Integration of Ball Lens in Through-Package Via to Enable Photonic Chip-to-Board Coupling

Optical interconnects offer a promising solution to achieve a larger bandwidth distance product, interconnect density and power efficiency compared to their electrical counterparts. The development of a highly efficient and compact interface between CMOS-compatible silicon photonics and board-level optical interconnects can provide a solution to overcome bandwidth-power limitation across chip-to-chip short-reach interconnections for future data centers. In this context, a method to integrate a silicon photonic chip, ball lens embedded package substrate and board-level polymer multimode waveguides has been demonstrated. The development of the involved optical interfaces and corresponding measurement results are reported aided by simulation results. A key outcome of the experiment was a measured 14 micrometre chip-to-package 1dB lateral alignment tolerance for coupling into a 20x24 micrometres squared cross-section board-level polymer multimode waveguide. A 3.4 dB coupling loss across the optical interfaces between the photonic chip output grating and polymer waveguide was measured at a wavelength of 1310 nm.