Room temperature passive mode-locked laser based on InAs/GaAs quantum-dot superlattice

Nanoscale Research Letters (Impact Factor: 2.78). 10/2012; 7(1):545. DOI: 10.1186/1556-276X-7-545
Source: PubMed


Passive mode-locking is achieved in two sectional lasers with an active layer based on superlattice formed by ten layers of quantum dots. Tunnel coupling of ten layers changes the structural polarization properties: the ratio between the transverse electric and transverse magnetic polarization absorption coefficients is less by a factor of 1.8 in the entire electroluminescence spectrum range for the superlattice.

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Available from: Mikhail Buyalo, Jan 13, 2014
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    ABSTRACT: The polarization anisotropy of electroluminescence and absorption in a ten-layer system of vertically correlated InAs quantum dots separated by 8.6-nm-thick GaAs spacer layers is investigated experimentally. The quantum-dot system is built into a two-section laser structure with sections of equal length. It is found that the polarization anisotropy in this system is smaller than the anisotropy in similar systems with a single layer of quantum dots or quantum-dot molecules, but larger than that in a quantum-dot superlattice. The spectra of differential absorption in the structure under study for different strengths of the applied electric field are also investigated. The rate of variation in the Stark shift as a function of the electric field is determined, the results giving evidence of controlled quantum coupling between adjacent quantum dots in tenlayer vertically correlated InAs/GaAs quantum-dot systems with 8.6- and 30-nm-thick GaAs spacer layers. The measured polarization dependences are explained by the participation of heavy-hole ground states in optical transitions. This effect is defined by the two dimensional nature of the system under study.
    No preview · Article · Aug 2014 · Semiconductors
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    ABSTRACT: The spectral characteristics of a laser with an active region based on a ten-layer system of In(Ga)As/GaAs vertically correlated quantum dots with 4.5-nm GaAs spacer layers between InAs quantum dots are studied under the conditions of spontaneous and stimulated emission, depending on the current and the duration of pump pulses. Data obtained by transmission electron microscopy and electroluminescence and absorption polarization anisotropy measurements make it possible to demonstrate that the investigated system of tunnel-coupled InAs quantum dots separated by thin GaAs barriers represents a quantum-dot superlattice. With an increase in the laser pump current, the electroluminescence intensity increases linearly and the spectral position of the electroluminescence maximum shifts to higher energies, which is caused by the dependence of the miniband density-of-states distribution on the pump current. Upon exceeding the threshold current, multimode lasing via the miniband ground state is observed. One of the lasing modes can be attributed to the zero-phonon line, and the other is determined by the longitudinal-optical phonon replica of quantum-dot emission. The results obtained give evidence that, under conditions of the laser pumping of an In(Ga)As/GaAs quantum-dot superlattice, strong coupling between the discrete electron states in the miniband and optical phonons takes place. This leads to the formation of quantum-dot polarons, resulting from the resonant mixing of electronic states whose energy separation is comparable to the optical-phonon energy.
    No preview · Article · Oct 2015 · Semiconductors