Extending the spectrum of fully integrated photonics
Integrated photonics has profoundly impacted a wide range of technologies underpinning modern society. The ability to fabricate a complete optical system on a chip offers unrivalled scalability, weight, cost and power efficiency. Over the last decade, the progression from pure III-V materials platforms to silicon photonics has significantly broadened the scope of integrated photonics by combining integrated lasers with the high-volume, advanced fabrication capabilities of the commercial electronics industry. Yet, despite remarkable manufacturing advantages, reliance on silicon-based waveguides currently limits the spectral window available to photonic integrated circuits (PICs). Here, we present a new generation of integrated photonics by directly uniting III-V materials with silicon nitride (SiN) waveguides on Si wafers. Using this technology, we present the first fully integrated PICs at wavelengths shorter than silicon's bandgap, demonstrating essential photonic building blocks including lasers, photodetectors, modulators and passives, all operating at sub-um wavelengths. Using this platform, we achieve unprecedented coherence and tunability in an integrated laser at short wavelength. Furthermore, by making use of this higher photon energy, we demonstrate superb high temperature performance and, for the first time, kHz-level fundamental linewidths at elevated temperatures. Given the many potential applications at short wavelengths, the success of this integration strategy unlocks a broad range of new integrated photonics applications.
Additional InformationThe authors thank David Kinghorn for assistance with measurements, Sonya Palmer for fruitful discussion and Lillian McKinney, Brian Long and Yujun Chen for graphic sketches. We are also grateful to Larry Coldren for discussion of high temperature laser performance as well as David Weld and Jianwei Wang for discussion of atomic physics applications. A portion of this work was performed in the UCSB Nanofabrication Facility, an open access laboratory. Part of this work and material (related to UCSB and Caltech) is based upon work supported by the Defense Advanced Research Projects Agency (DARPA) under Contract No. HR001-20-2-0044. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the Defense Advanced Research Projects Agency (DARPA). Author contributions. All devices were designed by H.P., T.K., C.Z. and M.T., and fabricated by C.Z., M.T., W.L. and G.K. Device characterization was performed by H.P, S.B., A.M. and Z.Z. High temperature and noise characterization were performed by T.M., M.T., L.C. and J.G., with the assistance of Z.Y., H.W., B.S. and L.W. Theoretical phase noise investigation was conducted by Z.Y., H.W., B.S. and L.W. The manuscript was prepared by M.T., T.M. and L.C., with the assistance from all of the other authors. T.K. supervised all operations at Nexus Photonics including design, fabrication and characterizations, and L.C., J.B. and K.V. supervised advanced characterization at UCSB and Caltech. Data availability. The data that supports the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request. Code availability. The codes that support the findings of this study are available from the corresponding authors upon reasonable request. Competing interests. J.B. is a cofounder of Nexus Photonics.
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