US4255017A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Tunable source of coherent electromagnetic radiation based on modulational instability
Assignee: AT&T Inc
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Filing: 1979-12-14
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Granted: 1981-03-10
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Expires: 1999-12-14
Abstract
Abstract Method for achieving phase matching for electromagnetic radiation propagating through single mode transmission media, such as, for instance, single mode optical fiber. When coherent, monochromatic radiation of essentially constant amplitude, the carrier, is propagating through such a medium, and if the frequency of the carrier is chosen to be within a region of anomalous dispersion of the medium, then, provided the medium has a finite nonlinear coefficient of the index of refraction, the carrier wave is subject to a modulational instability. This instability results in the generation and exponential growth of sidebands, the two closest to the carrrier frequency being the dominant ones. The modulation frequency is proportional to the square root of the power in the carrier wave. Apparatus for using the method is also disclosed, such as apparatus for using the method to tunably generate coherent radiation in the far infrared, apparatus for tunably generating coherent radiation relatively close to the carrier frequency, and apparatus for using the method for amplifying radiation at a frequency relatively close to the carrier frequency.
Inventors
- 👤 Akira Hasegawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 03:28
CPC Classifications
G; G02; G02F; G02F1/00; G02F1/35; G02F1/353; G02F1/3534; H; H04; H04B; H04B10/00; H04B10/50; H04B10/501; H04B10/503
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
105 words
A method for generating coherent electromagnetic radiation comprising: (a) coupling essentially constant amplitude, coherent electromagnetic radiation at a first frequency into a single mode transmission medium adapted to transmit radiation at the first frequency, the medium having at least one frequency region of anomalous dispersion, and (b) separating electromagnetic radiation at a second frequency different from the first frequency from the radiation after the radiation has propagated through the transmission medium, CHARACTERIZED IN THAT the carrier frequency is chosen to lie within the region of anomalous dispersion of the transmission medium, thereby achieving efficient generation of coherent electromagnetic radiation at least at the second frequency.
Claim 2
Independent Claim
105 words
A method for generating coherent electromagnetic radiation comprising: (a) coupling essentially constant amplitude, coherent electromagnetic radiation at a first frequency into a single mode transmission medium adapted to transmit radiation at the first frequency, the medium having at least one frequency region of anomalous dispersion, and (b) separating electromagnetic radiation at a second frequency different from the first frequency from the radiation after the radiation has propagated through the transmission medium, CHARACTERIZED IN THAT the carrier frequency is chosen to lie within the region of anomalous dispersion of the transmission medium, thereby achieving efficient generation of coherent electromagnetic radiation at least at the second frequency.
Claim 3
Dependent Claim
19 words
The method according to claim 1 wherein the single mode transmission medium is a waveguide containing SiO 2 .
Claim 4
Dependent Claim
40 words
The method according to claim 1 wherein coherent electromagnetic radiation at a third frequency is coupled into the transmission medium, together with the radiation at the first frequency, with the third frequency being essentially the same as the second frequency.
Claim 5
Dependent Claim
194 words
Apparatus for generating at least two narrow bands of substantially coherent electromagnetic radiation having center frequencies ν o ±ν m , comprising (a) a source for producing substantially monochromatic coherent electromagnetic radiation, the carrier wave, having substantially constant amplitude |E o |, frequency ν o , and wave number k o , (b) a single mode waveguide comprising material adapted to transmit radiation of frequency ν o , the material having at the frequency ν o a linear refractive index n o , and a nonlinear coefficient of the index of refraction n 2 , the material having at least one region of anomalous dispersion, and (c) means for coupling the carrier into the waveguide, CHARACTERIZED IN THAT (d) the carrier frequency ν o is chosen to lie within the at least one region of anomalous dispersion of the material of the waveguide, and (e) the input amplitude of the carrier |E o | is maintained so as to satisfy the relationship ##EQU4## wherein v.sub.g is the group velocity, δv.sub.g ν/δνv.sub.g is the normalized group dispersion, both evaluated at ν o , resulting in at least sidebands of frequency ν o ±ν m .
Claim 6
Dependent Claim
194 words
Apparatus for generating at least two narrow bands of substantially coherent electromagnetic radiation having center frequencies ν o ±ν m , comprising (a) a source for producing substantially monochromatic coherent electromagnetic radiation, the carrier wave, having substantially constant amplitude |E o |, frequency ν o , and wave number k o , (b) a single mode waveguide comprising material adapted to transmit radiation of frequency ν o , the material having at the frequency ν o a linear refractive index n o , and a nonlinear coefficient of the index of refraction n 2 , the material having at least one region of anomalous dispersion, and (c) means for coupling the carrier into the waveguide, CHARACTERIZED IN THAT (d) the carrier frequency ν o is chosen to lie within the at least one region of anomalous dispersion of the material of the waveguide, and (e) the input amplitude of the carrier |E o | is maintained so as to satisfy the relationship ##EQU4## wherein v.sub.g is the group velocity, δv.sub.g ν/δνv.sub.g is the normalized group dispersion, both evaluated at ν o , resulting in at least sidebands of frequency ν o ±ν m .
Claim 7
Dependent Claim
30 words
Apparatus according to claim 4, further comprising means for separating at least partially the electromagnetic energy contained in at least one of the sidebands from the output of the waveguide.
Claim 8
Dependent Claim
14 words
Apparatus according to claim 4 wherein the carrier wave is derived from a laser.
Claim 9
Dependent Claim
11 words
Apparatus accordingg to claim 6 wherein the laser is amplitude stabilized.
Claim 10
Dependent Claim
13 words
Apparatus according to claim 4 wherein the waveguide substantially consists of optical fiber.
Claim 11
Dependent Claim
13 words
Apparatus according to claim 8 wherein the optical fiber contains SiO 2 .
Claim 12
Dependent Claim
33 words
Apparatus according to claim 5 wherein the energy contained in at least one sideband is at least partially separated from the output of the waveguide by means of a diode rectifier and filters.
Claim 13
Dependent Claim
32 words
Apparatus according to claim 5 wherein the energy contained in at least one sideband is at least partially separated from the output of the waveguide by means of a mixer and filters.
Claim 14
Dependent Claim
31 words
Apparatus according to claim 4 wherein modulating means are used to modulate the carrier wave at the modulation frequency ν m prior to coupling the modulated carrier wave into the waveguide.
Claim 15
Dependent Claim
33 words
Apparatus according to claim 5 wherein the energy contained in at least one of the sidebands is at least partially separated from the output of the waveguide by means of an optical cavity.
References Cited (Backward Citations)
US4095122A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-03-09 | 1984-09-08 | 1985-03-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-03-09 | 1988-09-08 | 1989-03-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-03-09 | 1992-09-08 | 1993-03-10 | $7700.00 | Window Closed / Lapsed |