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Integrated gallium phosphide nonlinear photonics


Gallium phosphide (GaP) is an indirect-bandgap semiconductor used widely in solid-state lighting. Despite numerous intriguing optical properties—including large χ(2) and χ(3) coefficients, a high refractive index (>3) and transparency from visible to long-infrared wavelengths (0.55–11 μm)—its application as an integrated photonics material has been little studied. Here, we introduce GaP-on-insulator as a platform for nonlinear photonics, exploiting a direct wafer-bonding approach to realize integrated waveguides with 1.2 dB cm−1 loss in the telecommunications C-band (on par with Si-on-insulator). High-quality (Q > 105), grating-coupled ring resonators are fabricated and studied. Employing a modulation transfer approach, we obtain a direct experimental estimate of the nonlinear index of GaP at telecommunication wavelengths: n2 = 1.1(3) × 10−17 m2 W−1. We also observe Kerr frequency comb generation in resonators with engineered dispersion. Parametric threshold powers as low as 3 mW are realized, followed by broadband (>100 nm) frequency combs with sub-THz spacing, frequency-doubled combs and, in a separate device, efficient Raman lasing. These results signal the emergence of GaP-on-insulator as a novel platform for integrated nonlinear photonics.

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Fig. 1: GaP as a material for integrated nonlinear photonics.
Fig. 2: GaP waveguide resonators.
Fig. 3: Linear and nonlinear response of a GaP microresonator.
Fig. 4: GaP microresonator frequency combs.

Data availability

Data supporting the plots within this paper and other findings of this study are available through Zenodo at Further information is available from the corresponding authors upon reasonable request.

Code availability

Simulation code supporting the plots within this paper and other findings of this study are available through Zenodo at Further information is available from the corresponding authors upon reasonable request.


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We thank P. Welter, H. Hahn, U. Drechsler, D. Caimi and A. Olziersky for their valuable contributions to development of the GaP-on-insulator platform. We also thank M. Karpov and T. Herr for useful discussions about frequency comb generation. This work was supported by the European Union’s Horizon 2020 Programme for Research and Innovation under grants 722923 (Marie Curie H2020-ETN OMT) and 732894 (FET Proactive HOT). All samples were fabricated at the Binnig and Rohrer Nanotechnology Center (BRNC) at IBM Research – Zurich.

Author information




K.S. and P.S. developed the GaP-on-insulator platform with support from S.H., Y.B. and L.C. S.H. fabricated all devices used in the reported experiments, took SEM and atomic force microscopy images and performed Raman measurements. D.J.W. conducted microresonator experiments and analysed data with support from K.S., S.H., M.A. and P.S. M.A. carried out all numerical simulations for the project, in addition to providing general theory support. D.J.W. wrote the manuscript with support from all co-authors. T.J.K. guided the investigation of frequency combs. P.S. conceived and oversaw the project.

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Correspondence to Tobias J. Kippenberg or Paul Seidler.

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Wilson, D.J., Schneider, K., Hönl, S. et al. Integrated gallium phosphide nonlinear photonics. Nat. Photonics 14, 57–62 (2020).

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