Integrated photonics has quietly become one of the most consequential technologies of the modern era, carrying the data that flow through data centers, enabling LiDAR systems, and increasingly underpinning quantum information processing. Yet for all its maturity, the field has long been constrained by a deceptively simple problem: no single material can do everything well. Silicon and silicon nitride excel at guiding light with low loss and can be manufactured at scale using the same tools that build computer chips, but they lack the exotic optical properties that modern applications demand. Electro-optic modulation, optical isolation, and broadband photodetection each require materials with specific crystalline and physical properties that cannot be grown directly on silicon or silicon nitride without introducing defects that ruin device performance. A team of researchers led by Sang-Hoon Bae of Washington University in St. Louis, together with collaborators at EPFL, MIT, the University of Illinois Urbana-Champaign, and institutions in Korea and Singapore, now reports in Nature a general solution to this long-standing bottleneck.
The core idea is to sidestep lattice matching altogether. Traditional heteroepitaxy, in which one crystalline material is grown directly on another, runs into severe trouble when the two crystal lattices differ significantly. Strain builds up, dislocations nucleate, and the resulting film quality degrades the very optical properties that made the material attractive in the first place. Instead of growing these functional crystals on photonic substrates, the researchers grow them elsewhere, on compatible native substrates, and then release them as free-standing single-crystalline nanomembranes using advanced epitaxial growth and layer lift-off techniques. These ultrathin membranes, which retain the near-perfect crystal quality of their parent substrate, are then placed onto silicon and silicon nitride photonic chips using what the team calls photonic van der Waals integration, a bonding approach in which weak intermolecular forces hold the membrane in place without demanding any crystallographic registry with the underlying chip.
The versatility of this framework is demonstrated through several flagship devices. The first is an ultraefficient electro-optic modulator built by transferring thin films of barium titanate, a ferroelectric perovskite oxide, onto silicon chips. Barium titanate possesses one of the largest Pockels coefficients of any known material, meaning its refractive index changes dramatically in response to an applied electric field, but exploiting that property on a chip requires careful control of the crystal orientation. The team ensured well-defined crystallographic alignment of the transferred membranes and measured a Pockels coefficient r42 exceeding 1,290 picometers per volt, together with a 3-decibel electro-optic bandwidth above 23 gigahertz. These figures place the modulators among the most efficient ever demonstrated, suggesting that barium titanate could challenge lithium niobate, the current workhorse of high-performance electro-optics, in future integrated photonic circuits.
Modulators are only half the story, however, because practical photonic circuits also need optical isolators, devices that allow light to travel in one direction while blocking it in the other. Isolators protect lasers from back-reflections that would otherwise destabilize them, and they are indispensable in everything from telecom transmitters to quantum photonic systems. On-chip isolation has historically been difficult because the magneto-optic materials with strong Faraday effects, such as yttrium iron garnet, are notoriously hard to integrate with standard platforms. The researchers instead transferred single-crystalline cobalt ferrite nanomembranes into silicon microring resonators, achieving a Faraday rotation coefficient of 33,800 degrees per centimeter, an exceptionally large value that enables ultracompact non-reciprocal devices. By combining the long light-matter interaction path of a resonant cavity with the enormous Faraday response of high-quality cobalt ferrite, the team demonstrated efficient optical isolation in a footprint far smaller than conventional approaches allow.
The third demonstration showcases perhaps the most conceptually striking capability of the technique: stitching different single crystals side by side on a single photonic template. The researchers laterally combined gallium arsenide and gallium nitride single crystals on top of silicon nitride photonics, creating a detector landscape that spans the spectral range from the ultraviolet to the near-infrared. Gallium arsenide, a classic III-V semiconductor, absorbs efficiently in the near-infrared, while gallium nitride, with its wide bandgap, covers the ultraviolet portion of the spectrum. Placing both materials on the same chip, each precisely positioned over the appropriate waveguide structures, effectively gives a photonic circuit multiple eyes tuned to different wavelengths. This kind of spatially programmed material assembly would be essentially impossible to achieve by direct epitaxial growth, where the differing lattice constants and growth chemistries of the two semiconductors would normally force separate fabrication runs or compromise the crystal quality of one or both films.
Taking the concept one step further, the team constructed vertical heterostructures by stacking cobalt ferrite on barium titanate, producing ring resonators that perform electro-optic and magneto-optic modulation simultaneously. In such a device, an applied electric field modulates the phase of light through the Pockels effect in the barium titanate layer, while the magnetic ordering of the cobalt ferrite layer imposes non-reciprocal behavior on the same optical mode. The ability to coalesce multiple functional materials into arbitrary vertical and lateral arrangements points toward photonic circuits in which each region of the chip is dressed with exactly the material functionality it needs, much as modern electronic chips combine transistors, capacitors, and interconnects within a single architecture.
The enabling technology behind all of these demonstrations is the ability to produce and transfer single-crystalline membranes with atomic precision. The team drew on techniques including remote epitaxy, in which a monolayer of graphene between the growth substrate and the growing film allows the film to inherit the substrate’s crystal orientation while remaining weakly attached, and other 2D-materials-based layer transfer methods developed over the past decade. Once grown, the membranes are released and transferred with processes designed to avoid cracks, wrinkles, and contamination, preserving the single-crystal quality that underpins the exceptional electro-optic and magneto-optic coefficients measured in the devices. The authors and their collaborators have previously shown that such approaches can be scaled to wafer dimensions, an essential prerequisite for any manufacturing-relevant technology.
The significance of this work lies less in any single record-breaking device than in the generality of the framework. Previous heterogeneous integration strategies have typically been bespoke, optimized for one material on one platform, with each new combination requiring a fresh engineering campaign. By contrast, photonic van der Waals integration of free-standing nanomembranes is largely agnostic to the specific materials involved, provided they can be grown epitaxially and lifted off. That means ferroelectric oxides, magnetic oxides, III-V semiconductors, and wide-bandgap materials can all be brought to bear on the same silicon and silicon nitride infrastructure that the semiconductor industry already knows how to fabricate at scale. The benchmarking presented in the paper situates these van der Waals-integrated devices favorably against comparable devices made by conventional means, in terms of efficiency, footprint, and bandwidth.
Looking ahead, the researchers suggest that this approach opens new opportunities for advanced hetero-integrated optoelectronic applications and beyond. Data centers continue to demand ever-greater bandwidth and energy efficiency, pushing modulators toward lower drive voltages and higher speeds. Emerging photonic quantum computing platforms require low-loss circuits combined with a rich toolbox of optical nonlinearities and non-reciprocal elements. Compact LiDAR, metrology, and sensing systems would all benefit from chips that can detect across broad spectral ranges without external optics. If single-crystalline nanomembrane integration can be married to existing foundry processes, the photonic equivalent of the materials toolbox that transformed electronics may finally be at hand, letting chip designers choose the best material for every function rather than the best material that happens to grow on the substrate.
Subject of Research: Heterogeneous photonic integration of free-standing single-crystalline functional nanomembranes onto silicon and silicon nitride photonic platforms.
Article Title: Heterogeneous photonic integration of single-crystalline nanomembranes
Article References: Meng, Y., Mao, W., Xu, Z., Jia, D., Lin, M., Seo, J., Kim, B., Zhang, X., Park, E., Lee, S., Kim, J., Han, S., Moon, J.-Y., Xu, W., Zhang, Q., He, X., Chen, M., Nam, S. H., Hu, J., … Bae, S.-H. (2026). Heterogeneous photonic integration of single-crystalline nanomembranes. Nature, 657(8132), 638-645. https://doi.org/10.1038/s41586-026-11000-w
Image Credits: AI Generated
DOI: 10.1038/s41586-026-11000-w
Keywords: photonic integration, nanomembranes, van der Waals integration, barium titanate, cobalt ferrite, electro-optic modulator, optical isolator, silicon photonics, remote epitaxy, gallium arsenide, gallium nitride, photodetectors
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Denise Maddox. (September 23, 2026). Single-Crystal Nanomembranes Unlock a New Era of Photonic Chip Integration. Scienmag. https://scienmag.com/single-crystal-nanomembranes-unlock-a-new-era-of-photonic-chip-integration/
Denise Maddox. “Single-Crystal Nanomembranes Unlock a New Era of Photonic Chip Integration.” Scienmag, 23 September 2026, https://scienmag.com/single-crystal-nanomembranes-unlock-a-new-era-of-photonic-chip-integration/. Accessed 23 September 2026.
Denise Maddox. “Single-Crystal Nanomembranes Unlock a New Era of Photonic Chip Integration.” Scienmag. September 23, 2026. https://scienmag.com/single-crystal-nanomembranes-unlock-a-new-era-of-photonic-chip-integration/
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Tags: advanced photonic device manufacturingbarium titanatebroadband photodetectorscobalt ferritedefect-free crystalline materialselectro-optic modulation materialselectro-optic modulatorgallium arsenidegallium nitrideheteroepitaxy limitationsintegrated photonicslattice mismatch in crystal growthLiDAR system componentsnanomembranesoptical isolatoroptical properties of nanomembranesphotodetectorsphotonic chip integrationphotonic integrationquantum information processingremote epitaxysilicon photonicsSingle-crystal nanomembranesvan der Waals integration
