Major step towards low-power all-optical switching for optical communications

The January issue of the premier scientific magazine Nature Photonics publishes an ultra-small and fast, electrically pumped all-optical memory on a silicon chip with record low power consumption. This result achieved by imec and its associated laboratory INTEC at the Ghent University, paves the way for optical packet switching with drastically reduced overall power consumption in high-speed, high-data rate optical telecommunication systems.

The optical random access memory has been achieved with ultra-compact micro-disk lasers with a diameter of 7.5µm. The laser light can either propagate in the clockwise or counter clockwise direction and one can switch between these two laser modes using short optical pulses. The lasers, implemented themselves in Indium Phosphide membranes, are heterogeneously integrated onto passive silicon waveguide circuits. This allows to optically interconnect different memory cells using silicon wires. It also allows to use the strongly developed silicon-based microelectronics fabrication technology, making it a cost-effective solution.

Nature Photonics – An ultra-small, low-power, all-optical flip-flop memory on a silicon chip

Ultra-small, low-power, all-optical switching and memory elements, such as all-optical flip-flops, as well as photonic integrated circuits of many such elements, are in great demand for all-optical signal buffering, switching and processing. Silicon-on-insulator is considered to be a promising platform to accommodate such photonic circuits in large-scale configurations. Through heterogeneous integration of InP membranes onto silicon-on-insulator, a single microdisk laser with a diameter of 7.5 µm, coupled to a silicon-on-insulator wire waveguide, is demonstrated here as an all-optical flip-flop working in a continuous-wave regime with an electrical power consumption of a few milliwatts, allowing switching in 60 ps with 1.8 fJ optical energy. The total power consumption and the device size are, to the best of our knowledge, the smallest reported to date at telecom wavelengths. This is also the only electrically pumped, all-optical flip-flop on silicon built upon complementary metal-oxide semiconductor technology.

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