400 fJ/bit silicon ‘transmitter’ uses all CMOS processes

Researchers at Sun Microsystems Physical Sciences Center (San Diego, CA), Sun Laboratories (Menlo, Park, CA), and Luxtera (Carlsbad, CA) have built the lowest-energy-per-bit silicon (Si) communications transmitter (modulator plus driver circuits) to date using all complementary metal-oxide semiconductor (CMOS) processes.

Dec 1st, 2009
Th 400 1109 01

Researchers at Sun Microsystems Physical Sciences Center (San Diego, CA), Sun Laboratories (Menlo, Park, CA), and Luxtera (Carlsbad, CA) have built the lowest-energy-per-bit silicon (Si) communications transmitter (modulator plus driver circuits) to date using all complementary metal-oxide semiconductor (CMOS) processes.

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The key elements of an energy-efficient Si-based interconnect for inter- and intra-chip optical communications are a low-power modulator, a low-power driver circuit, and efficient integration of these two components. For the modulator, the researchers fabricated a ring resonator (15 µm in radius) using the Luxtera-Freescale 130 nm silicon-on-insulator (SOI) CMOS process, with grating couplers used for the optical input and output ports with surface-normal coupling. The modulator was then integrated with a separate driver circuit fabricated in its own CMOS process using flip-chip integration. The hybrid assembly was die-attached and wire-bonded to a printed circuit board and placed on a heat sink for thermal stability. Using an off-chip laser source, stable error-free transmission with a bit-error rate lower than 10-15 at a data rate of 5 Gbit/s was achieved with a power consumption of 1.95 mW, representing a record-low energy consumption of less than 400 fJ/bit. Contact Ashok Krishnamoorthy at ashok.krishnamoorthy@sun.com.

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