A novel design of diffractive optical interconnects for multichip clock distribution

We report a novel system of diffractive optical interconnects for very high speed clock distribution among multichip modules. Our system distributes two clock signals, each from one separate Vertical Cavity Surface Emitting Laser (VCSEL) over four PIN diodes positioned within a radius of 9 mm along a light-guiding glass plate. The incoming optical gaussian beams from VCSEL are splitted by diffractive optical elements into four output beams and the glass plate propagates the light through multiple reflections onto the golden metallized faces towards the detectors. The overall alignment and chromatic acceptance is highly improved by the use of SELFOC micro-lenses that collimate the laser beam onto the diffractive optical element and that focus the output beam onto the active area of the detectors. The proposed architecture allows tolerance on the light source wavelength as high as Δλ = 10 nm and global tolerances of assembly of the glass plate of 1.5 degrees in rotation and 10 µm in translation making it compatible with the processes of hybridization in microelectronics.