VCSEL operational requirements for optoelectronic neural networks

Andrew J. Waddie, Mohammad R. Taghizadeh

Research output: Contribution to journalArticlepeer-review


In this paper we shall describe the design and successful operation of an optoelectronic Hopfield network demonstrator system. This demonstrator system, based around a free-space diffractive optical interconnect, was designed to perform a range of optimisation tasks, in particular those associated with the scheduling of packets through different switching topologies. Experimental optimisation of the neural network throughput, for both a crossbar and Banyan switch topology, allows the neural network parameters (e.g. neuron bias, neuron weighting) to be tuned to ensure optimal operation of the network for a particular switch topology. The weighted interconnections in this optoelectronic system are provided by a diffractive optical element/lens combination whilst the neurons are implemented electronically. The transition between the electronic and optical domains is handled by an 8×8 VCSEL array for the electronic-optic interface, and an 8×8 Si photodetector array for the optic-electronic interface. The VCSEL array, supplied by Avalon Photonics, is an oxide-confined near-infrared GaAs device capable of 250MHz modulation at a wavelength of 960nm. The diffractive optical interconnect is designed using simulated annealing optimization and fabricated using VLSI photolithography. Using these techniques it is possible to create interconnects with a total efficiency of ~70% and a uniformity of < 1%.

Original languageEnglish
Pages (from-to)333-344
Number of pages12
JournalProceedings of SPIE - the International Society for Optical Engineering
Publication statusPublished - 2002
EventLaser micromachining for Optoelectronic Device Fabrication - Brugge, Belgium
Duration: 30 Oct 200230 Oct 2002


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