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HISTORIC aims to develop and test complex photonic integrated circuits containing a relatively large number
of digital photonic elements for use in e.g. all-optical packet switching. These photonic digital units are alloptical
flip-flops based on ultra compact laser diodes, such as microdisk lasers and photonic crystal lasers.
These lasers are fabricated making use of the heterogeneous integration of InP membranes on top of silicon
on insulator (SOI) passive optical circuits. The very small dimensions of the lasers are, at least for some
approaches, possible because of the high index contrast of the InP membranes and by making use of the
extreme accuracy of CMOS processing.
All-optical flip-flops based on heterogeneously integrated microdisk lasers with diameter of 7.5μm have
already been demonstrated. They operate with a CW power consumption of a few mW and can switch in 60ps
with switching energies as low as 1.8 fJ. Their operation as all-optical gate has also been demonstrated.
Work is also on-going to fabricate heterogeneously integrated photonic crystal lasers and all-optical flip-flops
based on such lasers. A lot of attention is given to the electrical pumping of the membrane InP-based photonic
crystal lasers and to the coupling to SOI wire waveguides. Optically pumped photonic crystal lasers coupled
to SOI wires have been demonstrated already.
The all-optical flip-flops and gates will be combined into more complex photonic integrated circuits,
implementing all-optical shift registers, D flip-flops, and other all-optical switching building blocks.
The possibility to integrate a large number of photonic digital units together, but also to integrate them with
compact passive optical routers such as AWGs, opens new perspectives for the design of integrated optical
processors or optical buffers. The project therefore also focuses on designing new architectures for such
optical processing or buffer chips.
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