Fast electrooptic Bragg grating couplers for on-chip reconfigurable optical waveguide interconnects

We present an array of electrooptic Bragg gratings for on-chip optical waveguide interconnect applications. These integrated gratings can serve as switchable couplers to couple high-speed optical signals from a vertical-cavity surface-emitting laser to on-chip polymeric waveguides and from waveguides to photodetectors. The unique switching feature provides a promising solution to facilitate dynamically reconfigurable on-chip optical interconnects architecture for intrachip, chip-to-chip, and board-to-board data communications. We demonstrate electrooptic grating couplers in a polymeric channel waveguides on a silicon substrate with an electrically tunable surface-normal coupling efficiency up to 8% and a switching speed of 75 μs.

Over THE past decade, the demand for more computing power has increased to such an extent that the multiprocessor system had to be employed in many scenarios. As the processors' speed increase, the electrical interconnects can no longer meet the requirements for high-performance multiprocessor systems [1], [2]. Fig. 1. Schematic of polymeric waveguide interconnect using electrooptic Bragg gratings as fast switchable surface-normal couplers, where high-speed optical signals from VCSELs can be selectively and simultaneously coupled into many photodetectors. The basic limitations of electrical interconnects include transmission bandwidths, clock skews, resistance–capacitance time constants, and fan-in/fan-out capabilities due to the electrical parasitic capacitance, inductance coupling, and electromagnetic wave interference. In an effort to increase the interconnection capability, optical interconnects have been considered as an alternative for quite a long time. Recent development of efficient optoelectronic devices, which include vertical-cavity surface-emitting lasers (VCSELs) and high-speed photodetectors, has stimulated researchers to seek feasible optical solutions [3]. An array of optical interconnects using polymeric waveguides in conjunction with holographic elements have been proposed and demonstrated [4]– [8]. However, these optical interconnects are incapable of providing dynamically reconfigurable interconnection schemes compared to conventional electrical interconnects. Such a problem becomes severe for fast reconfigurable interconnecting architecture when the transmitted bandwidth exceeds 10 Gb/s. Note that the state-of-the-art optical switches have a response time in the range of a few milliseconds.