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Proceedings Paper

Toward more efficient fabrication of high-density 2D VCSEL arrays for spatial redundancy and/or multi-level signal communication
Author(s): Hendrik Roscher; Philipp Gerlach; Faisal Nadeem Khan; Andrea Kroner; Martin Stach; Alexander Weigl; Rainer Michalzik
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Paper Abstract

We present flip-chip attached high-speed VCSELs in 2-D arrays with record-high intra-cell packing densities. The advances of VCSEL array technology toward improved thermal performance and more efficient fabrication are reviewed, and the introduction of self-aligned features to these devices is pointed out. The structure of close-spaced wedge-shaped VCSELs is discussed and their static and dynamic characteristics are presented including an examination of the modal structure by near-field measurements. The lasers flip-chip bonded to a silicon-based test platform exhibit 3-dB and 10-dB bandwidths of 7.7 GHz and 9.8 GHz, respectively. Open 12.5 Gbit/s two-level eye patterns are demonstrated. We discuss the uses of high packing densities for the increase of the total amount of data throughput an array can deliver in the course of its life. One such approach is to provide up to two backup VCSELs per fiber channel that can extend the lifetimes of parallel transmitters through redundancy of light sources. Another is to increase the information density by using multiple VCSELs per 50 μm core diameter multimode fiber to generate more complex signals. A novel scheme using three butt-coupled VCSELs per fiber for the generation of four-level signals in the optical domain is proposed. First experiments are demonstrated using two VCSELs butt-coupled to the same standard glass fiber, each modulated with two-level signals to produce four-level signals at the photoreceiver. A four-level direct modulation of one VCSEL within a triple of devices produced first 20.6 Gbit/s (10.3 Gsymbols/s) four-level eyes, leaving two VCSELs as backup sources.

Paper Details

Date Published: 21 April 2006
PDF: 12 pages
Proc. SPIE 6185, Micro-Optics, VCSELs, and Photonic Interconnects II: Fabrication, Packaging, and Integration, 61850V (21 April 2006); doi: 10.1117/12.662121
Show Author Affiliations
Hendrik Roscher, Ulm Univ. (Germany)
Philipp Gerlach, Ulm Univ. (Germany)
Faisal Nadeem Khan, Ulm Univ. (Germany)
Andrea Kroner, Ulm Univ. (Germany)
Martin Stach, Ulm Univ. (Germany)
Alexander Weigl, Ulm Univ. (Germany)
Rainer Michalzik, Ulm Univ. (Germany)

Published in SPIE Proceedings Vol. 6185:
Micro-Optics, VCSELs, and Photonic Interconnects II: Fabrication, Packaging, and Integration
Hugo Thienpont; Mohammad R. Taghizadeh; Peter Van Daele; Jürgen Mohr, Editor(s)

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