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On-chip optical isolation in monolithically integrated non-reciprocal optical resonators


Non-reciprocal photonic devices, including optical isolators and circulators, are indispensible components in optical communication systems. However, the integration of such devices on semiconductor platforms has been challenging because of material incompatibilities between semiconductors and magneto-optical materials that necessitate wafer bonding, and because of the large footprint of isolator designs. Here, we report the first monolithically integrated magneto-optical isolator on silicon. Using a non-reciprocal optical resonator on an silicon-on-insulator substrate, we demonstrate unidirectional optical transmission with an isolation ratio up to 19.5 dB near the 1,550 nm telecommunication wavelength in a homogeneous external magnetic field. Our device has a small footprint that is 290 µm in length, significantly smaller than a conventional integrated optical isolator on a single crystal garnet substrate. This monolithically integrated non-reciprocal optical resonator may serve as a fundamental building block in a variety of ultracompact silicon photonic devices including optical isolators and circulators, enabling future low-cost, large-scale integration.

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Figure 1: Structure and operation principle of the monolithic non-reciprocal optical-resonator-based isolator.
Figure 2: Optical isolation performance of the isolator.
Figure 3: Simulated device performance as a function of SOI waveguide height.
Figure 4: Dispersion relations of the resonance peak shift and FSR of the optical isolator.


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The authors thank Jie Sun for discussions on silicon resonator fabrication. The support of the National Science Foundation and an Intel Fellowship for Lei Bi is gratefully acknowledged.

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Authors and Affiliations



L.B. conducted the theoretical simulation, material fabrication, device fabrication and testing. J.H. conceived the device and contributed to theoretical simulation and device testing. P.J. and D.H.K. contributed to material fabrication. G.F.D., L.C.K. and C.A.R. supervised and coordinated the project. All authors contributed to writing the paper.

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Correspondence to Lei Bi or C. A. Ross.

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The authors declare no competing financial interests.

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Bi, L., Hu, J., Jiang, P. et al. On-chip optical isolation in monolithically integrated non-reciprocal optical resonators. Nature Photon 5, 758–762 (2011).

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