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Self-sustained pulsations in the output of an InAs quantum dot laser diode in the MHz range are reported. The characteristics (shape, range, and frequency) are presented for the free-running laser and when optical feedback in the Littrow configuration is applied. Bistability in the light-current characteristics is observed for operating wavelengths smaller than the gain peak, but it is not present for wavelengths above the gain peak and for the free-running laser, except at elevated temperatures. The temporal evolution of the envelopes of the optical spectra is very different for operation below, around, and above the gain peak, which might be related to a change of phase-amplitude coupling across the gain maximum, in agreement with the expectation for a two-level system. The time scale and the bifurcation scenario, supported by an initial blueshift of the emission wavelength of each longitudinal mode in time-resolved optical spectra, suggests that these are optothermal pulsations similar to those reported in quantum well amplifiers [Phys. Rev. E 68, 036209 (2003)]. The mechanism of pulsation seems to be a destabilization of bistable states (due to saturable absorption in the beam wings) by a slow thermal change in the waveguiding properties

The nonlinear optical response of self-assembled quantum dots to cw driving is analyzed via numerical simulations of a spatially resolved rate equation model. The saturation is shown to follow a behavior in between the one for a dominantly, homogeneously, and inhomogeneously broadened medium. Self-lensing is suggested to probe the refractive-index nonlinearities and to open a complementary way of characterizing phase-amplitude coupling (alpha factor) in quantum-dots samples. For conservative assumptions on current samples the minimum focal length is predicted to be +/-1.7 mm for an input beam with 15 mu m radius at a detuning of 1.1 inhomogeneous linewidths from gain center

We have observed saturation of absorption and gain in ensembles of InAs/GaAs self-assembled quantum dots at room temperature with continuous-wave driving in the 1.24-1.28 mu m wavelength range. The saturation intensity was found to be I-sat=(1.4-4.5) X 10(9) W/m(2) in absorption and I-sat =(0.2-3.8)X10(9) W/m(2) in gain, depending on the detuning. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3524824

Quantitative strain mapping of InAs/InP quantum dots with 1nm spatial resolution using dark field electron holography Appl. Phys. Lett. 99, 261911 (2011) Preparation of uncapped CdSe1−xSx semiconducting nanocrystals by mechanical alloying J. Appl. Phys. 110, 124306 (2011) Comparing retention and recombination of electrically injected carriers in Si quantum dots embedded in Si-rich SiNx films Appl. Phys. Lett. 99, 243501 (2011) Dilute-nitride GaInAsN/GaAs site-controlled pyramidal quantum dots Appl. Phys. Lett. 99, 181113 (2011) Dynamics of interatomic Coulombic decay in quantum dots J. Chem. Phys. 135, 144112 (2011) Additional information on J. Appl. Phys. Structural and optical properties of InAlAs=GaAlAs quantum dots grown by molecular beam epitaxy are studied using transmission electron microscopy and temperature-and time-resolved photoluminescence. The control of the recombination lifetime (50 ps-1.25 ns) and of the dot density (5.10 -8 -2.10 11 cm -3 ) strongly suggest that these material systems can find wide applications in opto-electronic devices as focusing non-linear dispersive materials as well as fast saturable absorbers.