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ABSTRACT: Electroluminescence and absorption spectra of a ten-layer InAs/GaAs quantum dot (QD) superlattice built in a two-section laser
with sections of equal length is experimentally studied at room temperature. The thickness of the GaAs spacer layer between
InAs QD layers, determined by transmission electron microscopy, is ∼6 nm. In contrast to tunnel-coupled QDs, QD superlattices
amplify the optical polarization intensity and waveguide absorption of the TM mode in comparison with the TE mode. It is found
that variations in the multimodal periodic spectrum of differential absorption of the QD superlattice structure are strongly
linearly dependent on the applied electric field. Differential absorption spectra exhibit the Wannier-Stark effect in the
InAs/GaAs QD superlattice, in which, in the presence of an external electric field, coupling of wave functions of miniband
electron states is suppressed and a series of discrete levels called the Wannier-Stark ladder states are formed.
Semiconductors 05/2012; 45(8):1064-1069. · 0.63 Impact Factor
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ABSTRACT: The absorption of uncoupled and tunnel-coupled vertically correlated quantum dots (QDs), measured at room temperature, has
been experimentally compared. It is revealed that matching of the laser wavelength and Stark shift for laser structures with
tunnel-coupled QDs leads to resonant absorption with formation of bound and antibound exciton states with a splitting energy
of ∼62 meV between them in QD molecules. For these states, an external field causes a large linear Stark shift (up to 68 meV).
For uncoupled QDs, one resonant absorption peak with the formation of an exciton (for which the Stark shift does not exceed
13 meV) is observed.
Semiconductors 04/2012; 43(4):490-494. · 0.63 Impact Factor
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I. M. Gadzhiev,
M. S. Buyalo, I. O. Bakshaev,
R. I. Grigor’ev,
S. O. Slipchenko,
N. A. Pikhtin,
A. Yu. Leshko,
A. V. Lyutetskiĭ,
D. A. Vinokurov,
I. S. Tarasov,
E. L. Portnoi
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ABSTRACT: Passive mode locking (PML) regimes in two-section lasers with quantum wells in broad waveguides operating at λ = 1.06 μm have
been studied. The room temperature spectrum of the saturable absorber section retains exciton peak at the absorption edge,
which decreases in amplitude shifts toward longer wavelengths by 18 meV when the reverse bias voltage is varied from 0 to
14 V. The PML regime is observed at relatively large voltages (above 9 V) that are necessary to compensate for the effect
of band broadening in the gain section by the Stark shift of absorption in the reversely biased section. The PML regime exists,
beginning with threshold values of the pumping current, and is characterized by a narrow RF signal with a 20-kHz linewidth.
As the reverse bias voltage on the absorber section is increased, a low-frequency amplitude modulation superimposes on the
mode-locked laser radiation.
Technical Physics Letters 04/2012; 36(11):1038-1041. · 0.56 Impact Factor
