A two-parameter model of Hermitian matrices in zero-dimensional space is solved in the large-N limit. A very interesting phase diagram and a spontaneous magnetisation are exhibited.

The single transverse mode operation of VCSELs with low threshold current (I th) of 1.5 mA, slope efficiencies about 0.35 W=A, high optical output power of 3.8 mW and speed performance of 10 Gbit=s is reported. The laser has continuous-wave operation and employs oxygen implantation, MOCVD regrowth and selective oxidation on semi-insulating GaAs substrate.

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In this study, the carrier blocking effect on 850 nm InAlGaAs/AlGaAs vertical-cavity surface-emitting layers (VCSELs) was theoretically and experimentally investigated. By means of inserting a high-bandgap electron blocking layer, which was either 10 nm thick Al 0.75 Ga 0.25 As or 13 nm thick Al 0.9 Ga 0.1 As, on the p-side of a quantum-well active region, the laser output performance was theoretically found to be improved. VCSELs with and without an electron blocking layer were also experimentally demonstrated. It was found that the threshold current was reduced from 1.47 to 1.33 mA and the slope efficiency was increased from 0.37 to 0.53 mW mA −1 by inserting a 10 nm thick Al 0.75 Ga 0.25 As electron blocking layer. Also, the device became less sensitive to the device temperature, where the amount of increase in the threshold current at an elevated temperature of 95 • C was only 0.27 mA and the slope efficiency dropped by only 24.5%. A peak frequency response of nearly 9 GHz at 5 mA, measured from relative intensity noise (RIN), was obtained in these VCSEL devices.