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Efficient room-temperature (RT) continuous-wave (CW) lasing operation of the 1.3 μm MBE (molecular-beam epitaxy) In(Ga)As/GaAs quantum-dot (QD) top-emitting oxide-confined vertical-cavity surface-emitting diode lasers (VCSELs) for the second-generation optical-fibre communication has been achieved. In their design, a concept of a QD inside a quantum well (QW) has been utilized. The proposed In(Ga)As/GaAs QD active region is composed of five groups of three 8 nm In 0.15 Ga 0.85 As QWs, each containing one InAs QD sheet layer. In each group located close to successive anti-node positions of the optical standing wave within the 3λ cavity, QWs are separated by 32 nm GaAs barriers. Besides, at both active-region edges, additional single InGaAs QWs are located containing single QD layers. For the 10 μm diameter QD VCSELs, the RT CW threshold current of only 6.2 mA (7.9 kA cm −2 ), differential efficiency of 0.11 W A −1 and the maximal output power of 0.85 mW have been recorded. The experimental characteristics are in excellent agreement with theoretical ones obtained using the optical-electrical-thermal-recombination self-consistent computer model. According to this, for the 10 μm devices, the fundamental linearly polarized LP 01 mode remains the dominating one up to the current of 9.1 mA. The lowest RT CW lasing threshold below 5 mA is expected for 6 μm devices.

Herein, a novel hydrogel-derived three-dimensional network-like nanostructured CoO X /Co–N–C­(800) catalyst was synthesized. CoO X nanoparticles are embedded on N-doped carbon with single Co atoms anchored after pyrolysis. The as-prepared CoO X /Co–N–C­(800) catalyst possesses excellent electrochemical performance toward the oxygen reduction reaction with a positive onset and half-wave potential of 0.95 and 0.88 V (vs RHE), respectively, including almost a four-electron pathway (3.97) and better durability compared with the 20% commercial Pt/C catalyst in an alkaline electrolyte. Also, the results demonstrate that the high performance is attributed to the synergistic effect of CoO X nanoparticles and single Co atoms.

We present the fabrication of 1.3 µm waveband p-doped InAs quantum dot (QD) vertical cavity surface emitting lasers (VCSELs) with an extremely simple process. The continuous-wave saturated output power of 1.1 mW with a lasing wavelength of 1280 nm is obtained at room temperature. The high-speed modulation characteristics of p-doped QD VCSELs of two different oxide aperture sizes are investigated and compared. The maximum 3 dB modulation bandwidth of 2.5 GHz can be achieved at a bias current of 7 mA for a p-doped QD VCSEL with an oxide aperture size of 10 µm in the small signal frequency response measurements. The crucial factors for the 3 dB bandwidth limitation are discussed according to the parameters' extraction from frequency response.

Due to all bands of hyperspectral data have the same imaging area, it is reasonable to believe that the dictionary can sparse represent one band may also represent the other bands sparsely. Based on this property, this paper presents a new compression frame for hyperspectral data using sparse representation, and a simplified algorithm under this frame is also proposed. The basic idea of the proposed algorithm is to sparse coding bands using the dictionary learned from one training band, and its innovation is that patches having the same spatial location of all bands are restricted to be represented using the same atoms. Experimental results based on OMP and K-SVD are provided, which reveal that this proposal has better performance than wavelet based compression algorithm at low bit rates.

optimization of replacement and spare ordering for critical rotary component based on condition signal to date. eksploatacja i niezawodnosc - Maintenance and Reliability 2017; 19 (1): 76-85, http://dx.doi.org/10.17531/ein.2017

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