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Low-power integrated optical amplification through second-harmonic resonance

Nature volume 649, pages 1159–1164 (2026)Cite this article

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Abstract

Optical amplifiers are fundamental to modern photonics, enabling long-distance communications1, precision sensing2,3 and quantum information processing4,5. Erbium-doped amplifiers dominate telecommunications but are restricted to specific wavelength bands1,6, whereas semiconductor amplifiers offer broader coverage but suffer from high noise and nonlinear distortions7. Optical parametric amplifiers (OPAs) promise broadband, quantum-limited amplification across arbitrary wavelengths8. However, their miniaturization and deployment have been hampered by watt-level power requirements. Here we demonstrate an integrated OPA on thin-film lithium niobate that achieves >17 dB gain with <200 mW input power—an order of magnitude improvement over previous demonstrations. Our second-harmonic-resonant design enhances both pump generation efficiency (95% conversion) and pump power utilization through recirculation, without sacrificing bandwidth. The resonant architecture increases the effective pump power by nearly an order of magnitude compared with conventional single-pass designs, while also multiplexing the signal and pump. We demonstrate flat near-quantum-limited noise performance over 110 nm. Our low-power architecture enables practical on-chip OPAs for next-generation quantum and classical photonics.

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Fig. 1: Integrated optical parametric amplification and SH resonant design.
Fig. 2: Resonant SH generation.
Fig. 3: SH-resonant optical parametric amplification measurements.
Fig. 4: OPA noise figure measurements.

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Data availability

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

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Acknowledgements

This work was supported in part by the Defense Advanced Research Projects Agency (DARPA) INSPIRED programme (HR00112420356). Part of this work was performed at the Stanford Nano Shared Facilities (SNSF) and the Stanford Nanofabrication Facility (SNF), supported by the National Science Foundation under award ECCS-2026822. We also thank NTT Research for their financial and technical support. D.J.D. acknowledges support from the NSF GRFP (DGE-1656518). H.S.S. acknowledges support from the Urbanek Family Fellowship. L.Q. gratefully acknowledges support from the Shoucheng Zhang Graduate Fellowship Program. We are grateful for the discussions with J. Kahn, D. Serkland at Sandia, J. Cohen at DARPA, G. H. Ahn and K. Multani.

Author information

Author notes

  1. These authors contributed equally: Devin J. Dean, Taewon Park

Authors and Affiliations

  1. Department of Applied Physics and Ginzton Laboratory, Stanford University, Stanford, CA, USA

    Devin J. Dean, Taewon Park, Hubert S. Stokowski, Luke Qi, Sam Robison, Alexander Y. Hwang, Jason F. Herrmann, Martin M. Fejer & Amir H. Safavi-Naeini

  2. Department of Electrical Engineering, Stanford University, Stanford, CA, USA

    Taewon Park

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Contributions

D.J.D. and A.H.S.-N. conceived the idea; D.J.D. designed the device, with input from T.P. and H.S.S.; T.P. fabricated the devices, with assistance from D.J.D., L.Q., S.R., A.Y.H. and J.F.H.; D.J.D. performed the experiments and analysed the data; H.S.S., T.P., M.M.F. and A.H.S.-N. provided the experimental and theoretical support.

Corresponding author

Correspondence to Amir H. Safavi-Naeini.

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Competing interests

D.J.D., T.P., H.S.S. and A.H.S.-N. are inventors on a patent application that covers methods for achieving quantum advantage in power-constrained photonic sensors. The other authors declare no competing interests.

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Nature thanks Wenzhao Sun and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

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Extended data figures and tables

Extended Data Fig. 1 Chip-scale broadband OPA demonstrations.

(a) Gain versus pump power for chip-scale OPAs in the literature (see Extended Data Table 1). Green circles represent phase-insensitive amplification measurements and red squares phase-sensitive amplification. Darker points correspond to data from this work (see Fig. 3). Curves are simulations using the same parameters as Section III. (b) Gain rate (at max reported power) vs loss rate of chip-scale OPAs. Dashed lines are lines of constant nonlinearity-to-loss ratio. Those references that did not include loss rate information could not be plotted.

Extended Data Fig. 2 Broadband gain and noise spectra.

(a) OPA gain spectrum for a L = 6 mm device. Inset: OPA gain spectrum as predicted by simulated dispersion. (b) Spontaneous parametric fluorescence spectrum verifying bandwidth exceeds 150 nm.

Extended Data Fig. 3 Gain measurements at various on-chip input powers.

(a) Phase-insensitive gain from OPA and corresponding FH pump depletion from SHG for nondegenerate signal wavelength 1590 nm and on-chip FH pump powers 38 mW and 194 mW. (b) Phase-sensitive gain from OPA and corresponding FH pump depletion from SHG for degenerate signal wavelengths for on-chip pump powers of 15 mW and 65 mW.

Extended Data Fig. 4 Extracting noise figure from SPF spectrum.

(a) Signal and generated idler measured with the max-hold technique (circles), as well as spectrum for a single signal wavelength input (solid line). (b) Degenerate amplification spectra. SPF level is extracted from off-degenerate reading, and the gain is extracted not from this single scan but instead by measuring the amplification/deamplification cycles in time as in Fig. 4(c).

Extended Data Fig. 5 Dichroic coupler characterization.

(a) Microscope Image of fabricated dichroic coupler (0.5 mm straight coupling region is cropped out, left half reflected and shown for clarity). (b) Transmission spectra of dichroic coupler drop (top) and through (bottom) ports. (c) Simulated symmetric mode profiles of fundamental and second harmonic in coupler region.

Extended Data Fig. 6 Fiber inputs and outputs to chip.

Microscope image of fibers coupling light onto and off of the chip. Lensed single mode fiber (top left and bottom right) couple light onto the chip, while lensed multi-mode fiber (bottom left and top right) collect light from the chip.

Extended Data Fig. 7 On-chip transmission spectrum and end-facet reflections.

(a) On-chip signal transmission spectrum through device. Smoothed line also shown to guide the eye. (b) Inset: zoom in on sinusoidal ripples due to end-facet reflections on either side of the chip, creating a weak standing-wave cavity. (c) Simulated amplified signal transmission in the presence of facet reflections, for gains ranging from 0 to 20 dB. The gain ripples increase close to threshold, where net gain approaches net round-trip loss.

Extended Data Fig. 8 Fabrication procedure.

(a) Deposit 100 nm of SiO2 onto thin-film lithium niobate on insulator chip. (b) Use electron beam lithography to pattern and then liftoff 100 nm-thick aluminum electrodes where the poling periods are adaptively designed to compensate for thickness variations across the film. (c) Apply high voltage pulses to periodically pole the LN and then remove the electrodes. (d) Pattern HSQ mask using electron beam lithography for waveguide patterning. (e) Argon ion mill 300 nm of LN to etch the waveguides and then acid cleaning to produce patterned LN waveguides. (f) Deposit 700 nm of SiO2 for cladding using HDPCVD.

Extended Data Table 1 Chip-scale broadband OPA demonstrations
Full size table

Supplementary information

Supplementary Information

This file contains additional information on SH-resonant SHG calculations, gain and noise figure equations used in data analysis and a brief comment on saturation effects.

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Dean, D.J., Park, T., Stokowski, H.S. et al. Low-power integrated optical amplification through second-harmonic resonance. Nature 649, 1159–1164 (2026). https://doi.org/10.1038/s41586-025-09959-z

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