Abstract
Due to their high optical transparency and electrical conductivity, indium tin oxide thin films are a promising material for photonic circuit design and applications. However, their weak optical nonlinearity has been a substantial barrier to nonlinear signal processing applications. In this study, we show that an atomically thin (~1.5 nm) indium tin oxide film in the form of an air/indium tin oxide/SiO2 quantum well exhibits a second-order susceptibility χ2 of ~1,800 pm V–1. First-principles calculations and quantum electrostatic modelling point to an electronic interband transition resonance in the asymmetric potential energy of the quantum well as the reason for this large χ2 value. As the χ2 value is more than 20 times higher than that of the traditional nonlinear LiNbO3 crystal, our indium tin oxide quantum well design can be an important step towards nonlinear photonic circuit applications.
This is a preview of subscription content, access via your institution
Access options
Access Nature and 54 other Nature Portfolio journals
Get Nature+, our best-value online-access subscription
$29.99 / 30 days
cancel any time
Subscribe to this journal
Receive 12 print issues and online access
$259.00 per year
only $21.58 per issue
Buy this article
- Purchase on Springer Link
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
Data availability
All related data generated and/or analysed in this study are available from the corresponding authors on reasonable request. Source data are provided with this paper.
References
Rogers, C. et al. A universal 3D imaging sensor on a silicon photonics platform. Nature 590, 256–261 (2021).
Bai, B. et al. Microcomb-based integrated photonic processing unit. Nat. Commun. 14, 66 (2023).
Liu, J. et al. Research progress in optical neural networks: theory, applications and developments. PhotoniX 2, 5 (2021).
Zuo, Y. et al. All-optical neural network with nonlinear activation functions. Optica 6, 1132–1137 (2019).
Hazan, A. et al. MXene-nanoflakes-enabled all-optical nonlinear activation function for on-chip photonic deep neural networks. Adv. Mater. 35, 2210216 (2023).
Solntsev, A. S., Agarwal, G. S. & Kivshar, Y. S. Metasurfaces for quantum photonics. Nat. Photon. 15, 327–336 (2021).
Qian, H. et al. Large optical nonlinearity enabled by coupled metallic quantum wells. Light Sci. Appl. 8, 13 (2019).
Zhong, H.-S. et al. 12-Photon entanglement and scalable scattershot boson sampling with optimal entangled-photon pairs from parametric down-conversion. Phys. Rev. Lett. 121, 250505 (2018).
Ergoktas, M. S. et al. Multispectral graphene-based electro-optical surfaces with reversible tunability from visible to microwave wavelengths. Nat. Photon. 15, 493–498 (2021).
Nauman, M. et al. Tunable unidirectional nonlinear emission from transition-metal-dichalcogenide metasurfaces. Nat. Commun. 12, 5597 (2021).
Song, Y. et al. Nonlinear few-layer antimonene-based all-optical signal processing: ultrafast optical switching and high-speed wavelength conversion. Adv. Opt. Mater. 6, 1701287 (2018).
Capretti, A., Wang, Y., Engheta, N. & Dal Negro, L. Comparative study of second-harmonic generation from epsilon-near-zero indium tin oxide and titanium nitride nanolayers excited in the near-infrared spectral range. ACS Photon. 2, 1584–1591 (2015).
Rosencher, E. et al. Quantum engineering of optical nonlinearities. Science 271, 168–173 (1996).
Jang, J., Kang, Y., Cha, D., Bae, J. & Lee, S. Thin-film optical devices based on transparent conducting oxides: physical mechanisms and applications. Crystals https://doi.org/10.3390/cryst9040192 (2019).
Jin, S. et al. Tuning the properties of transparent oxide conductors. Dopant ion size and electronic structure effects on CdO-based transparent conducting oxides. Ga- and In-doped CdO thin films grown by MOCVD. Chem. Mater. 20, 220–230 (2008).
Ma, Z., Li, Z., Liu, K., Ye, C. & Sorger, V. J. Indium-tin-oxide for high-performance electro-optic modulation. Nanophoton. 4, 198–213 (2015).
Peng, Z., Chen, X., Fan, Y., Srolovitz, D. J. & Lei, D. Strain engineering of 2D semiconductors and graphene: from strain fields to band-structure tuning and photonic applications. Light Sci. Appl. 9, 190 (2020).
Dong, Z. et al. Second-harmonic generation from sub-5 nm gaps by directed self-assembly of nanoparticles onto template-stripped gold substrates. Nano Lett. https://doi.org/10.1021/acs.nanolett.5b02109 (2015).
Li, S.-Q. et al. Dramatically enhanced second harmonic generation in Janus group-III chalcogenide monolayers. Adv. Opt. Mater. 10, 2200076 (2022).
Alam, M., De Leon, I. & Boyd, R. Large optical nonlinearity of indium tin oxide in its epsilon-near-zero region. Science https://doi.org/10.1126/science.aae0330 (2016).
Butet, J., Brevet, P.-F. & Martin, O. J. F. Optical second harmonic generation in plasmonic nanostructures: from fundamental principles to advanced applications. ACS Nano 9, 10545–10562 (2015).
De Liberato, S. Light-matter decoupling in the deep strong coupling regime: the breakdown of the Purcell effect. Phys. Rev. Lett. 112, 016401 (2014).
Datta, R. S. et al. Flexible two-dimensional indium tin oxide fabricated using a liquid metal printing technique. Nat. Electron. 3, 51–58 (2020).
Li, Q. et al. Gas-mediated liquid metal printing toward large-scale 2D semiconductors and ultraviolet photodetector. npj 2D Mater. Appl. https://doi.org/10.1038/s41699-021-00219-y (2021).
Jannat, A. et al. Printable single-unit-cell-thick transparent zinc-doped indium oxides with efficient electron transport properties. ACS Nano 15, 4045–4053 (2021).
Lin, K.-Q. et al. Twist-angle engineering of excitonic quantum interference and optical nonlinearities in stacked 2D semiconductors. Nat. Commun. 12, 1553 (2021).
Eckardt, R. & Reintjes, J. Phase matching limitations of high efficiency second harmonic generation. IEEE J. Quantum Electron. 20, 1178–1187 (1984).
Lahon, S., Jha, P. K. & Mohan, M. Nonlinear interband and intersubband transitions in quantum dots for multiphoton photodetectors. J. Appl. Phys. 109, 054311 (2011).
Aukarasereenont, P. et al. Liquid metals: an ideal platform for the synthesis of two-dimensional materials. Chem. Soc. Rev. https://doi.org/10.1039/d1cs01166a (2022).
Schmidt, P. et al. Nano-imaging of intersubband transitions in van der Waals quantum wells. Nat. Nanotechnol. 13, 1035–1041 (2018).
Boyd, R. W. Nonlinear Optics 3rd edn (Academic Press, 2008).
Bennett, H. S. Heavy doping effects on bandgaps, effective intrinsic carrier concentrations and carrier mobilities and lifetimes. Solid-State Electron. 28, 193–200 (1985).
Shen, Y., Lou, Y., Wang, Z. & Xu, X. In-situ growth and characterization of indium tin oxide nanocrystal rods. Coatings https://doi.org/10.3390/coatings7120212 (2017).
Yu, W. J. et al. Unusually efficient photocurrent extraction in monolayer van der Waals heterostructure by tunnelling through discretized barriers. Nat. Commun. 7, 13278 (2016).
Guo, X. et al. Parametric down-conversion photon-pair source on a nanophotonic chip. Light Sci. Appl. 6, e16249 (2017).
Liu, M. et al. A graphene-based broadband optical modulator. Nature 474, 64–67 (2011).
Timurdogan, E., Poulton, C. V., Byrd, M. J. & Watts, M. R. Electric field-induced second-order nonlinear optical effects in silicon waveguides. Nat. Photon. 11, 200–206 (2017).
Shree, S. et al. Interlayer exciton mediated second harmonic generation in bilayer MoS2. Nat. Commun. 12, 6894 (2021).
Breunig, I. Three-wave mixing in whispering gallery resonators. Laser Photon. Rev. 10, 569–587 (2016).
Yu, S., Wu, X., Wang, Y., Guo, X. & Tong, L. 2D materials for optical modulation: challenges and opportunities. Adv. Mater. 29, 1606128 (2017).
Khan, A. R. et al. Optical harmonic generation in 2D materials. Adv. Funct. Mater. 32, 2105259 (2022).
Basov, D. N., Fogler, M. M. & García de Abajo, F. J. Polaritons in van der Waals materials. Science 354, aag1992 (2016).
Wu, Z.-J. et al. Nonlinear plasmonic frequency conversion through quasiphase matching. Phys. Rev. B https://doi.org/10.1103/PhysRevB.82.155107 (2010).
Riemensberger, J. et al. A photonic integrated continuous-travelling-wave parametric amplifier. Nature 612, 56–61 (2022).
Setzpfandt, F. et al. Tunable generation of entangled photons in a nonlinear directional coupler. Laser Photon. Rev. 10, 131–136 (2016).
Yin, P. et al. 2D materials for nonlinear photonics and electro-optical applications. Adv. Mater. Interfaces 8, 2100367 (2021).
Li, Y. et al. Giant two-photon absorption in monolayer MoS2. Laser Photon. Rev. 9, 427–434 (2015).
Erhart, P., Klein, A., Egdell, R. G. & Albe, K. Band structure of indium oxide: indirect versus direct band gap. Phys. Rev. B 75, 153205 (2007).
Lin, J.-J. & Li, Z.-Q. Electronic conduction properties of indium tin oxide: single-particle and many-body transport. J. Phys. Condens. Matter 26, 343201 (2014).
Varley, J. B. & Schleife, A. Bethe–Salpeter calculation of optical-absorption spectra of In2O3 and Ga2O3. Semicond. Sci. Technol. https://doi.org/10.1088/0268-1242/30/2/024010 (2015).
Tang, Y. L., Huang, C. H. & Nomura, K. Vacuum-free liquid-metal-printed 2D indium-tin oxide thin-film transistor for oxide inverters. ACS Nano 16, 3280–3289 (2022).
Blaha, P. et al. WIEN2k: an APW+lo program for calculating the properties of solids. J. Chem. Phys. 152, 074101 (2020).
Acknowledgements
The work at Zhejiang University was sponsored by the National Key Research and Development Program of China under grant no. 2021YFB2801801 and the National Natural Science Foundation of China (NNSFC) under grant nos 62005237 and 62175217. We acknowledge the Zhejiang University Micro-Nano Fabrication Center for providing the facilities and assistance.
Author information
Authors and Affiliations
Contributions
H.Q. conceived the idea. Y.Z. conducted the theoretical modelling and optical measurements. B.G., Y.T. and P.W. performed the material fabrication and characterization. Y.Z., B.G., D.L. and H.Q. contributed extensively to the writing of the manuscript. Y.Z., B.G., D.L., W.X., J.N., Y.F., H.C. and H.Q. analysed data and interpreted the details of the results. H.C. and H.Q. supervised the research.
Corresponding authors
Ethics declarations
Competing interests
The authors declare no competing interests.
Peer review
Peer review information
Nature Nanotechnology thanks Kai-Qiang Lin and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
Additional information
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary information
Supplementary Information
Supplementary Figs. 1–14, Notes 1–15 and Tables 1 and 2.
Source data
Source Data Fig. 1
Calculated dipole moment and measured reflectance data for different ITO/substrate samples.
Source Data Fig. 2
AFM data and optical measurement for 2D ITO.
Source Data Fig. 3
Second-order-nonlinearity-related optical measurement data for 2D ITO.
Source Data Fig. 4
Energy level number relation for ITO-based QW and wavelength- and angle-dependent optical measurements.
Rights and permissions
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
About this article
Cite this article
Zhang, Y., Gao, B., Lepage, D. et al. Large second-order susceptibility from a quantized indium tin oxide monolayer. Nat. Nanotechnol. 19, 463–470 (2024). https://doi.org/10.1038/s41565-023-01574-1
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/s41565-023-01574-1