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The structural and optical characteristics of Ge/Si self-assembled quantum dots epitaxially grown on Si(001) were studied. The Ge islands were grown in an industrial 200 mm single-wafer chemical vapor deposition reactor. The islands showed a maximum photoluminescence at 1.55 microns wavelength. The photoluminescence energy was correlated to the three-dimensional quantum confinement energy and to the size and geometry of the clusters.

A study was conducted on GaAs/AlGaAs coupled quantum well mid-infrared intersubband stimulated emission under optical pumping. Two-color picosecond free-electron laser-based time-resolved pump-probe experiments were employed for gain measurements. The stimulated gain exhibited broadening caused by mid-infrared waveguide coupled high intensities. The stimulated gain may be applied in the development of long-wavelength intersubband lasers under optical pumping.

We have performed an electroabsorption spectroscopy of Ge/Si self-assembled islands simultaneously in the near-infrared and in the midinfrared spectral range. The investigated structure consists of self-assembled Ge/Si islands embedded in a p-i-n junction. This active region is inserted into a 3-μm-thick Si0.98Ge0.02 waveguiding layer. Under a positive applied bias, the injected carriers give rise to a current-induced absorption resonant at 185 meV along with an enhanced transmission around 800 meV. The 185-meV resonance is polarized along the growth axis of the islands. The assignment of the optical transitions is made on the basis of a 14-band quantum well k·p calculation. We show that the midinfrared electroabsorption of the islands is associated with a bound-to-continuum transition between the ground states and the wetting layer states. The enhancement of the transmission is correlated to the bleaching of the interband absorption which results from hole injection in the islands. The carrier density and the parameters governing the carrier dynamics in the islands are deduced from the midinfrared modulation amplitude. An Auger recombination coefficient in the islands, C=1.6×10-30 cm6 s-1, is deduced at room temperature. [ABSTRACT FROM AUTHOR]

We report dramatic enhancement of 1.3-1.5 µm room-temperature emission from self-assembled Ge/Si islands in highly confining microcavities on silicon on insulator. The microcavities are fabricated either by creating defects in two-dimensional silicon-based photonic crystals or by etching the silicon layer in order to form isolated micropillars. The optical emission is characterized by nonlinear evolution with pump power, the nonlinearity being more pronounced as the microcavity size is reduced. Both the nonlinearity and luminescence extraction are enhanced in photonic crystals with large air filling factors. The results are interpreted in terms of carrier localization. The luminescence extracted is more than two orders of magnitude higher than that of the unprocessed sample while it is 1% that of a single InGaAs quantum well. This system appears to be a promising alternative for microsources on silicon at telecommunication wavelengths that are fully compatible with silicon-based processing technologies. [ABSTRACT FROM AUTHOR]

The article explains the direct and indirect band gap room temperature electroluminescence exhibited by the Ge diodes. The results show that the amplitude of the direct band gap recombination is equivalent to one of the indirect band gaps.

The bound-to-continuum absorption of InGaAs quantum dots are examined as a function of n-doping. The oscillations have resulted from the standing wave pattern caused by the interference of optical beams incident and totally reflected at the sample/air interface.

The metal organic vapor phase epitaxy of InAsP/InP(001) quantum dots with a voluntary V-alloying obtained due to an additional phosphine flux during InAs quantum dot growth is reported. The results from the study offer insight into the effects of the phosphine flow and of the alloying on the quantum dot growth, structural, and optical properties.

A combination of Ge/Si self-assembled islands with microcavities on silicon on insulator leads to enhanced emission at room temperature in 1.3-1.55 mu m spectral range. This system appears to be a promising alternative for microsources on silicon telecommunication wavelengths.

A study was conducted to investigate the silicon-based near-infrared photodetector using a waveguide with strong optical confinement. The result shows high-difference index waveguide with a silicon-on-insulator substrate.

Photoluminescence (PL) is the most widely used optical characterization of self-assembled quantum dots, as it provides valuable distribution and energy spectrum information. Intraband transitions have been considered by some authors to further analyze the energy spectrum of quantum dots. The photoinduced intraband absorption dependence in quantum dots has been investigated, and intraband absorption is enhanced when dots were directly populated via a wetting layer.

A high-speed saturable-absorber-based device (response time below 2.5 ps) providing a significant amplitude stabilization is demonstrated. The experimental results allow estimating that the amplitude fluctuations of the output should be reduced by about 90% compared to the input fluctuations, within the input power range of (5–18 μJ/cm2). This device has been studied in view of its possible use for bit-1 noise reduction. When combined with a state-of-art saturable absorber device, this could provide a simple and compact scheme for the complete reamplification and reshaping regeneration of digital optical signals. [ABSTRACT FROM AUTHOR]