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US3622912A
Expired / Lapsed
US
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Intra-cavity polarization modulated laser
Assignee: Lanteris Space LLC
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Filing: 1969-05-22
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Granted: 1971-11-23
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Expires: 1989-05-22
Abstract
Abstract A laser polarization modulation system including within the laser cavity and in the laser light path a gaseous discharge tube adapted to produce laser oscillations in any one of a number of polarizations, a weakly birefringent element, and a modulator element the birefringence of which is variable, in response to an applied signal, up to a maximum value substantially greater than that of the weakly birefringent element. The modulator element is so oriented with respect to the weakly birefringent element that the modulator element, when supplied with a signal, exhibits an optic axis, oriented plus or minus 45* with respect to the optic axis of the weakly birefringent element, the sign of the angle of orientation depending on the polarity of the applied signal. The amount of birefringence exhibited by the modulator element depends directly on the value of the signal applied thereto. When no signal is applied to the modulator element, it exhibits no birefringence, and the weakly birefringent element is effective to constrain laser oscillations to a single polarization either perpendicular to or parallel to its optic axis. When an applied signal causes the modulator element to exhibit birefringence, that element causes the polarization of the laser oscillations to rotate toward the optic axis of the modulator element by an amount directly dependent on the value of the applied signal. The polarization-modulated output of the laser can be converted into an amplitude modulated signal by passing the laser output through a linear polarizer located externally of the laser cavity. Because only a small change in the birefringence of the modulator element is needed to effect substantially 100 percent amplitude modulation, the frequency of the laser oscillations is not shifted significantly by this change.
Inventors
- 👤 Walter M Doyle
- 👤 Matthew B White
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 19:22
CPC Classifications
H; H01; H01S; H01S3/00; H01S3/10; H01S3/106; H01S3/107
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
296 words
A laser system comprising: a plurality of reflecting means, positioned to define a closed optical path; means including an active medium, positioned between a pair of said reflecting means and having a longitudinal axis substantially coincident with said optical path, for producing, when pumped, coherent light having (i) any one of a plurality of linear polarizations, when no birefringent material intercepts said optical path, and (ii) a single linear polarization, when a birefringent material having its optic axis perpendicular to said optical path intercepts said path, the direction of said single linear polarization being dependent on the direction of said optic axis of said birefringent material; means for pumping said active medium; signal-responsive birefringent means (i) disposed in said optical path, (ii) having in the absence of an applied signal a weak birefringence and an optic axis oriented in a first fixed direction substantially perpendicular to said optical path, (iii) responsive to an applied signal to produce an effective optic axis oriented substantially perpendicular to said optical path in a direction displaced from said first fixed direction by an amount dependent on the value of said applied signal, and (iv) transmissive in both directions, along the portion of said optical path intercepted by said birefringent means, of radiation polarized in any direction; the combination of said reflecting means, said means including said active medium, said pumping means and said birefringent means forming an oscillatory system having maximum gain for coherent radiation plane-polarized in one particular direction dependent on said direction of said effective optic axis, whereby said active medium, when pumped, radiates, and said oscillatory system selectively generates, coherent radiation polarized in said one particular direction; and means for obtaining outside said closed optical path a portion of said coherent radiation generated within said closed path.
Claim 2
Dependent Claim
296 words
A laser system comprising: a plurality of reflecting means, positioned to define a closed optical path; means including an active medium, positioned between a pair of said reflecting means and having a longitudinal axis substantially coincident with said optical path, for producing, when pumped, coherent light having (i) any one of a plurality of linear polarizations, when no birefringent material intercepts said optical path, and (ii) a single linear polarization, when a birefringent material having its optic axis perpendicular to said optical path intercepts said path, the direction of said single linear polarization being dependent on the direction of said optic axis of said birefringent material; means for pumping said active medium; signal-responsive birefringent means (i) disposed in said optical path, (ii) having in the absence of an applied signal a weak birefringence and an optic axis oriented in a first fixed direction substantially perpendicular to said optical path, (iii) responsive to an applied signal to produce an effective optic axis oriented substantially perpendicular to said optical path in a direction displaced from said first fixed direction by an amount dependent on the value of said applied signal, and (iv) transmissive in both directions, along the portion of said optical path intercepted by said birefringent means, of radiation polarized in any direction; the combination of said reflecting means, said means including said active medium, said pumping means and said birefringent means forming an oscillatory system having maximum gain for coherent radiation plane-polarized in one particular direction dependent on said direction of said effective optic axis, whereby said active medium, when pumped, radiates, and said oscillatory system selectively generates, coherent radiation polarized in said one particular direction; and means for obtaining outside said closed optical path a portion of said coherent radiation generated within said closed path.
Claim 3
Dependent Claim
59 words
A laser system according to claim 1, wherein said birefringent means is responsive to the polarity of said applied signal to rotate said effective optic axis (i) in a given direction when said applied signal has a given polarity, and (ii) in a direction opposite said given direction when said applied signal has a polarity opposite said given polarity.
Claim 4
Dependent Claim
37 words
A laser system according to claim 1, said system additionally comprising means, located outside said closed optical path and positioned to intercept at least part of said obtained coherent radiation, for converting polarization-varying radiation into amplitude-varying radiation.
Claim 5
Dependent Claim
14 words
A laser system according to claim 1, wherein said active medium is carbon dioxide.
Claim 6
Dependent Claim
152 words
A system according to claim 1 wherein said laser system additionally comprises means for enclosing said active medium, said enclosing means comprising window means intersecting said optical path and substantially equally transmissive along said optical path, to and from said active medium, of light of every polarization, and wherein said birefringent means comprises a weakly birefringent element having a fixed optic axis oriented in said first fixed direction, and a modulator element the birefringence of which is variable, in response to an applied signal, up to a maximum value substantially greater than that of said weakly birefringent element, said modulator element being so oriented with respect to said weakly birefringent element that said modulator element, when supplied with a signal, exhibits an optic axis oriented in a given direction which is substantially perpendicular to said optical path and is at an acute angle to said optic axis of said weakly birefringent element.
Claim 7
Dependent Claim
47 words
A system according to claim 5 wherein said optic axis of said modulator element is oriented about plus or minus 45* with respect to said optic axis of said weakly birefringent element, the sign of the angle of orientation depending on the polarity of said applied signal.
Claim 8
Dependent Claim
27 words
A system according to claim 6 wherein the maximum birefringence of said modulator element is about 10 times greater than said birefringence of said weakly birefringent element.
Claim 9
Dependent Claim
26 words
A system according to claim 6 wherein said weakly birefringent element is a sheet of optical quality semiconductor material and said modulator is a Pockels cell.
Claim 10
Dependent Claim
27 words
A system according to claim 8 wherein said window means comprises windows made of an isotropic material and positioned approximately at right angles to said optical path.
Claim 11
Dependent Claim
89 words
A system according to claim 1 wherein said laser system additionally comprises means for enclosing said active medium, said enclosing means having windows intersecting said optical path and oriented approximately at right angles to said optical path, one of said windows having stress birefringence, and said birefringent means includes (i) said one window having stress birefringence and (ii) a modulator the birefringence of which is variable, in response to an applied signal, up to a maximum value substantially greater than that of said stress birefringence of said one window.
Claim 12
Dependent Claim
78 words
A system according to claim 1 wherein said active medium is enclosed in a discharge tube having windows approximately at right angles to said path and said birefringent means includes (i) means for applying a mechanical force to one of said windows to provide within said path a first birefringence and (ii) a modulator the birefringence of which is variable, in response to an applied signal, to a maximum value substantially greater than that of said first birefringence.
Claim 13
Dependent Claim
41 words
A laser system according to claim 1, wherein said means for obtaining a portion of said coherent radiation outside said closed path is comprised in one of said reflecting means, said one reflecting means being partially transmissive of said coherent radiation.
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) | 1974-11-22 | 1975-05-24 | 1975-11-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-11-22 | 1979-05-24 | 1979-11-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-11-22 | 1983-05-24 | 1983-11-23 | $7700.00 | Window Closed / Lapsed |