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Proceedings Paper

Optical bandwidth broadening in two-section passively mode-locked InAs quantum dot lasers in the random population regime
Author(s): P. Finch; M. Hutchings; P. Blood; P. M. Smowton; Angela D. Sobiesierski; I. O'Driscoll
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Paper Abstract

Optical emission spectra, optical puslewidths and optical gain spectra are compared as a function of temperature using different sections of gain length for a passively mode-locked InAs quantum dot device. By increasing the length of the gain section, we decrease the threshold condition for mode-locking which allows access to a greater gain bandwidth. At 300 K, when the dots states and wetting layer are in thermal equilibrium, a decrease in the threshold condition results in little change in the width of the optical emission spectra and the corresponding optical pulsewidths. At 80 K, where the dot states are randomly populated, the same decrease in the threshold condition, results in a near doubling of optical emission spectra and a reduction in the optical pulsewidth from 910 fs to 600 fs. These changes in pulsewidth were obtained with only a modest 20% reduction of threshold condition from 14 cm-1 to 11 cm-1 which corresponds to an increase of the gain section length from 2 mm to 2.6 mm. The experimental results are qualitatively explained using a simple set of rate equations, which take explicit account of the photon density in the cavity. A reduction in the cavity loss results in an increase in the width of the gain spectrum at and above threshold as dots of different sizes in the inhomogeneous distribution are no longer coupled via carrier escape to the wetting layer.

Paper Details

Date Published: 10 March 2015
PDF: 10 pages
Proc. SPIE 9382, Novel In-Plane Semiconductor Lasers XIV, 93820C (10 March 2015); doi: 10.1117/12.2079352
Show Author Affiliations
P. Finch, Tyndall National Institute (Ireland)
Cork Institute of Technology (Ireland)
M. Hutchings, Syracuse Univ. (United States)
P. Blood, Cardiff Univ. (United Kingdom)
P. M. Smowton, Cardiff Univ. (United Kingdom)
Angela D. Sobiesierski, Cardiff Univ. (United Kingdom)
I. O'Driscoll, Tyndall National Institute (Ireland)
Cork Institute of Technology (Ireland)


Published in SPIE Proceedings Vol. 9382:
Novel In-Plane Semiconductor Lasers XIV
Alexey A. Belyanin; Peter M. Smowton, Editor(s)

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