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Supermode control is demonstrated theoretically and experimentally in diffraction-coupled semiconductor laser arrays. A linear theory is presented to determine the supermode threshold gain as a function of the coupling cavity length. By fabricating devices with different coupling cavity lengths, array operation in both the fundamental and highest order supermodes is achieved.

The capture of photoexcited carriers in different laser structures is investigated by subpicosecond luminescence spectroscopy. The capture time at 20 and 80 K is monitored by the decay of the luminescence of the confinement layers. It is found to range between 2 and 3 ps for both linear and parabolic grading, and to be much longer in nongraded structures. The improvement of the capture in the case of graded structures is due to the quasi-electric field experienced by the carriers, and might allow the devices to run at much higher frequencies.

Firstorder gaincoupled (Ga,In)As/(Al,Ga)As distributed feedback lasers by focused ion beam implantation and in situ overgrowth

A GaAs/AlGaAs optical synaptic interconnection device for neural networks is reported for the first time to our knowledge. This device consists of a light-emitting-diode array, an interconnection matrix, and a photodiode array, which are integrated into a hybrid-layered structure on a GaAs substrate. The device structure and characteristics are reported in detail. The fabricated device can simulate a 32-neuron system. Experimental results of the Hopfield associative memory with three stored vectors are also described.

The finite element method was used for calculating the wave functions and energy levels of electrons in arbitrarily shaped two-dimensional quantum-confined structures. The calculated results indicate the possibility of quasi-quantum wires by simply growing single quantum wells on corrugated substrates.

Monolithically integrated surface-emitting device consisting of an AlGaAs/GaAs multiple quantum well distributed feedback laser and a grating coupler is demonstrated for the first time. The grating coupler was made by utilizing the properties of low loss and easily saturable absorption in the multiple quantum well structure. No additional crystal growths or complicated fabrication processes were required for the integration. An output power of 2 mW and a narrow beam divergence of 0.22° were obtained under continuous wave operation.