Optomechanical Monte Carlo Tolerancing Study of a Packaged Free-Space Intra-MCM Optical Interconnect System

Abstract

We report on the performance of an intra-multichip-module free-space optical interconnect that integrates microlenses and a deflection prism above a dense optoelectronic chip, under various fabrication and assembly errors. This paper describes the results of a combination of mechanical Monte Carlo analysis and optical simulations. Both the technological requirements to ensure a high process yield, and the specifications of the technology we use at our laboratories to fabricate the microoptical and micromechanical components, deep lithography with protons (DLP), are discussed. Therefore, we first conduct a sensitivity analysis that is subsequently used to set the variances of the random perturbations of the Monte Carlo simulation. By scaling these variances, we are able to investigate the effect of a technology accuracy enhancement on the fabrication and assembly yield. We estimate that 40% of the systems fabricated with DLP will show an optical transmission efficiency above -4.32 dB, which is -3.02 dB below the theoretical obtainable value. In this paper, we also discuss our efforts to implement an optomechanical Monte Carlo simulator. It allows us to deal with specific issues not directly related with the microoptical or DLP components, such as the influence of gluing layers and structures that allow for self-alignment, by combining mechanical tolerancing algorithms with optical simulation software. In particular, we determine that DLP provides ample accuracy to meet the requirements of a high manufacturing yield (around 91% meet an optical transmission that is -0.75 dB below the theoretical maximum). The adhesive bonding of optoelectronic devices in their package, however, is subject to further improvement to enhance the tilt accuracy of the devices with respect to the optical interconnect modules