Optical phase modulators are essential to large-scale integrated photonic systems at visible wavelengths and are promising for many emerging applications. However, current technologies require large device footprints and either high power consumption or high drive voltages, limiting the number of active elements in a visible-spectrum integrated photonic circuit. Here, we demonstrate visible-spectrum silicon nitride thermo-optic phase modulators based on adiabatic micro-ring resonators that offer at least a one-order-of-magnitude reduction in both the device footprint and power consumption compared with waveguide phase modulators. Designed to operate in the strongly over-coupled regime, the micro-resonators provide 1.6π phase modulation with minimal amplitude variations, corresponding to modulation losses as small as 0.61 dB. By delocalizing the resonant mode, the adiabatic micro-rings exhibit improved robustness against fabrication variations: compared with regular micro-rings, less than one-third of the power is needed to thermo-optically align the resonances of the adiabatic micro-rings across the chip to the laser frequency.
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The main data supporting the results in this study are available within the paper and its Supplementary Information. The raw datasets generated during the study are too large to be publicly shared, but they are available from the corresponding authors upon reasonable request.
The codes used for conducting full-wave simulations of the adiabatic micro-rings and for acquiring data from integrated photonic chips are available from M.L. and N.Y. upon reasonable request.
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This work was supported by the Defense Advanced Research Projects Agency (grant no. HR00111720034 (G.L., A.M., M.C.S., X.J., M.L. and N.Y.)), the National Science Foundation (grant no. QII-TAQS-1936359 (H.H. and N.Y.) and no. ECCS-2004685 (S.S. and N.Y.)) and the Air Force Office of Scientific Research (grant no. FA9550-14-1-0389 (S.S. and N.Y.) and no. FA9550-16-1-0322 (N.Y.)). A.M. is supported by a Clare Boothe Luce Professorship from the Henry Luce Foundation. M.C.S. acknowledges the support of the 2020 Facebook Fellowship award. M.J.C. is supported by the 2018 SMART Scholarship Program of the US Department of Defense. Device fabrication was carried out at the Columbia Nano Initiative cleanroom, at the Advanced Science Research Center NanoFabrication Facility at the Graduate Center of the City University of New York and at the Cornell NanoScale Science and Technology Facility.
G.L., H.H., M.L. and N.Y. are listed as inventors in a US non-provisional patent application no. 16/838,714, which is related to the technology reported in this article and claims priority to US provisional applications no. 62/838,084 and 62/828,261 filed by Columbia University. The remaining authors declare no competing interests.
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Liang, G., Huang, H., Mohanty, A. et al. Robust, efficient, micrometre-scale phase modulators at visible wavelengths. Nat. Photon. 15, 908–913 (2021). https://doi.org/10.1038/s41566-021-00891-y