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Low-loss composite photonic platform based on 2D semiconductor monolayers

Abstract

The optical properties of transition metal dichalcogenides (TMDs) are known to change dramatically with doping near their excitonic resonances. However, little is known about the effect of doping on the optical properties of TMDs at wavelengths far from these resonances, where the material is transparent and therefore could be leveraged in photonic circuits. We demonstrate the strong electrorefractive response of monolayer tungsten disulfide (WS2) at near-infrared wavelengths (deep in the transparency regime) by integrating it on silicon nitride photonic structures to enhance the light–matter interaction with the monolayer. We show that the doping-induced phase change relative to the change in absorption (|∆n/∆k|) is ~125, which is significantly higher than the |∆n/∆k| observed in materials commonly employed for silicon photonic modulators, including Si and III–V on Si, while accompanied by negligible insertion loss.

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Fig. 1: The ionic liquid gated SiN–WS2 platform.
Fig. 2: Change in the complex index of monolayer WS2 at NIR wavelengths.
Fig. 3: Tuning the effective index (Δneff) of the propagating TE and TM modes using monolayer WS2.
Fig. 4: Phase tuning of monolayer TMD using the TMD–HfO2–ITO capacitor.
Fig. 5: Phase tuning of monolayer MoS2 in a composite SiN–MoS2 waveguide.
Fig. 6: Comparison of |∆n/∆k| for various 2D and bulk materials.

Data availability

The experimental dataset and its analysis is provided in the paper and any additional datasets that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

Research on tunable optical phenomena in TMD semiconductors was supported as part of the Energy Frontier Research Center on Programmable Quantum Materials funded by the US Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under award no. DE-SC0019443. Research by I.D. on TMD films for ultrafast and low-power applications was funded by the Defense Advanced Research Projects Agency (DARPA) award nos. HR001110720034 and FA8650-16-7643 and the Air Force Office of Scientific Research (AFOSR) MURI award no. FA9550-18-1-0379. Integration of TMDs with Si photonics for data communications was funded by the Office of Naval Research (ONR) award no. N00014-16-1-2219 and National Aeronautics and Space Administration (NASA) grant no. NNX16AD16G. C.P. and J.P. acknowledge funding from AFOSR (FA9550-16-1-0031 and FA9550-16-1-0347). Y.Y. and L.C. acknowledge support from an EFRI award from NSF (EFMA 1741693). S.H.C. was supported by the Postdoctoral Research Program of Sungkyunkwan University (2016). This work was done in part at the City University of New York Advanced Science Research Center NanoFabrication Facility, in part at the Cornell Nanoscale Facility, supported by NSF award no. EECS-1542081 and in part at the Columbia Nano Initiative (CNI) shared labs at Columbia University in the City of New York. We thank A. Mohanty, C.T. Phare, S.A. Miller and U.D. Dave for fruitful discussions.

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I.D. and M.L. conceived and proposed the TMD-based photonic design and experiments. S.H.C., J.H. and D.N.B. proposed the use of WS2 for these photonic structures. C.P. and J.P. provided the MOCVD WS2 film for the ionic liquid experiments, Y.Y. and L.C. provided the CVD WS2 and MoS2 film for the capacitive device experiments, and S.H.C. and B.L. performed the TMD transferring and characterization (photoluminescence measurements). I.D. fabricated the composite photonic device, with assistance from S.H.C. for TMD processing and development, G.R.B. for ITO development and M.A.T. for the SU-8 cladding of the composite structures. I.D. performed and analysed the optical measurements of the photonic devices. I.D. and G.R.B. performed the capacitance measurements of these structures. I.D. and M.L. prepared the manuscript. S.H.C., D.N.B., J.H. and M.L. edited the manuscript. J.H. and M.L. supervised the project.

Corresponding author

Correspondence to Michal Lipson.

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M.L., J.H., I.D., S.C., G.R.B. and D.N.B are named inventors on US provisional patent application 16/282,013 regarding the technology reported in this article.

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Datta, I., Chae, S.H., Bhatt, G.R. et al. Low-loss composite photonic platform based on 2D semiconductor monolayers. Nat. Photonics 14, 256–262 (2020). https://doi.org/10.1038/s41566-020-0590-4

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