using the method steps of claim 8.
Claim 13
Dependent Claim
103 words
In data storage apparatus, including, in combination: a photorefractive crystal having a 110 axis; low-frequency bias means connected to said crystal for inducing a low-frequency bias field of about 100 Hertz in the crystal along said 110 axis; light means optically coupled to said crystal for emitting a light beam to be intercepted by the crystal, said light beams supplying two light beams of substantially equal light intensities to said crystal; and modulation means operatively coupled to the light means for activating the light means to modulate light intensity thereof to impose information on the light beam to be stored in said crystal.
Claim 14
Dependent Claim
103 words
In data storage apparatus, including, in combination: a photorefractive crystal having a 110 axis; low-frequency bias means connected to said crystal for inducing a low-frequency bias field of about 100 Hertz in the crystal along said 110 axis; light means optically coupled to said crystal for emitting a light beam to be intercepted by the crystal, said light beams supplying two light beams of substantially equal light intensities to said crystal; and modulation means operatively coupled to the light means for activating the light means to modulate light intensity thereof to impose information on the light beam to be stored in said crystal.
References Cited (Backward Citations)
US4674824A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1992-02-28 | 1992-08-29 | 1993-02-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-02-28 | 1996-08-29 | 1997-02-28 | $3760.00 | Window Closed / Lapsed |
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