Coherent light generators – Particular resonant cavity – Distributed feedback
Patent
1995-06-05
1996-10-22
Bovernick, Rodney B.
Coherent light generators
Particular resonant cavity
Distributed feedback
H01S 318, H01S 3805, H01S 3103, H01S 3101
Patent
active
055685048
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a surface-emitting laser diode in which different emission directions can be realized.
2. Description of the Related Art
European Patent Document EP-A-0 442 002 describes a radiation-generating semiconductor component in which there are present on the surface of the semiconductor material spatial periodic structures which are coated with a thin metallic film. Surface plasmon polaritons are excited on the surface of this metallic film by photons generated in the active layer. An extremely focused emission from the surface is achieved by this excitation of surface modes. Surface plasmon polaritons are transverse electric (TE) or transverse magnetic (TM) surface modes which can propagate at the interface between two different media. The excitation of these modes requires a suitable periodic structure of the interface, which is formed in the case of the component described by a spatial structure, produced by etching, for example, of the semiconductor surface. The loss mechanisms which occur in conventional radiation-generating components and limit efficiency can be avoided, a greatly reduced line width of the emitted light and a drastic increase in the external quantum efficiency being achieved simultaneously. The emission takes place, in addition, with a defined polarization direction which is fixed by the arrangement and alignment of the periodic surface structure.
European Patent Document EP-A-0 360 011 describes a tunable DFB laser diode in which the active layer and the tuning layer are arranged transversely relatively to one another and can be driven separately via an intermediate layer which is located therebetween. This laser diode, known to experts as a TTG-DFB laser diode, has come to exist in the meantime in various modifications which relate, in particular, to various arrangements of the contacts required for the supply leads. Such diodes can be constructed on conductive and on semi-insulating substrates. The layer structure can be adapted in detail to the respective requirements, in particular in the case of the production of highly integrated components.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a surface-emitting laser diode which emits in an extremely focused fashion and whose emission direction can be varied without varying the structural design or the arrangement of the diode.
This and other objects and advantages of the invention are achieved by means of the tunable laser diode having two layers which are separated by a central layer, are arranged parallel, and with reference to the planes of the layers, transverse to one another and are made from semiconductor materials having different energy band gaps, and of which one is provided as active layer and one as tuning layer and which are connected in an electrically conductive fashion to contacts in such a way that a separate current injection into the active layer and into the tuning layer can be performed, having a spatial periodic structure which is present in a region, arranged with reference to the planes of the layers in a fashion transverse to a region provided for generating radiation in the active layer, of the surface of an outermost semiconductor layer and is covered at least partially with a metallic film, the height of this structure and the length of in each case one period of the spatial periodic structure, the minimum distance of the metallic film from the active layer, and the thickness of the metallic film being dimensioned such that during operation of the laser diode surface modes are excited by photons generated in the active layer on the surface of the metallic film averted from the active layer, and having measures for achieving a laser resonance. Further embodiments of the invention provide that the measures for achieving a laser resonance comprise a DFB (distributed feedback) grating which is arranged parallel and with reference to the planes of the layers transverse to the active layer. Alternate
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patent: 5008893 (1991-04-01), Amann et al.
E. Gornik et al., "Surface Plasmon Enhanced Light Emission in GaAs/AlGaAs Light Emitting Diodes", Proceedings SPIE, vol. 1362 Physical Concepts of Materials for Novel Optoelectronic Device Applications II: Device Physics and Applications (1990), pp. 1-13. (No month available).
Kan et al., "Beam-Scannable Light Source With the Grating Output Coupler", 2419 Japanese Journal of Applied Physics Supplements, 16th Int. Conf. Solid State Devices and Materials, (1984), Aug. 30-Sep. 1, Tokyo, Japan, pp. 141-144.
Japanese Abstract, "Semiconductor Light Generator", JP 60-123084, vol. 9, No. 280 E-356) (2003) Nov. 8, 1985.
Microelectronic Engineering, vol. 19, No. 1-4, Sep. 1992, pp. 57-59.
Gornik Erich
Kock Anton
Bovernick Rodney B.
McNutt Robert
Siemens Aktiengesellschaft
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