US3586997A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Stabilized mode-locked laser arrangement
Assignee: AT&T Inc
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Filing: 1969-05-26
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Granted: 1971-06-22
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Expires: 1989-05-26
Abstract
Abstract It has been observed that the pulse-train output of a modelocked Nd:YA1G laser exhibits a 180* phase instability. As a result it is not possible to achieve long term stable operation of such a laser by abstracting from the output pulse train a signal whose frequency corresponds to the axial-mode fundamental beat frequency. However, the phase of the second harmonic of this fundamental beat frequency which may be abstracted from the output pulse train does not exhibit such a 180* phase instability. Accordingly this second harmonic signal can be utilized as a discriminant from which a fundamental signal may be derived. In turn this derived fundamental signal is applied to drive an intracavity phase modulator. In this way the laser is stabilized in its mode-locked state by feedback techniques despite the aforementioned phase-instability characteristic.
Inventors
- 👤 Tracy S Kinsel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 07:51
CPC Classifications
H; H01; H01S; H01S3/00; H01S3/10; H01S3/11; H01S3/1106; H01S3/1109; H01S3/13; H01S3/136; H01S3/1305
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
75 words
A combination as in claim 1 further including voltage-controlled oscillator means for applying a modulating signal to said modulator, and a phase-sensitive detector responsive to the output of said oscillator means and to said signal at or near the average mode-spacing frequency for applying a correction signal to said oscillator means to maintain the output of said laser and the output of said oscillator means in synchronism thereby to achieve mode-locked operation of said laser.
Claim 2
Dependent Claim
83 words
A combination as in claim 1 further including means for controlling the length of said cavity, single-frequency oscillator means for applying a modulating signal to said modulator, and a phase-sensitive detector responsive to the output of said oscillator means and to said signal at or near the average mode-spacing frequency for applying a correction signal to said controlling means to maintain the output of said laser and the output of said oscillator means in synchronism thereby to achieve mode-locked operation of said laser.
Claim 3
Dependent Claim
151 words
In combination in a mode-locked multiaxial-mode laser arrangement whose output waveform is characterized by a phase-instability phenomenon, a laser cavity having a main axis, a laser element and a phase modulator both positioned within said cavity along said axis, and a feedback circuit extending between said cavity and said modulator, said circuit comprising means for extracting from said cavity a second-harmonic signal at twice the frequency that corresponds to the average spacing between the multiple modes capable of being propagated in said cavity, means responsive to said extracting means for providing a signal, at the average mode-spacing frequency, which does not exhibit said phase instability, means for shifting the phase of said signal at the average mode-spacing frequency by a predetermined amount, and means responsive to said phase-shifted signal at the average mode-spacing frequency for driving said modulator at the average mode-spacing frequency to achieve stable mode-locked operation of said arrangement.
Claim 4
Dependent Claim
39 words
A combination as in claim 4 wherein said cavity comprises a partially transmissive member for propagating an optical signal outside said cavity, and wherein said extracting means comprises a photodector disposed to receive the signal transmitted through said member.
Claim 5
Dependent Claim
27 words
A combination as in claim 5 wherein said extracting means further includes a filter connected to the output of said photodetector for passing only said second-harmonic signal.
Claim 6
Dependent Claim
22 words
A combination as in claim 6 wherein said providing means comprises a divide-frequency-by-two synchronized oscillator connected to the output of said filter.
Claim 7
Dependent Claim
37 words
A combination as in claim 7 wherein said shifting means comprises a phase-shifting network connected to the output of said oscillator for adjusting the total phase shift in said feedback circuit to a multiple of 360* .
Claim 8
Dependent Claim
25 words
A combination as in claim 8 wherein said driving means comprises a direct electrical connection between said modulator and the output of said phase-shifting network.
Claim 9
Dependent Claim
81 words
A combination as in claim 8 wherein said driving means comprises a two-input phase-sensitive detector having one input thereof connected to the output of said phase-shifting network, a voltage-controlled oscillator unit adapted to provide an output signal at said average mode-spacing frequency and a coupler responsive to the output signal of said unit for applying a portion of said output signal to the other input of said phase-sensitive detector and for applying the remainder of said output signal to said modulator.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-06-21 | 1974-12-21 | 1975-06-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-06-21 | 1978-12-21 | 1979-06-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-06-21 | 1982-12-21 | 1983-06-22 | $7700.00 | Window Closed / Lapsed |