Optical waveguides – Planar optical waveguide – Thin film optical waveguide
Reexamination Certificate
1999-06-17
2001-07-17
Healy, Brian (Department: 2874)
Optical waveguides
Planar optical waveguide
Thin film optical waveguide
C385S129000, C385S130000, C385S014000, C385S141000
Reexamination Certificate
active
06263140
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to an opto-electronic module for integration of active electro-optical components and passive waveguides for optical coupling to external waveguides.
The optical coupling between opto-electronic components critically determines the properties of opto-electronic systems or, respectively, the collaboration of these components with transmission media such as, for example, optical fibers connected thereto. The optical coupling should be optimally effective given simple and cost-beneficial technical realization. A monolithic integration with waveguides on substrates having larger dimensions is required given opto-electronic components having extremely small dimensions (below 100 &mgr;m) since a mechanical handling (transport or, respectively, mounting) of such individual micro-structure elements is possible only with difficulty or is even impossible. Arrangements wherein the active and the passive components are manufactured in the same material system have been proposed for such an optical coupling of active components and passive waveguides in, for example, the publication by T. Ido et al, “High-Speed MQW Electroabsorption Optical Modulators Integrated with Low-Loss Waveguides”, in IEEE Photonics Technology Letters, Vol. 7, pp. 170 through 172 (1995) and in the publication by R. Ben-Michael et al, “A Bi-Directional Transceiver PIC for Ping-Pong Local Loop Configurations Operating at 1.3-&mgr;m Wavelength”, in IEEE Photonics Technology Letters, Vol. 7, pp. 1424 through 1426 (1995). The installation of adiabatic tapers (sections of a waveguide tapering in one direction) also ensues upon employment of the same material components. The disadvantage is thereby that the manufacturing methods of such arrangements are extremely involved. In particular, they require multiple epitaxy steps and a considerable use of the semiconductor materials.
SUMMARY OF THE INVENTION
An object of the present invention is to specify an opto-electronic module in which active and passive components are integrated and that enables simple manufacture and handling.
This object is achieved with an optoelectronic module being provided on an upper surface of a substrate of semiconductor material. The upper surface has at least one electronic component with a longitudinal direction and a passive waveguide. The component is fashioned in a layer sequence grown epitaxially on the substrate with the layer sequence being formed by layers of a material selected from layers of semiconductor materials and mixed crystal compositions of one or more semiconductor materials. The passive waveguide is applied on the substrate as an integrated component part of the module and is arranged so that the waveguide couples radiation at a region of an optoelectronic component and at a terminal surface provided for external coupling with the waveguide conducting radiation between said region and said terminal surface. The passive waveguide is formed by a material that is formed on one or more constituents that are all different from every semiconductor material of the optoelectronic component. The component has an upper surface facing away from the substrate provided with a dielectric layer laterally with respect to the longitudinal direction of the component and at least one first contact on the dielectric layer and at least one second contact electrically connected to a lower layer of the component with the at least one second conductor having a lower part arranged laterally with respect to the lower direction of the component and a part applied on the dielectric layer.
Given the inventive module, the opto-electronic components that function as active components are fashioned as layer sequence epitaxially grown on a substrate. The epitaxial growth can ensue locally limited. Instead, a surface-wide layer sequence can be applied and can be subsequently re-etched locally limited. Passive waveguides are arranged in the free regions of the substrate surface, these passive waveguides connecting the active zones of the components to external terminal surfaces to which, for example, an optical fiber can be connected. What is critical for the inventive module is that the passive waveguides are composed of a material that does not belong to the material system that is employed for the active components.
The inventive module has the advantage that fundamentally all material systems can be employed that were previously employed for opto-electronic discrete components (for example, various compositions of InGaAsP, InGaAlAs, GaN, InGaAlP [sic], etc.). The layer structures required for the active components are grown on the substrates that are standard for the appertaining material system, whereby a substrate having relatively large dimensions can be selected. The layer sequences are grown laterally limited or etched back, so that the active components respectively occupy only a small portion of the substrate surface. The active components usually contain an optical waveguide that, for example, can be formed by the active layer of a laser diode or the like. Given an arrangement of the component in the interior of the substrate surface, this optical waveguide of the component does not extend up to the edge of the substrate and can therefore not be directly connected to external waveguides. Such a connection to external waveguides can also be made more difficult given a component arranged at the edge of the substrate surface in that the region of the waveguide provided in the component for the connection is too narrow for an efficient transition into an external waveguiding medium. Inventively, a passive waveguide is therefore proposed that produces the connection of the waveguide present in the active component with a terminal surface toward the outside. This passive waveguide can, in particular, be fashioned such that it connects relatively low and narrow to the active component and increasingly broadens in the plane of the substrate top and/or perpendicular thereto with increasing distance from the component and thus forms a type of taper that connects the narrow waveguide zone in the component to a terminal surface at the edge of the module that is clearly enlarged compared thereto. A plurality of waveguides can be connected to an active component. In particular, for example given a laser diode, a respective waveguide can be connected at both resonator end faces. In addition, waveguides can be connected to the active zone transversely relative to this longitudinal direction of the laser diode, for example in order to be able to control the beam propagation ensuing in the longitudinal direction of the laser diode.
Epitaxy processes such as, for example, MOVPE (metallo-organic vapor phase epitaxy), MBE (molecular beam epitaxy) or MOMBE (metallo-organic molecular beam epitaxy) can be utilized for manufacturing the opto-electronic components. The active components are laterally limited, for example, in that the layers are etched back. Standard etching techniques can be utilized for this. The components are covered with a mask, and the material in the region that is not covered is eroded by etching. Possible methods that can be utilized for this are, for example, IBE (ion beam etching), RIE (reactive ion beam etching), FIBE (focused ion beam etching), RIPE (resonant induced plasma etching), and CAIBE (chemical assisted ion beam etching). Instead of surface-wide growth and subsequent, local re-etching, it is possible to grow topically limited layer sequences by selective epitaxy. MOMBE or MOVPE can also be utilized for this.
The passive waveguides are manufactured in supplementary method steps. Inventively, materials are employed therefor that contain no constituents of the semiconductor materials employed for the active components. The passive waveguides therefore do not belong to the material system employed for the active components. This is also true when the active components in the module are manufactured of various material systems. The material of the passive waveguides fund
Healy Brian
Schiff & Hardin & Waite
Siemens Aktiengesellschaft
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