Transient behaviour of quantum-dot saturable absorber mirrors at varying excitation fluence
2014 (English)In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 116, no 4, 919-927 p.Article in journal (Refereed) Published
We present results from studying the carrier dynamics in self-assembled InAs/GaAs quantum-dot saturable absorbers intended for mode-locking of solid-state lasers. Four samples are examined, featuring controlled variations in the resonance condition of the electric field inside the absorber, the number of quantum-dot (QD) layers and the thickness of the GaAs barriers between these QD layers. Pump-probe experiments are conducted at a wide range of excitation fluences and reveal a fast relaxation component of the initial bleaching at low excitation fluences, while a slowly relaxing induced transparency becomes dominant at higher excitation fluences. Time-resolved photoluminescence measurements reveal a large and slowly relaxing induced transparency due to a capture of excess carriers from the barrier bands into the QDs and a slow radiative recombination there. The resonance condition as well as the thickness of the barriers between the QD layers can be used to control the relaxation behaviour. The fastest response is obtained in a structure with an increased number of QD layers at each individual anti-node of the electric field, which is attributed to the appearance of efficient non-radiative recombination channels and capture centres. These centres are probably related to dislocations and other defects appearing in thick QD stacks.
Place, publisher, year, edition, pages
2014. Vol. 116, no 4, 919-927 p.
Atom and Molecular Physics and Optics
IdentifiersURN: urn:nbn:se:kth:diva-131454DOI: 10.1007/s00340-014-5778-1ISI: 000341369600017ScopusID: 2-s2.0-84906951488OAI: oai:DiVA.org:kth-131454DiVA: diva2:656437
Updated from submitted to published.
QC 201410092013-10-152013-10-152014-10-09Bibliographically approved