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Proceedings Paper

Self-aligned BCB planarization method for high-frequency signal injection in a VCSEL with an integrated modulator
Author(s): Ludovic Marigo-Lombart; Jean-Baptiste Doucet; Aurélie Lecestre; Benjamin Reig; Bernard Rousset; Hugo Thienpont; Krassimir Panajotov; Guilhem Almuneau
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Paper Abstract

The huge increase of datacom capacities requires lasers sources with more and more bandwidth performances. Vertical-Cavity Surface-Emitting Lasers (VCSEL) in direct modulation is a good candidate, already widely used for short communication links such as in datacenters. Recently several different approaches have been proposed to further extend the direct modulation bandwidth of these devices, by improving the VCSEL structure, or by combining the VCSEL with another high speed element such as lateral slow light modulator or transistor/laser based structure (TVCSEL).

We propose to increase the modulation bandwidth by vertically integrating a continuous-wave VCSEL with a high-speed electro-modulator. This vertical structure implies multiple electrodes with sufficiently good electrical separation between the different input electrical signals. This high frequency modulation requires both good electrical insulation between metal electrodes and an optimized design of the coplanar lines. BenzoCyclobutene (BCB) thanks to its low dielectric constant, low losses, low moisture absorption and good thermal stability, is often used as insulating layer. Also, BCB planarization offers the advantages of simpler and more reliable technological process flow in such integrated VCSEL/modulator structures with important reliefs. As described by Burdeaux et al. a degree of planarization (DOP) of about 95% can be achieved by simple spin coating whatever the device thickness. In most of the cases, the BCB planarization process requires an additional photolithography step in order to open an access to the mesa surface, thus involving a tight mask alignment and resulting in a degraded planarization.

In this paper, we propose a self-aligned process with improved BCB planarization by combining a hot isostatic pressing derived from nanoimprint techniques with a dry plasma etching step.

Paper Details

Date Published: 28 April 2016
PDF: 9 pages
Proc. SPIE 9892, Semiconductor Lasers and Laser Dynamics VII, 98921R (28 April 2016); doi: 10.1117/12.2227529
Show Author Affiliations
Ludovic Marigo-Lombart, LAAS, CNRS, Univ. de Toulouse (France)
Vrije Univ. Brussel (Belgium)
Jean-Baptiste Doucet, LAAS, CNRS, Univ. de Toulouse (France)
Aurélie Lecestre, LAAS, CNRS, Univ. de Toulouse (France)
Benjamin Reig, LAAS, CNRS, Univ. de Toulouse (France)
Bernard Rousset, LAAS, CNRS, Univ. de Toulouse (France)
Hugo Thienpont, Vrije Univ. Brussel (Belgium)
Krassimir Panajotov, Vrije Univ. Brussel (Belgium)
Guilhem Almuneau, LAAS, CNRS, Univ. de Toulouse (France)

Published in SPIE Proceedings Vol. 9892:
Semiconductor Lasers and Laser Dynamics VII
Krassimir Panajotov; Marc Sciamanna; Angel Valle; Rainer Michalzik, Editor(s)

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