Many properties of an optically interconnected system can be improved through the use of a modelocked laser. The short pulse duration, high peak power, wide spectral bandwidth, and low timing jitter of such a laser lead to these benefits. Timing advantages include simplified synchronization across large chip areas, receiver latency reduction, and data resynchronization. Lower power dissipation may be achieved through improved receiver sensitivity. Additional applications of short optical pulses include time-division multiplexing, single-source wavelength-division multiplexing, and precise time-domain testing of circuits. Several of these concepts were investigated using a high-speed chip-to-chip optical interconnect demonstration link. The link employs a modelocked laser and surface-normal optoelectronic modulators that were flip-chip bonded to silicon CMOS circuits. This paper outlines experiments that were performed on or simulated for the link, and discusses the important benefits of ultrashort optical pulses for optical interconnection.

We demonstrate the use of a 30-period dielectric stack structure as a highly dispersive device to spatially separate two beams with a 4-nm wavelength difference by more than their beam width. Unlike previous devices, our structure is simple to fabricate and relatively compact. We discuss possible applications of our device within wavelength-division multiplexing systems.

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We demonstrate operation of a wavelength division multiplexed chip-to-chip optical interconnect using surfacenormal electroabsorption modulators, and a modelocked laser as a single broadband source. The link was successfully operated at 80 Mb/s. While this rate was limited by the repetition rate of the modelocked source, individual CMOS circuits and optoelectronic devices have been shown to work at data rates approaching 1 Gb/s.

Abstract-We present the first measurements of opticalelectrical-optical conversion latency in a hybridly-integrated optoelectronic/silicon complementary metal-oxide-semiconductor (CMOS) chip designed for optical interconnection. Using an optical pump-probe technique, we perform precise measurements with picosecond resolution that closely match our simulations. Our findings suggest that optical interconnects have the potential to provide equal or lower latency than on-chip global wires in future CMOS microelectronics.