IV-VI resonant cavity enhanced photodetectors for the midinfrared

A resonant-cavity enhanced detector operating in the mid-infrared at a wavelength around 3.6 micron is demonstrated. The device is based on a narrow-gap lead salt heterostructure grown by molecular beam epitaxy. Below 140 K, the photovoltage clearly shows a single narrow cavity resonance, with a relative line width of only 2 % at 80 K.Comment: 2 figure

Centrosymmetric PbTe/CdTe quantum dots coherently embedded by epitaxial precipitation

A concept for the fabrication of highly symmetric quantum dots that are coherently embedded in a single crystalline matrix is demonstrated. In this approach, the formation of the quantum dots is induced by a transformation of an epitaxial 2D quantum well into an array of isolated precipitates with dimensions of about 25 nm. The formation process is driven by the immiscibility of the constituent materials resulting from their different lattice structures. The investigated PbTe/CdTe heterosystem combines two different cubic lattices with almost identical lattice constants. Therefore, the precipitated quantum dots are almost strain free and near thermodynamic equilibrium they exhibit the shape of small-rhombo-cubo-octahedrons. The PbTe/CdTe quantum dots, grown on GaAs substrates, display intense room temperature luminescence at wavelength around 3.2 micrometer, which makes them auspicious for applications in mid-infrared photonic devices.Comment: 12 pages, 3 figure

Comparison of IV-VI Semiconductor Microcavity Lasers for the Mid-Infrared with Active Regions of Different Dimensionality

A comparison between IV-VI vertical-cavity surface-emitting mid-infrared lasers containing active regions of different dimensionality is presented. Optically pumped laser emission is observed at wavelengths between 3.5 and 4.4 µm. The microcavities consist of high-reflectivity EuTe/PbEuTe Bragg mirrors, with active regions consisting of either a self-organized PbSe/PbEuTe quantum-dot superlattice, PbTe/PbEuTe multi-quantum wells or bulk-like PbTe. For the 0D active medium, laser emission is obtained at temperatures up to 150 K. The results for the lasers with 2D active region are similar to those with the 3D bulk-like active region, for which lasing is observed up to 317 K. The threshold pump intensity is only 4 kW/cm 2 at 195 K, and 15 W/cm 2 at room temperature

Continuous Wave Mid-Infrared IV-VI Vertical Cavity Surface Emitting Lasers

Continuous wave emission of mid-infrared IV-VI vertical-cavity surface-emitting laser structures with PbSe as active medium is demonstrated for the 6 to 8 µm wavelength region. The lasers are based on ultra-high finesse microcavity structures formed by high reflectivity EuSe/PbEuSe Bragg mirrors. Optically pumped cw laser emission is observed up to temperatures of 120 K. We achieved internal threshold pump intensities of down to 25 W/cm 2 , which is two orders of magnitude smaller than reported so far. The line width of the laser emission is only 18 µeV (0.9 nm) with a strong narrowing as compared to the line width of the cavity resonance. Continuous wave output powers are up to 4.8 mW

Plasmon-gating photoluminescence in graphene/GeSi quantum dots hybrid structures

The ability to control light-matter interaction is central to several potential applications in lasing, sensing, and communication. Graphene plasmons provide a way of strongly enhancing the interaction and realizing ultrathin optoelectronic devices. Here, we find that photoluminescence (PL) intensities of the graphene/GeSi quantum dots hybrid structures are saturated and quenched under positive and negative voltages at the excitation of 325 nm, respectively. A mechanism called plasmon-gating effect is proposed to reveal the PL dependence of the hybrid structures on the external electric field. On the contrary, the PL intensities at the excitation of 405 and 795 nm of the hybrid structures are quenched due to the charge transfer by tuning the Fermi level of graphene or the blocking of the excitons recombination by excitons separation effect. The results also provide an evidence for the charge transfer mechanism. The plasmon gating effect on the PL provides a new way to control the optical properties of graphene/QD hybrid structures