Glass interposer for heterogeneous integration of flip-chipped photonic and electronic integrated circuits

Abstract

In this Letter, we propose an approach to improve the packaging of electro-optical transceivers based on silicon photonics through the development of a glass interposer. This assembly platform integrates polymer optical waveguides and an integrated turning mirror that vertically redirect the optical signal in the plane of the interposer to the grating coupler of a flip-chipped photonic integrated circuit (PIC). A distinctive feature of the proposed packaging scheme is to use a conventional flip-chip technique without active alignment. Functionalities are completed with a copper redistribution layer that supports the routing of DC to millimeter wave (mmW) signals to drive the PIC. The measured loss in polymer waveguides is 1.92 dB/cm at 1310 nm, and the coupling losses associated with light propagation through the turning mirror and the PIC grating coupler are 18.7 dB. Coplanar mmW waveguides are structured on the glass interposer by cold laser ablation, yielding an attenuation of 0.3 dB/mm at 58 GHz. The most important outcome of this work is that the coupling of the optical signal from the interposer to the PIC is experimentally established. We also assessed the mmW performance of coplanar waveguides through the validation of the interposer to PIC and PIC to the interposer transition.