US3720882A
Expired / Lapsed
US
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Parametric frequency conversion
Assignee: Research Corp
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Filing: 1970-08-03
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Granted: 1973-03-13
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Expires: 1990-08-03
Abstract
Abstract Parametric frequency conversion is effected in a sample of material, such as an alkali vapor, having an energy level system including first and second energy levels with a first transition frequency between them, and a third energy level with a second transition frequency between the third level and one of the first and second levels. The sample of material is disposed in a resonant structure resonating at a frequency substantially equal to the first transition frequency, so as to be within an oscillating electromagnetic field of frequency substantially equal to the first transition frequency, established and maintained by application of a signal to the resonant structure. With a population imbalance between the first and second levels established in the sample as by optical pumping, a carrier beam of energy at a frequency substantially equal to the second transition frequency is directed through the sample. The resonant structure is designed to provide a wavelength within the structure for the field frequency that satisfies a phase-matching condition such that sidebands of the carrier beam are produced by modulation of the index of refraction of the sample, these sidebands differing from the carrier frequency by integral multiples of the field frequency. By appropriate polarizing means, the generated sidebands can be detected, or alternatively, a polarized component of the carrier beam modulated in intensity at the field frequency can be detected. Devices providing this parametric frequency conversion may be arranged to operate as stable, self-oscillating frequency standards or for other purposes such as microwave photon detection.
Inventors
- 👤 W Happer
- 👤 H Tang
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 15:17
CPC Classifications
G; G04; G04F; G04F5/00; G04F5/14; G02; G02F; G02F1/00; G02F1/35; G02F1/39
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
226 words
A frequency-converting device including a. a sample of material having an energy level system including first and second levels with a transition frequency omega 12 between said first and second levels and a third level with a transition frequency omega 13 between said third level and one of said first and second levels; b. means for propagating electromagnetic energy of frequency Nu substantially equal to frequency omega 13 along an extended path through said sample; and c. means for establishing and maintaining a resonant oscillating electromagnetic field of frequency Omega substantially equal to frequency omega 12 for inducing transitions between said first and second levels in said sample and thereby modulating the index of refraction of said sample, said fieldestablishing and maintaining means including a resonant structure, said sample being disposed within the field of said structure, said structure resonating at a frequency substantially equal to frequency omega 12 and providing a wavelength Lambda within the structure for energy of said last-mentioned frequency; wherein the improvement comprises: d. said resonant structure including means for providing phasematching between said oscillating field and energy of frequency Nu propagating along said path; and e. said sample of material and said means for propagating energy of frequency Nu being mutually disposed and adapted such that said path through said sample in said field has a length greater than Lambda .
Claim 2
Dependent Claim
226 words
A frequency-converting device including a. a sample of material having an energy level system including first and second levels with a transition frequency omega 12 between said first and second levels and a third level with a transition frequency omega 13 between said third level and one of said first and second levels; b. means for propagating electromagnetic energy of frequency Nu substantially equal to frequency omega 13 along an extended path through said sample; and c. means for establishing and maintaining a resonant oscillating electromagnetic field of frequency Omega substantially equal to frequency omega 12 for inducing transitions between said first and second levels in said sample and thereby modulating the index of refraction of said sample, said fieldestablishing and maintaining means including a resonant structure, said sample being disposed within the field of said structure, said structure resonating at a frequency substantially equal to frequency omega 12 and providing a wavelength Lambda within the structure for energy of said last-mentioned frequency; wherein the improvement comprises: d. said resonant structure including means for providing phasematching between said oscillating field and energy of frequency Nu propagating along said path; and e. said sample of material and said means for propagating energy of frequency Nu being mutually disposed and adapted such that said path through said sample in said field has a length greater than Lambda .
Claim 3
Dependent Claim
226 words
A frequency-converting device including a. a sample of material having an energy level system including first and second levels with a transition frequency omega 12 between said first and second levels and a third level with a transition frequency omega 13 between said third level and one of said first and second levels; b. means for propagating electromagnetic energy of frequency Nu substantially equal to frequency omega 13 along an extended path through said sample; and c. means for establishing and maintaining a resonant oscillating electromagnetic field of frequency Omega substantially equal to frequency omega 12 for inducing transitions between said first and second levels in said sample and thereby modulating the index of refraction of said sample, said field-establishing and maintaining means including a resonant structure, said sample being disposed within the field of said structure, said structure resonating at a frequency substantially equal to frequency omega 12 and providing a wavelength Lambda within the structure for energy of said last-mentioned frequency; wherein the improvement comprises: d. said resonant structure including means for providing phase-matching between said oscillating field and energy of frequency Nu propagating along said path; and e. said sample of material and said means for propagating energy of frequency Nu being mutually disposed and adapted such that said path through said sample in said field has a length greater than Lambda .
Claim 4
Dependent Claim
226 words
A frequency-converting device including a. a sample of material having an energy level system including first and second levels with a transition frequency omega 12 between said first and second levels and a third level with a transition frequency omega 13 between said third level and one of said first and second levels; b. means for propagating electromagnetic energy of frequency Nu substantially equal to frequency omega 13 along an extended path through said sample; and c. means for establishing and maintaining a resonant oscillating electromagnetic field of frequency Omega substantially equal to frequency omega 12 for inducing transitions between said first and second levels in said sample and thereby modulating the index of refraction of said sample, said field-establishing and maintaining means including a resonant structure, said sample being disposed within the field of said structure, said structure resonating at a frequency substantially equal to frequency omega 12 and providing a wavelength Lambda within the structure for energy of said last-mentioned frequency; wherein the improvement comprises: d. said resonant structure including means for providing phase-matching between said oscillating field and energy of frequency Nu propagating along said path; and e. said sample of material and said means for propagating energy of frequency Nu being mutually disposed and adapted such that said path through said sample in said field has a length greater than Lambda .
Claim 5
Dependent Claim
27 words
A device as defined in claim 1, including means for establishing and maintaining a population imbalance between said first and second levels in said sample of material.
Claim 6
Dependent Claim
54 words
A device as defined in claim 1, wherein said frequency Nu is sufficiently close to said frequency omega 13 to be modulated by resonance of said material at said frequency omega 12 and sufficiently different from said frequency omega 13 so that the energy of frequency Nu is not substantially absorbed by said material.
Claim 7
Dependent Claim
38 words
A device as defined in claim 3, including means for selectively detecting a circularly polarized component of said energy of frequency Nu after passage thereof through said sample of material to detect modulation in intensity of said component.
Claim 8
Dependent Claim
46 words
A device as defined in claim 3, including first and second linear polarizing elements respectively disposed on opposite sides of said sample of material in the propagation path of said energy of frequency Nu , said polarizing elements being disposed orthogonally with respect to each other.
Claim 9
Dependent Claim
86 words
A device as defined in claim 1, wherein said material is an atomic vapor, said first and second levels are hyperfine levels, said transition frequency omega 12 is a microwave frequency, and said transition frequency omega 13 is an optical frequency; wherein absorption of energy of said frequency omega 13 by said vapor effects population imbalance between said hyperfine levels; and including means for pumping said vapor with optical energy of said frequency omega 13 to produce a population imbalance between said hyperfine levels as aforesaid.
Claim 10
Dependent Claim
40 words
A device as defined in claim 6, wherein said resonant structure is a microwave cavity resonating at a frequency substantially equal to omega 12, and further including means for applying a microwave signal of said frequency Omega to said cavity.
Claim 11
Dependent Claim
123 words
A device as defined in claim 7, wherein said atomic vapor is contained within an elongated envelope disposed within said cavity; said means for propagating energy of frequency Nu is disposed and adapted to direct a beam of said energy along a path extending longitudinally through said envelope; said cavity comprises a plurality of plates of conductive Material having aligned central openings and disposed in spaced array along said last-mentioned path with the major surfaces of said plates extending transversely of said path; and said pumping means comprises means disposed externally of said cavity for directing pumping energy into said envelope, transversely of said path, through the spaces between said plates over at least a major portion of the length of said envelope.
Claim 12
Dependent Claim
33 words
A device as defined in claim 8, wherein said envelope comprises a body of dielectric material dimensioned to dielectrically load said cavity for reducing the guide wavelength thereof to the value Lambda .
Claim 13
Dependent Claim
14 words
A device as defined in claim 7, wherein said vapor is an alkali vapor.
Claim 14
Dependent Claim
14 words
A device as defined in claim 10, wherein said vapor is rubidium 87 vapor.
Claim 15
Dependent Claim
32 words
A device as defined in claim 11, wherein said pumping means comprises a first rubidium 85 lamp, and said means for propagating energy of frequency Nu comprises a second rubidium 85 lamp.
Claim 16
Dependent Claim
84 words
A device as defined in claim 12, including means for selectively detecting a circularly polarized component of said beam after passage thereof through said vapor, said component being modulated in intensity at a microwave frequency substantially equal to omega 12, and wherein said means for applying a microwave signal to said cavity comprises means for deriving from said circularly polarized component of said beam a microwave signal at the frequency of modulation of said component and feeding said last-mentioned signal back to said cavity.
Claim 17
Dependent Claim
14 words
A device as defined in claim 10, wherein said vapor is rubidium 85 vapor.
References Cited (Backward Citations)
US3513381A
Cited
US3493894A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-03-12 | 1976-09-11 | 1977-03-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-03-12 | 1980-09-11 | 1981-03-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-03-12 | 1984-09-11 | 1985-03-13 | $7700.00 | Window Closed / Lapsed |