US5093833A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Optical pulse generator
Assignee: Massachusetts Institute of Technology
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Filing: 1991-02-15
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Granted: 1992-03-03
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Expires: 2011-02-15
Abstract
Abstract A fast rise time optical pulse generator is provided which utilizes a laser cavity having a gain medium with a pair of cavity arms extending therefrom, each cavity arm having a feedback element at its distal end. The gain medium has the property that if optical waves enter the gain medium from the two arms simultaneously, the gain is reduced. This will generally occur as a result of a gain saturation effect such as spatial hole burning. Since the gain reduction does not occur for pulses of a length equal to the length of the laser cavity or for odd submultiples of such pulses, outputs are obtained at one of these pulse lengths. Various means are provided for tuning the system to the desire harmonic.
Inventors
- 👤 L. Y. Pang
- 👤 Emily S. Kintzer
- 👤 James G. Fujimoto
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 18:06
CPC Classifications
H; H01; H01S; H01S5/00; H01S5/10; H01S5/14; H01S3/00; H01S3/05; H01S3/08; H01S3/10; H01S3/105; H01S3/106; H01S5/40; H01S5/4025; H01S5/4031
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
143 words
An optical pulse generator for pulses of a desired pulse width comprising a laser gain medium; a first cavity arm and a second cavity arm oriented relative to the gain medium and to each other so that a gain reduction effect persists in said gain medium when optical beams enter the gain medium from both arms simultaneously; optical feedback means in each cavity arm; and output coupling means in at least one of said cavity arms; the gain medium and the two cavity arms being further oriented to form a laser cavity having a length substantially equal to an odd multiple (h) of said pulse width, the relative lengths of said cavity arms being such that the gain medium is at a point in the laser cavity spaced from the center thereof by a multiple from zero to (h-1)/2 of said pulse width.
Claim 2
Dependent Claim
143 words
An optical pulse generator for pulses of a desired pulse width comprising a laser gain medium; a first cavity arm and a second cavity arm oriented relative to the gain medium and to each other so that a gain reduction effect persists in said gain medium when optical beams enter the gain medium from both arms simultaneously; optical feedback means in each cavity arm; and output coupling means in at least one of said cavity arms; the gain medium and the two cavity arms being further oriented to form a laser cavity having a length substantially equal to an odd multiple (h) of said pulse width, the relative lengths of said cavity arms being such that the gain medium is at a point in the laser cavity spaced from the center thereof by a multiple from zero to (h-1)/2 of said pulse width.
Claim 3
Dependent Claim
38 words
A generator as claimed in claim 1 wherein a output coupler is at a distal end of one of said cavity arms, and wherein a high reflection mirror is at a distal end of the other cavity arm.
Claim 4
Dependent Claim
17 words
A generator as claimed in claim 1 including means for collimating the output from the gain medium.
Claim 5
Dependent Claim
22 words
A generator as claimed in claim 1 including means for mode matching the output from the gain medium to the cavity arms.
Claim 6
Dependent Claim
18 words
A generator as claimed in claim 1 including means for optically filtering the output from the gain medium.
Claim 7
Dependent Claim
29 words
A generator as claimed in claim 1 wherein said cavity arms extend from the medium at angles of +θ and -θ, respectively to a collinear axis of the medium.
Claim 8
Dependent Claim
19 words
A generator as claimed in claim 6 wherein the angle θ is in the range from 6° to 25°.
Claim 9
Dependent Claim
36 words
A generator as claimed in claim 1 wherein the gain reduction effect is spatial hole burning, and wherein the width of the gain medium is sufficient to permit the hole burning effect to affect the gain.
Claim 10
Dependent Claim
45 words
A generator as claimed in claim 8 wherein the gain medium has a facet adjacent the cavity arms with a minimum width of (2l/n) sing, where 1 is the length of the gain medium and n is the index of refraction of the gain medium.
Claim 11
Dependent Claim
28 words
A generator as claimed in claim 1 wherein said gain medium is a diode laser array having an anti-reflection coating on the face thereof adjacent the cavity arms.
Claim 12
Dependent Claim
24 words
A generator as claimed in claim 10 wherein the face of said gain medium opposite the anti-reflection coated face has a high reflection coating.
Claim 13
Dependent Claim
29 words
A generator as claimed in claim 1 wherein said cavity arms are of substantially equal length, resulting in said gain medium being at the center of the laser cavity.
Claim 14
Dependent Claim
27 words
A generator as claimed in claim 1 including means for controlling the odd harmonic, and thus the pulse width, for a laser cavity of a given length.
Claim 15
Dependent Claim
54 words
A generator as claimed in claim 13 wherein said optical feedback means for a cavity arm may be one of a high reflection mirror or output coupler at the distal end of the arm, and wherein said means for controlling includes means for adjusting the angle of at least one of said feedback means.
Claim 16
Dependent Claim
29 words
A generator as claimed in claim 13 wherein said means for controlling includes an external cavity of a length equal to said pulse width extending from said output coupler.
Claim 17
Dependent Claim
38 words
A generator as claimed in claim 13 wherein said means for controlling includes a weak partial reflector in at least one of said cavity arms and spaced from the gain medium by a multiple of said pulse width.
Claim 18
Dependent Claim
24 words
A generator as claimed in claim 13 wherein said means for controlling includes a tuning element in at least one of said cavity arms.
Claim 19
Dependent Claim
15 words
A generator as claimed in claim 1 wherein said pulses are optical square wave pulses.
Claim 20
Dependent Claim
18 words
A generator as claimed in claim 18 wherein said pulses have rise times of less than 200 ps.
Claim 21
Dependent Claim
18 words
A generator as claimed in claim 1 wherein said arms are formed by a length of free space.
Claim 22
Dependent Claim
21 words
A generator as claimed in claim 1 wherein at least one of said cavity arms is formed by an optical waveguide.
Claim 23
Dependent Claim
16 words
A generator as claimed in claim 21 wherein said optical waveguide is a coiled optical fiber.
Claim 24
Dependent Claim
13 words
A generator as claimed in claim 21 wherein said optical waveguide is looped.
Claim 25
Dependent Claim
24 words
A generator as claimed in claim 21 including an optical feedback means at the distal end of at least one of said optical waveguides.
Claim 26
Dependent Claim
41 words
A generator as claimed in claim 1 wherein said gain medium has anti-reflection coatings on both its front and rear facets, one of said cavity arms extending from the front facet and the other cavity arm extending from the rear facet.
Claim 27
Dependent Claim
49 words
A generator as claimed in claim 25 wherein each of said cavity arms is in the form of a loop having first and second legs, the legs of a given arm extending from the medium at angles of +θ and -θ, respectively, to a collinear axis of the medium.
Claim 28
Dependent Claim
47 words
A generator as claimed in claim 26 wherein said feedback means includes mirrors at the distal ends of each cavity arm leg, said mirrors being angled to reflect a light beam exiting from one leg of a cavity arm into the other leg of the cavity arm.
Claim 29
Dependent Claim
18 words
A generator as claimed in claim 26 wherein each of said loops is formed by an optical waveguide.
Claim 30
Dependent Claim
48 words
A generator as claimed in claim 1 wherein the laser cavity has a length which is many times greater than the length of the gain medium, so that pulses are in the gain medium for only a very small fraction of their travel time to the laser cavity.
References Cited (Backward Citations)
US4709368A
Cited
US4922498A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-03-03 | 1995-09-02 | 1996-03-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-03-03 | 1999-09-02 | 2000-03-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-03-03 | 2003-09-02 | 2004-03-03 | $7700.00 | Window Closed / Lapsed |