Chemically etched ultrahigh-Q wedge-resonator on a silicon chip

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Ultrahigh-Q optical resonators are being studied across a wide range of fields, including quantum information, nonlinear optics, cavity optomechanics and telecommunications1,2,3,4,5,6,7. Here, we demonstrate a new resonator with a record Q-factor of 875 million for on-chip devices. The fabrication of our device avoids the requirement for a specialized processing step, which in microtoroid resonators8 has made it difficult to control their size and achieve millimetre- and centimetre-scale diameters. Attaining these sizes is important in applications such as microcombs and potentially also in rotation sensing. As an application of size control, stimulated Brillouin lasers incorporating our device are demonstrated. The resonators not only set a new benchmark for the Q-factor on a chip, but also provide, for the first time, full compatibility of this important device class with conventional semiconductor processing. This feature will greatly expand the range of possible ‘system on a chip’ functions enabled by ultrahigh-Q devices.

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Figure 1: Micrographs and mode renderings of the wedge-resonator from top and side views.
Figure 2: Data showing measured Q-factor plotted versus resonator diameter with oxide thickness as a parameter.
Figure 3: Plot of measured FSR versus target design-value resonator diameter on a lithographic mask.
Figure 4: Illustration of tuning control of the SBL devices.
Figure 5: Data plot showing effect of etch time on appearance of the ‘foot’ region in etching of a 10-μm-thick silica layer.


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The authors acknowledge support from the Defense Advanced Research Projects Agency under the iPhoD and Orchid programmes and also the Kavli Nanoscience Institute at Caltech. H.L. acknowledges support from the Center for the Physics of Information, and S.J. thanks the Kwanjeong Educational Foundation.

Author information

All authors made important contributions. H.L., T.C. and J.L. performed measurements and modelling, and contributed equally to the work. H.L. performed microfabrication of devices with assistance from T.C. and K.Y. AFM measurements were performed by H.L. and S.J. The experiments were conceived, designed and planned by H.L., T.C., J.L., O.P. and K.J.V. All authors helped to write the manuscript.

Correspondence to Kerry J. Vahala.

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Lee, H., Chen, T., Li, J. et al. Chemically etched ultrahigh-Q wedge-resonator on a silicon chip. Nature Photon 6, 369–373 (2012) doi:10.1038/nphoton.2012.109

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