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Electrically driven optical isolation through phonon-mediated photonic Autler–Townes splitting


Optical isolators today are exclusively built on magneto-optic principles but are not readily implemented within photonic integrated circuits. So far, no magnetless alternative1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22 has managed to simultaneously combine linearity (that is, no frequency shift), linear response (that is, input–output scaling), ultralow insertion loss and large directional contrast on-chip. Here we demonstrate an electrically driven optical isolator design that leverages the unbeatable transparency of a short, high-quality dielectric waveguide, with the strong attenuation from a critically coupled absorber. Our concept is implemented using a lithium niobate racetrack resonator in which phonon-mediated13 photonic Autler–Townes splitting10,16,23,24 breaks the chiral symmetry of the resonant modes. We demonstrate isolators at wavelengths one octave apart near 1,550 nm and 780 nm, fabricated from the same lithium-niobate-on-insulator wafer. Linear isolation is demonstrated with simultaneously <1 dB insertion loss, >39 dB contrast and 10 dB bandwidth up to ~200 MHz.

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Fig. 1: Optical isolation with a chiral absorber.
Fig. 2: Implementation and characterization of phonon-mediated p-ATS isolator.
Fig. 3: Experimental demonstration of phonon-mediated p-ATS isolators near 1,550 and 780 nm.
Fig. 4: Demonstration of giant isolation using dressed state non-reciprocity.

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Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Code availability

All relevant code is available from the corresponding author upon reasonable request.


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This work was sponsored by the Defense Advanced Research Projects Agency (DARPA) grant FA8650-19-2-7924, the National Science Foundation EFRI grant EFMA-1641084 and the Air Force Office of Scientific Research (AFOSR) grant FA9550-19-1-0256. G.B. additionally acknowledges support from the Office of Naval Research (ONR) Director for Research Early Career grant N00014-17-1-2209 and the Presidential Early Career Award for Scientists and Engineers. D.B.S. acknowledges support from a US National Science Foundation Graduate Research Fellowship. We also thank K. Chow at the Holonyak Micro & Nanotechnology Lab (HMNTL) at the University of Illinois for valuable advice and guidance. The US Government is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding any copyright notation thereon. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of DARPA or the US Government.

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Authors and Affiliations



D.B.S., O.E.Ö. and G.B. jointly conceived the isolator concept. D.B.S. and O.E.Ö. performed the device fabrication, conducted the experimental measurements and analysed the data. All the authors contributed to writing the paper. G.B. supervised all aspects of this project.

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Correspondence to Gaurav Bahl.

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The authors declare no competing interests.

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Peer review informationNature Photonics thanks Chun-Hua Dong and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Figs. 1–5, discussion and Tables 1 and 2.

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Sohn, D.B., Örsel, O.E. & Bahl, G. Electrically driven optical isolation through phonon-mediated photonic Autler–Townes splitting. Nat. Photon. 15, 822–827 (2021).

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