Patent EP0476603A2 successfully refreshed from Google Patents.
US4754459A
Expired / Lapsed
US
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Semiconductor lasers
Assignee: British Telecommunications PLC
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Filing: 1985-10-07
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Granted: 1988-06-28
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Expires: 2005-10-07
Abstract
Abstract The emission linewidth of a semiconductor laser can be reduced by operating it at a wavelength which is less than the wavelength of maximum gain at the threshold current, λ max. An assembly for carrying out such operation comprises a ridge waveguide laser provided with a distributed feedback (DFB) grating. The period of the grating is selected to give a predetermined emission wavelength to the laser which is shorter than λ max.
Inventors
- 👤 Leslie D. Westbrook
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 21:35
CPC Classifications
H; H01; H01S; H01S5/00; H01S5/0014; H01S5/10; H01S5/12; H01S5/20; H01S5/22; H01S5/125; H01S5/14
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
70 words
A laser assembly including a semiconductor laser structure, the improvement comprising means for selecting the emission wavelength of the laser structure, the selected wavelength being shorter than the wavelength of maximum gain at the threshold current, λmax, by an amount such that the linewidth enhancement factor α at λmax, αmax, and α at the wavelength of the emitted radiation, α e , are related in the manner α.sub.e ≦, 9αmax.
Claim 2
Dependent Claim
70 words
A laser assembly including a semiconductor laser structure, the improvement comprising means for selecting the emission wavelength of the laser structure, the selected wavelength being shorter than the wavelength of maximum gain at the threshold current, λmax, by an amount such that the linewidth enhancement factor α at λmax, αmax, and α at the wavelength of the emitted radiation, α e , are related in the manner α.sub.e ≦, 9αmax.
Claim 3
Dependent Claim
19 words
A laser assembly according to claim 1 wherein αmax and α e are related in the manner α.sub.e ≦0.8αmax.
Claim 4
Dependent Claim
20 words
A laser assembly according to claim 1 wherein α max and α e are related in the manner α.sub.e ≦0.7αmax.
Claim 5
Dependent Claim
27 words
A laser assembly according to any of the preceding claims wherein the means for selecting the emission wavelengths of the laser structure comprises a distributed feedback grating.
Claim 6
Dependent Claim
31 words
A laser assembly according to any one of claims 1-3 wherein the means for selecting the emission wavelength of the laser structure comprises a distributed feedback grating and an external cavity.
Claim 7
Dependent Claim
34 words
A laser assembly according to any one of claims 1-3, wherein the selected emission wavelength of the laser structure lies in one of the ranges 1.2 to 1.35 μm and 1.48 to 1.65 μm.
Claim 8
Dependent Claim
26 words
A laser assembly according to any one of claims 1-3, wherein the means for selecting the emission wavelength of the laser structure comprise an external cavity.
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) | 1991-06-28 | 1991-12-28 | 1992-06-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-06-28 | 1995-12-28 | 1996-06-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-06-28 | 1999-12-28 | 2000-06-28 | $7700.00 | Window Closed / Lapsed |