Coherent light generators – Particular resonant cavity – Distributed feedback
Patent
1997-11-25
1999-09-14
Bovernick, Rodney
Coherent light generators
Particular resonant cavity
Distributed feedback
372102, 372 45, 372 46, 437129, H01S 308
Patent
active
059533617
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a DFB laser diode structure having complex optical grating coupling.
A DFB laser diode structure of this type is known from IEEE Photonics Technology Letters, Vol. 4, July 1992, pages 692-695 or from EP-A-0 507 956.
German reference DE 41 24 872 A1 or B. Borchert et al., Electronics Letters, Vol. 29 (1993), pages 210-211 discloses a DFB laser diode structure that comprises all features of a laser diode structure of the species initially cited, except for the features that the layer of the index material and the layer of the absorption semiconductor material are respectively composed of volumetric material and both the layer of the volumetric index material as well as the layer of the volumetric absorption semiconductor material are located between the one cladding layer and the relief surface in the projections of the grating.
Given this known structure, the layer of the index semiconductor material is present in the defined forward projections of the optical grating, but the layer of the absorption semiconductor material is located only in the defined backward projections of this grating.
These forward projections and backward projections are constructed with, for example, a triangular profile. In this case, the layer made from the absorption semiconductor material which is required for the complex grating coupling should be constructed only at the vertices of the triangular backward projections of the holographically produced grating. Consequently, the effect of the complex coupling depends decisively on how reproducibly the grating shape of the grating, which forms a Bragg grating, can be produced. Fluctuations in the grating shape, which can occur owing to unavoidable fluctuations in the technical process parameters during the production of the grating, therefore have a particularly strong effect in the case of this form of realization of the complex coupling on the intensity of the complex coupling and thus on the spectral characteristics of the DFB laser diode structure.
SUMMARY OF THE INVENTION
In general the present invention is a DFB laser diode structure having complex optical grating coupling. A laser-active layer is arranged between two optical cladding layers made from semiconductor material of mutually opposite conductivity types. A layer of an index semiconductor material in the form of volumetric material is arranged at a side of one of the two cladding layers facing away from the laser-active layer. A layer of an absorption semiconductor material in the form of volumetric material is arranged at a side of the layer of index semiconductor material facing away from the one cladding layer. An optical grating constructed in the layer is made from the index semiconductor material and the layer made from the absorption semiconductor material, in the form of a relief surface which is averted from the laser-active layer and defines forward projections of the grating pointing in the direction away from the laser-active layer and backward projections of the grating pointing towards the laser-active layer. The layer made from the index semiconductor material and the layer made from the absorption semiconductor material are of mutually opposite conductivity types. Both the layer made from the index semiconductor material and the layer made from the absorption semiconductor material are located between the one cladding layer and the relief surface in the forward projections of the grating. Located on the side, averted from the laser-active layer, of the relief surface is a body which abuts the relief surface and is made from a semiconductor material of the conductivity type of the one cladding layer. A further layer of semiconductor material in the form of volumetric material different from the index semiconductor material and absorption semiconductor material is located in the forward projections of the grating between the layers of the absorption and index semiconductor material and the relief surface. The body adjoining the relief surface is c
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IEEE Photonics Technology Letter, vol. 4, No. 7, Jul. 1992, Y. Luo et al., "Gain-Coupled . . . Grating," pp. 692-695.
IEEE Journal of Quantum Electronics, vol. 30, No. 6, Jun. 1994, W. Tsang et al, "Long-Wavelength . . . Epitaxy," pp. 1370-1380.
Electronics Letter, vol. 30, No. 1, Jan. 6, 1994, J. Zoz, "Dynamic . . . Grating," pp. 39-40.
Electronics Letters, vol. 28., No. 18, Aug. 27, 1992, G. P. Li et al, "1.55.mu.m . . . Grating," pp. 1726-1727.
American Institute of Physics, May 25, 1992, W. T. Tsang et al, "Semiconductor . . . Feedback," pp. 2580-2582.
Borchert Bernd
Stegmuller Bernhard
Bovernick Rodney
Kim Sung T.
Siemens Aktiengesellschaft
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