Polarization dependences of electroluminescence and absorption of vertically correlated InAs/GaAs QDs

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

“…Laser structures were grown by molecular beam epitaxy on n + -GaAs (001) substrate and are similar to the structure described in [6,8]. The structure consisted of an n -doped bottom Al 0.35  Ga 0.75 As layer with a thickness of 1.5 μm, a waveguide undoped GaAs layer with a thickness of 480 nm containing ten layers of In(Ga)As QD, a p -doped upper Al 0.35  Ga 0.75 As layer with a thickness of 1.5 μm, and a p + -doped contact GaAs layer.…”

“…The refractive index of the upper and lower Al 0.35  Ga 0.75 As layers differed from that of the central layer, which confined light within the central part of the undoped SLQD-containing region. The vertical alignment of QDs was observed by transmission electron microscopy (see Figure 1) [6,8] .…”

“…The cavity length was 3.5 mm, the absorber length was 10% of the cavity length, and the sections were electrically isolated by the gap in the contact. This laser design is in fact standard and is described in various publications [2,8-10] but differs from them in that the active layer is SLQD, formed by ten QD layers and thin barrier layers between them. The devices were mounted on a copper heat sink; all measurements were performed at room temperature.…”

“…Absorption measurements were provided as described in [8,9] using this device. The experimental setup is shown on Figure 2b,c.…”

“…As shown in [7,8], the structure with ten tunnel-coupled layers of In(Ga)As/GaAs QDs exhibits the Wannier-Stark effect and is a quantum dot superlattice (QDSL). We have observed the EL and absorption spectra for light polarized in the plane perpendicular to the growth axis ( x and y ) in the same spectral range as that for light polarized along the growth direction ( z ) of the structure.…”