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Proceedings Paper

Picosecond pulse generation in monolithic GaN-based multi-section laser diodes
Author(s): Katarzyna Holc; Thomas Weig; Wilfried Pletschen; Klaus Köhler; Joachim Wagner; Ulrich T. Schwarz
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Paper Abstract

We develop a monolithic picosecond laser pulse generator, based on the classical design of a group-III-nitride Fabry-Pérot laser diode with electrically separated ridge sections. We use two different multi-section design variants, with the absorber section placed either in the center or at the end of the ridge. Profiting from the very low lateral conductivity in the p-type GaN top contact layer, we implement the multi-section concept just by etching off small sections of the top metalization on the ridge. The physical mechanism underlying short pulse generation within such system, operating in the 400 - 435nm wavelength range, strongly depends both on the reverse bias applied to the absorber and the forward current in the gain section. Varying the applied reverse bias affects both the absorption and the carrier lifetime in the absorber section through changes in the QW internal field. In consequence we can distinguish between different modes of operation. For moderately long carrier lifetimes the absorber stabilizes relaxation oscillations in the GHz frequency range and self-pulsation occurs, of relatively long duration. With increasing reverse bias, and thus decreasing carrier lifetime, we observe a transition to self-Q-switching. Finally, at large enough negative bias, the carrier life time in the absorber is so short that the laser diode operates in a passive self-mode-locking regime with a repetition rate of 87 GHz and pulse duration of 2 ps for a cavity length of 540 μm.

Paper Details

Date Published: 4 March 2013
PDF: 8 pages
Proc. SPIE 8625, Gallium Nitride Materials and Devices VIII, 862515 (4 March 2013); doi: 10.1117/12.2001774
Show Author Affiliations
Katarzyna Holc, Fraunhofer Institute for Applied Solid State Physics (Germany)
Thomas Weig, Fraunhofer Institute for Applied Solid State Physics (Germany)
Wilfried Pletschen, Fraunhofer Institute for Applied Solid State Physics (Germany)
Klaus Köhler, Fraunhofer Institute for Applied Solid State Physics (Germany)
Joachim Wagner, Fraunhofer Institute for Applied Solid State Physics (Germany)
Ulrich T. Schwarz, Fraunhofer Institute for Applied Solid State Physics (Germany)
Freiburg Univ. (Germany)

Published in SPIE Proceedings Vol. 8625:
Gallium Nitride Materials and Devices VIII
Jen-Inn Chyi; Yasushi Nanishi; Hadis Morkoç; Joachim Piprek; Euijoon Yoon; Hiroshi Fujioka, Editor(s)

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