Distributed feedback (DFB) lasers based on AlGaInAs asymmetric quantum wells (AQWs) have been designed and fabricated. The active region comprises of three 6.4 nm and six 5 nm wells, with +1.3448% compressive strain in quantum wells and -0.7379% tensile strain in barriers. Material quality was characterized by photoluminescence (PL) and photorefletance (PR) investigation. Broadband characteristic was confirmed by a 98 nm wide room temperature PL spectrum centering at 1520 nm. The details of transition energies and their associated quantized energy levels in both types of wells were studied by PR measurement and the results were compared with numerical simulation results and PL spectra. DFB lasers worked in the wavelength range from 1502.8 to 1535.2 nm. Although channels at longer wavelength failed due to process defect in grating, numerical simulation and laser performance analyses indicated that the modal gain of the channel at 1532.2 nm was supported by wide wells.

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Metal wire-grid whose period is far less than the illuminating wavelength exhibits strong polarization selectivity within a large field of view over a wide wave length range. Thus it could be used as the polarization-controller in the polarimetric imaging system. For infrared polarimetric imaging system, an aluminum wire-grid on the CaF substrate with period of 200nm and depth of 100nm was designed based on effective medium theory. The calculation results demonstrate that the designed wire-grid has the extinction ratio larger than 35 dB within a field of view ±20° over both middle wave infrared (MWIR) (3—5 μm) and long wave infrared (LWIR) (8—12 μm). The aluminum wire-grid was fabricated by electron beam lithography, reactive ion etching and plasma stripping. A clear-cut polarimetric image was obtained when wire-grid was placed in front of a MWIR thermal infrared imager.

The dynamics of genuine three-qubit entanglement in Ising spin model is investigated under the effect of a uniform magnetic field with different direction. The analytic expression for the three-tangle measurement is obtained. Results show that the magnetic parameters (direction and magnitude) exert great effect on the entanglement value. The magnetic relative strength has great negative contribution on entanglement. Regardless of the magnitude of external magnetic relative strength, the entanglement value has the minimum, because of the right angle between the spin direction and external magnetic field. Efficient control of the entanglement by appropriate combinations of the tunable parameters should be possible.Keywords Ising model · Entanglement area · Magnetic relative strength Quantum communication has attracted wide spread attention in recent years. It is the most fascinating application of quantum mechanics, and has the potential to outperform its classical counterparts in fidelity and transmission speed. There has been ongoing effort to search for various physical systems that may be propitious to perform quantum communication. Of the various proposals available, the solid state architecture such as those based on electron [1], nuclear spins [2], and those based on superconducting circuits [3] are believed to have the best scalability. Due to the welldefined Hilbert space and the relatively long decoherence time compared to the orbital degrees of freedom, spin is the natural candidate among various microscopic degrees of freedom that have been considered for the role of qubits in solid state QC architectures [4][5][6].The primary resource for solid-state quantum information processing devices [7] mainly depends on the generation of entangled states. Studies on quantum entanglement are the

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