Browse Prior Art Database

Multi-Waveguide/ Laser Coupling

IP.com Disclosure Number: IPCOM000034635D
Original Publication Date: 1989-Mar-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 3 page(s) / 45K

Publishing Venue

IBM

Related People

Flint, EB: AUTHOR [+3]

Abstract

A technique is described whereby a coupling enables self-alignment optical waveguides to be coupled to semiconductor lasers for multi- channel laser and waveguide arrays. Described is the use of optical fibers and silicon substrates, which make up the coupling, and alignment procedures for minimizing alignment problems. In the packaging of fiber-optic transmitters, optical waveguides (usually consisting of optical fibers) are coupled to a semiconductor laser diode. However, due to the size of the waveguide and laser components, alignment tolerances can cause difficulty in achieving optimum coupling, such as 5-10 um for multi-mode guides and less than 1 um for single-mode guides. Generally, laser components and support substrates are difficult to fabricate to close tolerances.

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Multi-Waveguide/ Laser Coupling

A technique is described whereby a coupling enables self-alignment optical waveguides to be coupled to semiconductor lasers for multi- channel laser and waveguide arrays. Described is the use of optical fibers and silicon substrates, which make up the coupling, and alignment procedures for minimizing alignment problems. In the packaging of fiber-optic transmitters, optical waveguides (usually consisting of optical fibers) are coupled to a semiconductor laser diode. However, due to the size of the waveguide and laser components, alignment tolerances can cause difficulty in achieving optimum coupling, such as 5-10 um for multi-mode guides and less than 1 um for single-mode guides. Generally, laser components and support substrates are difficult to fabricate to close tolerances. This causes the self-aligned waveguide/laser couplings to be difficult and expensive to fabricate.

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Typically, the laser is coupled to the waveguide, or fiber, by turning on the laser diode, manipulating the guide in front of the laser and then fixing it in place when the coupled power attains a maximum. This type of construction is particularly difficult and expensive to fabricate when multiple channels involving arrays of monolithic semiconductor lasers and fibers are used. The concept described herein provides a "self-aligned" optical waveguide/semiconductor laser coupling to overcome misalignments arising from large tolerances in the laser chip and housing supporting the waveguides. The coupling is particularly applicable where high density, parallel arrays of lasers and waveguides are used, as are used in multi-channel applications. The concept is also useful in "perma nent" waveguide/laser coupling applications, since the optical waveguides are rigidly supported by the laser chip. This minimizes waveguide misalignment problems during attachment. The optical waveguide/laser array coupling is designed for the mounting of multiple arrays. Four lasers coupled to four optical fibers are described, but much larger arrays can be accommodated using the same approach. Alignment between lasers and optical waveguides is accomplished by referencing the top surface of the laser array to the top surface (or processed surface) of the alignment fixture. Usually, the thickness of the laser array chip will vary by several microns. This causes difficulty in locating the laser output spot relative to the laser carrier. It is also difficult to position the optical fibers at the same height as the laser output spots. The design of the concept is to eliminate any locating uncertainties by referencing all dimensions from the top, or processed, surfaces. Optical fibers 10, as shown in Fig. 1, are fixed to silicon alignment fixture 11, which is mounted on laser carrier 12. Anisotropic etchants for the appropriate crystal orientations of silicon exist which provide accurate control of the groove depth by accurately controlling the wi...