US4723248A
Expired / Lapsed
US
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Optical limiter
Assignee: Honeywell International Inc
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Filing: 1985-06-11
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Granted: 1988-02-02
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Expires: 2005-06-11
Abstract
Abstract An optical device that stabilizes the power in a cw laser beam comprises a material whose absorption coefficient increases wth increasing incident intensity. The same device acts as an energy limiter and pulse shortener for a pulsed laser. In either case, the device can be located either within the laser cavity or outside it. In another embodiment, the device is placed into the cavity of a passively mode-locked laser to permit mode-locking with laser materials that have high gain-saturation energy. Materials suitable for use in the device include Cr-doped crystalline solids and organic solutions, such as laser dyes, saturable absorber dyes, etc.
Inventors
- 👤 Donald J. Harter
- 👤 Michael L. Shand
- 👤 Yehuda B. Band
- 👤 Harold Samelson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 12:43
CPC Classifications
H; H01; H01S; H01S3/00; H01S3/10; H01S3/11; H01S3/1123; H01S3/113; G; G02; G02F; G02F1/00; G02F1/35; G02F1/3523; H01S3/106; H01S3/1061
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
109 words
An optical limiter comprising a material that has a ground state, a first excited state, and a second excited state of higher energy than the first excited state, and has, over a range of incident wavelengths, (a) a cross section for excitation from the first excited state that is greater than the cross section for excitation from the ground state to the first excited state; (b) substantially no decay from the first excited state to states that have decay times longer than the time for decay from the first excited state to the ground state; and (c) rapid decay from the second excited state to the first excited state.
Claim 2
Dependent Claim
109 words
An optical limiter comprising a material that has a ground state, a first excited state, and a second excited state of higher energy than the first excited state, and has, over a range of incident wavelengths, (a) a cross section for excitation from the first excited state that is greater than the cross section for excitation from the ground state to the first excited state; (b) substantially no decay from the first excited state to states that have decay times longer than the time for decay from the first excited state to the ground state; and (c) rapid decay from the second excited state to the first excited state.
Claim 3
Dependent Claim
15 words
The limiter of claim 1 in which the limiter material is a Cr-doped crystalline solid.
Claim 4
Dependent Claim
25 words
The limiter of claim 2 in which the limiter material is selected from a group that consists of alexandrite, ruby, and MgO: Cr 3+ .
Claim 5
Dependent Claim
12 words
The limiter of claim 3 in which the limiter material is alexandrite.
Claim 6
Dependent Claim
20 words
The limiter of claim 1 in which the limiter material is a suitably contained laser dye or saturable absorber dye.
Claim 7
Dependent Claim
127 words
The combination of a laser of reduced output beam fluctuation having an optical limiter positioned in the laser beam path: the optical limiter comprising a material that has a ground state, a first excited state, and a second excited state of higher energy than the first excited state, and has, over a range of incident wavelength; (a) a cross section from the first excited state that is greater than the cross section for excitation from the ground state to the first excited state; (b) substantially no decay from the first excited state to states that have decay times longer than the time for decay from the first excited state to the ground state; and (c) rapid decay from the second excited state to the first excited state.
Claim 8
Dependent Claim
127 words
The combination of a laser of reduced output beam fluctuation having an optical limiter positioned in the laser beam path: the optical limiter comprising a material that has a ground state, a first excited state, and a second excited state of higher energy than the first excited state, and has, over a range of incident wavelength; (a) a cross section from the first excited state that is greater than the cross section for excitation from the ground state to the first excited state; (b) substantially no decay from the first excited state to states that have decay times longer than the time for decay from the first excited state to the ground state; and (c) rapid decay from the second excited state to the first excited state.
Claim 9
Dependent Claim
15 words
The combination of claim 6 in which the optical limiter is within the laser cavity.
Claim 10
Dependent Claim
181 words
A passively mode-locked laser comprising: (a) a laser medium, (b) means for exciting the laser medium to emit coherent radiation; (c) reflective elements forming an optical resonator, which encloses the laser medium and is adapted for maintaining an oscillating beam of coherent radiation along a path in the resonator, (d) a saturable absorber in the beam path in the resonator, and (e) an optical limiter in the beam path of the resonator, said optical limiter comprising a material that has a ground state, a first excited state, and a second excited state of higher energy than the first excited state, and has, over a range of incident wavelengths; (i) a cross section for excitation from the first excited state that is greater than the cross section for excitation from the ground state to the first excited state; (ii) substantially no decay from the first excited state to states that have decay times longer than the time for decay from the first executed state to the ground state; and (iii) rapid decay from the second excited state to the first excited state.
Claim 11
Dependent Claim
181 words
A passively mode-locked laser comprising: (a) a laser medium, (b) means for exciting the laser medium to emit coherent radiation; (c) reflective elements forming an optical resonator, which encloses the laser medium and is adapted for maintaining an oscillating beam of coherent radiation along a path in the resonator, (d) a saturable absorber in the beam path in the resonator, and (e) an optical limiter in the beam path of the resonator, said optical limiter comprising a material that has a ground state, a first excited state, and a second excited state of higher energy than the first excited state, and has, over a range of incident wavelengths; (i) a cross section for excitation from the first excited state that is greater than the cross section for excitation from the ground state to the first excited state; (ii) substantially no decay from the first excited state to states that have decay times longer than the time for decay from the first executed state to the ground state; and (iii) rapid decay from the second excited state to the first excited state.
Claim 12
Dependent Claim
13 words
The mode-locked laser of claim 8 in which the laser medium is alexandrite.
Claim 13
Dependent Claim
17 words
The mode-locked laser of claim 9 in which the saturable absorber is a suitably contained cryptocyanine dye.
Claim 14
Dependent Claim
20 words
The mode-locked laser of claim 8 in which the means for exciting the laser medium comprises a cw radiation source.
Claim 15
Dependent Claim
126 words
A process for stabilizing the power in a laser beam that comprises placing in the path of the laser beam a material that has a ground state, a first excited state, and a second excited state of higher energy than the first excited state, and has, at the wavelength of the laser beam, (a) a cross section for excitation from the first excited state that is greater than the cross section for excitation from the ground state to the first excited state; (b) substantially no decay from the first excited state to states that have decay times longer than the time for decay from the first excited state to the ground state, and (c) rapid decay from the second excited state to the first excited state.
Claim 16
Dependent Claim
126 words
A process for stabilizing the power in a laser beam that comprises placing in the path of the laser beam a material that has a ground state, a first excited state, and a second excited state of higher energy than the first excited state, and has, at the wavelength of the laser beam, (a) a cross section for excitation from the first excited state that is greater than the cross section for excitation from the ground state to the first excited state; (b) substantially no decay from the first excited state to states that have decay times longer than the time for decay from the first excited state to the ground state, and (c) rapid decay from the second excited state to the first excited state.
Claim 17
Dependent Claim
14 words
The process of claim 12 in which the material is a Cr-doped crystalline solid.
Claim 18
Dependent Claim
19 words
The process of claim 12 in which the material is a suitably contained laser dye or saturable absorber dye.
Claim 19
Dependent Claim
15 words
The process of claim 12 in which the material is placed within the laser cavity.
Claim 20
Dependent Claim
76 words
The process of claim 12 in which the laser beam is provided by a cw laser and the average intensity of the beam incident on the material is of the order of I sat , where ##EQU3## where h is Planck's content, c the speed of light, g the wavelength of the laser beam, r the beam radius, s 1 the ground state absorption cross section, and t f the lifetime of the first excited state.
Claim 21
Dependent Claim
142 words
A process for limiting the energy in a laser pulse that comprises placing in the path of the pulse, at a point where the incident energy during the pulse interval is at least about a predetermined energy, a material that has a ground state, a first excited state, and a second excited state of higher energy than the first excited state, and has, at the wavelength of the pulse, (a) a cross section for excitation from the first excited state that is greater than the cross section for excitation from the ground state to the first excited state; (b) substantially no decay from the first excited state to states that have decay times longer than the time for decay from the first excited state to the ground state, and (c) rapid decay from the second excited state to the first excited state.
Claim 22
Dependent Claim
142 words
A process for limiting the energy in a laser pulse that comprises placing in the path of the pulse, at a point where the incident energy during the pulse interval is at least about a predetermined energy, a material that has a ground state, a first excited state, and a second excited state of higher energy than the first excited state, and has, at the wavelength of the pulse, (a) a cross section for excitation from the first excited state that is greater than the cross section for excitation from the ground state to the first excited state; (b) substantially no decay from the first excited state to states that have decay times longer than the time for decay from the first excited state to the ground state, and (c) rapid decay from the second excited state to the first excited state.
Claim 23
Dependent Claim
60 words
The process of claim 17 in which the material is chosen so that the predetermined energy E is approximately related to the parameters of the material by ##EQU4## h is Planck's constant, c the speed of light, λ the wavelength of the pulse, r the pulse beam radius, and σ 1 the ground state absorption cross section of the material.
Claim 24
Dependent Claim
14 words
The process of claim 17 in which the material is a Cr-doped crystalline solid.
Claim 25
Dependent Claim
19 words
The process of claim 17 in which the material is a suitably contained laser dye or saturable absorber dye.
References Cited (Backward Citations)
US4633475A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-02-01 | 1991-08-03 | 1992-02-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-02-01 | 1995-08-03 | 1996-02-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-02-01 | 1999-08-03 | 2000-02-02 | $7700.00 | Window Closed / Lapsed |