Photonic Chiplet Interconnection via 3D-Nanoprinted Interposer

Huiyu Huang¹, † , Zhitian Shi¹, Giuseppe Talli² , Maxim Kuschnerov² , Richard Penty¹ , and Qixiang Cheng¹,
¹ Centre for Photonic Systems, Electrical Engineering Division, Department of Engineering, University of Cambridge, Cambridge CB3 0FA, UK
² Huawei Technologies Duesseldolf GmbH, European Research Center, Riesstraße 25, 80992 Munich, Duesseldolf, Gemany

Photonic integrated circuits (PICs) have been investigated using a variety of different waveguide materials and each excels in specific key metrics, such as efficient light emission, low propagation loss, high electro-optic efficiency, and potential for volume production. Despite sustained research, each platform shows inherent shortcomings that as a result stimulate studies in hybrid and heterogeneous integration technologies to create more powerful cross-platform devices. This is to combine the best properties of each platform; however, it requires dedicated development of special designs and additional fabrication processes for each different combination of material systems. In this work, we present a novel hybrid integration scheme that leverages a 3D-nanoprinted interposer to realize a photonic chiplet interconnection system. This method represents a generic solution that can readily couple between chips of any material system, with each fabricated on its own technology platform, and more importantly, with no change in the established process flow for the individual chips. Mode-size engineering is enhanced by the off-chip parabolic microreflectors. With a 3D-nanoprinted chip-coupling frame and fiber-guiding funnel, low-loss fully passive assembly and alignment can be achieved. A fast-printing process with submicron accuracy, achieving a mode-field-dimension (MFD) conversion ratio of 5:2 from fiber to chip is demonstrated with a low excess loss of <0.5 dB on top of the 1.7 dB inherent coupling loss. This is, to the best of our knowledge, the largest mode size conversion using non-waveguided components. Furthermore, we demonstrate such a photonic chiplet interconnection system between silicon and InP chips with a 2.5 dB die-to-die coupling loss, across a 140 nm wavelength range between 1480 nm to 1620 nm. This hybrid integration plan can bridge different waveguide materials, supporting a much more comprehensive crossplatform integration.

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