Photonic Legos of functional 3D thin-films unlock high-performance heterogeneous photonic integration
Photonic integrated circuits route information with optical signals instead of relying only on electrical currents. Silicon (Si) and silicon nitride (SiNx) are excellent photonic platforms for waveguides, but they cannot efficiently perform the ever-increasing tasks required for fully integrated optical systems. A heterogeneous photonic integration platform capable of interfacing different…
Scientists at Washington University in St. Louis, the Swiss Federal Institute of Technology Lausanne and the Massachusetts Institute of Technology have developed a new method for integrating different optical materials to create high-performance heterogeneous photonic integration. This approach overcomes the limitations of conventional heteroepitaxy methods by using van der Waals forces to bond thin-film materials on suitable parent substrates, creating freestanding single-crystalline nanomembranes.
These nanomembranes can then be heterogeneously integrated with other photonic templates to achieve desired optical functionalities. The researchers demonstrated the integration of single-crystalline barium titanate, a ferroelectric material with strong electro-optical properties, onto a silicon photonic chip, resulting in a half-wave voltage-length product of about 0.29 V·cm.
This corresponds to a giant effective Pockels coefficient of about 950 pm/V, which is more than 30 times higher than established electro-optical platform materials. Additionally, they integrated single-crystalline gallium arsenide and gallium nitride nanomembranes onto silicon nitride photonics, expanding the photodetection range from near-ultraviolet to near-infrared wavelengths.
The integration of cobalt ferrite single crystals with silicon microring resonators enabled nonreciprocal optical transmission, while the stacking of barium titanate and cobalt ferrite nanomembranes above a single silicon microring demonstrated the ability to tune light electrically and magnetically within a single multifunctional device.
This vdW integration strategy for 3D thin films offers a flexible platform for synthesizing and integrating freestanding nanomembranes, with potential applications in optical communications, sensing, photonic computing, data storage and quantum technologies.
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