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Cited by 253Photonic and Optical DevicesSemiconductor Lasers and Optical DevicesPhotonic Crystals and Applications

3D integration enables ultralow-noise isolator-free lasers in silicon photonics

Open access
Xiang, Chao, Jin, Warren, Terra, Osama, Dong, Bozhang, Wang, Heming, Wu, Lue, Guo, Joel, Morin, Theodore J. +7 more·2023·Nature
DOI 10.1038/s41586-023-06251-wPMC PMC10396957
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Abstract

Photonic integrated circuits are widely used in applications such as telecommunications and data-centre interconnects 1–5 . However, in optical systems such as microwave synthesizers 6 , optical gyroscopes 7 and atomic clocks 8 , photonic integrated circuits are still considered inferior solutions despite their advantages in size, weight, power consumption and cost. Such high-precision and highly coherent applications favour ultralow-noise laser sources to be integrated with other photonic components in a compact and robustly aligned format—that is, on a single chip—for photonic integrated circuits to replace bulk optics and fibres. There are two major issues preventing the realization of such envisioned photonic integrated circuits: the high phase noise of semiconductor lasers and the difficulty of integrating optical isolators directly on-chip. Here we challenge this convention by leveraging three-dimensional integration that results in ultralow-noise lasers with isolator-free operation for silicon photonics. Through multiple monolithic and heterogeneous processing sequences, direct on-chip integration of III–V gain medium and ultralow-loss silicon nitride waveguides with optical loss around 0.5 decibels per metre are demonstrated. Consequently, the demonstrated photonic integrated circuit enters a regime that gives rise to ultralow-noise lasers and microwave synthesizers without the need for optical isolators, owing to the ultrahigh-quality-factor cavity. Such photonic integrated circuits also offer superior scalability for complex functionalities and volume production, as well as improved stability and reliability over time. The three-dimensional integration on ultralow-loss photonic integrated circuits thus marks a critical step towards complex systems and networks on silicon.

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Crossref · 10.1038/s41586-023-06251-w

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  • Modifying the fabrication process to realize delay without sacrificing the performance of other photonic components remains challenging.

    “Modifying the fabrication process without sacrificing the performance of other photonic components remains challenging123.”

    From Roadmapping the next generation of silicon photonics (2024) · cites this paper as [123]

    The section “3D integration of lasers and ultralow-loss PICs” (page unavailable) says that high-temperature processing can violate manufacturing constraints and that subsequent fabrication steps can add waveguide loss. This supports the cited sentence’s concern about preserving photonic performance while changing fabrication processes. The source does not connect that challenge to realizing delay, which appears in the supplied paraphrase but not in the verbatim citing sentence. (LLM, conf=0.84)

    Experimental — accuracy not yet measured

  • Implementing laser-assisted microwave oscillators through silicon photonics with phase noise superior to CMOS-only counterparts requires minimizing the laser noise, PD, and TIA noise.

    “Implementing laser-assisted microwave oscillators through silicon photonics with phase noise superior to CMOS-only counterparts also requires minimizing the laser noise, PD, and TIA noise123.”

    From Roadmapping the next generation of silicon photonics (2024) · cites this paper as [123]

    The ‘Tunable microwave-frequency generation’ section (page not available in our copy) says the microwave signal’s phase noise is determined by laser phase noise, supporting the need to minimize laser noise. It uses a photodiode, but does not say that photodiode or TIA noise must be minimized, or compare phase noise with CMOS-only oscillators. (LLM, conf=0.86)

    Experimental — accuracy not yet measured

  • Engineering of SiN waveguides has reduced the loss to 0.5 dB/m.

    “Engineering of SiN waveguides has reduced the loss to 0.5 dB/m123”

    From Roadmapping the next generation of silicon photonics (2024) · cites this paper as [123]

  • Scaling the photonics and electronics for many emitters and phase shifters, and integrating a considerable delay for the laser and a complex DSP, are both necessary.

    “Scaling the photonics and electronics for many emitters and phase shifters, and integrating a considerable delay121–123 (Fig. 2) for the laser and a complex DSP, are both necessary.”

    From Roadmapping the next generation of silicon photonics (2024) · cites this paper as [123]

    The citation is attached to the claim that a considerable delay must be integrated for the laser. The Methods section on laser self-injection locking describes a short delay line in a measurement interferometer, not a necessary integrated laser delay. A search for long or required laser delay found no passage establishing that requirement. (LLM, conf=0.72)

    Experimental — accuracy not yet measured

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Authors
Xiang, C., Jin, W., Terra, O., Dong, B., Wang, H., Wu, L., Guo, J., Morin, T. J., Hughes, E., Peters, J., Ji, Q.-X., Feshali, A., Paniccia, M., Vahala, K. J., & Bowers, J. E.
Affiliations
  • University of California, Santa Barbara (US)
  • National Institute of Standards and Technology (US)
  • California Institute of Technology (US)
Corresponding author
  • Xiang, Chao
  • Bowers, John E.
ORCID
Venue
Nature
Publisher
Springer Science and Business Media LLC
Published
2023-08-02
Volume
620
Issue
7972
Pages
78-85
ISSN
  • 0028-0836 (ISSN-L)
  • 1476-4687
DOI
10.1038/s41586-023-06251-w
PMC
PMC10396957
OpenAlex
W4385490806
Cited by
253
References
62
Citations by year
2026: 51 · 2025: 98 · 2024: 91 · 2023: 13
FWCI
18.79
Type
journal article
Language
en
Open access
Licence
Locations
  • Nature (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • eScholarship (California Digital Library) (submittedVersion, cc-by)
  • RePEc: Research Papers in Economics (submittedVersion)
Funders
  • Defense Advanced Research Projects Agency (HR0011-20-2-0044, HR0011-22-2-0009)
  • University of California, Santa Barbara
  • Advanced Research Projects Agency
Topics
  • Physical Sciences › Engineering › Electrical and Electronic Engineering › Photonic and Optical Devices
  • Physical Sciences › Engineering › Electrical and Electronic Engineering › Semiconductor Lasers and Optical Devices
  • Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Photonic Crystals and Applications
Keywords
3D integration, silicon photonics, optical isolator, silicon nitride waveguides, monolithic integration, heterogeneous integration, phase noise, high quality factor cavity, microwave synthesizer, photonic integrated circuits

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