by Clarence Oxford
Los Angeles CA (SPX) Apr 29, 2026
Researchers at Harvard have demonstrated a chip-scale ultraviolet mild supply constructed on thin-film lithium niobate that generates 4.2 milliwatts of on-chip UV energy at 390 nanometers wavelength — roughly 120 instances extra output energy than any earlier comparable demonstration on the identical materials platform.
Ultraviolet mild is used throughout a variety of recent purposes, from floor disinfection and fluorescence imaging of organic supplies to photolithography in semiconductor manufacturing. On the chip scale, compact UV sources are anticipated to allow advances in trapped-ion quantum computer systems, ultra-precise atomic clocks, and compact environmental sensors able to monitoring greenhouse gases and atmospheric pollution.
The core problem has been that UV mild loses energy quickly because it travels by means of optical waveguides, making it extraordinarily troublesome to construct sensible chip-scale sources at these wavelengths. The Harvard crew, working within the lab of Marko Loncar, the Tiantsai Lin Professor of Electrical Engineering, addressed this by changing pink mild to UV mild instantly on the chip moderately than trying to ship UV mild from an exterior supply.
Within the frequency upconversion course of utilized by the machine, two pink photons mix contained in the lithium niobate crystal to supply a single higher-energy UV photon. Lithium niobate is already a well-established platform for built-in photonics, notably at infrared and telecommunications wavelengths, however this work demonstrates it could actually additionally information and host mild sources at a lot shorter UV wavelengths.
“When folks take into consideration [thin-film lithium niobate], they do not consider it as a UV materials, however we present that it’s,” mentioned co-first creator Kees Franken, a former analysis fellow within the Loncar lab. “We additionally present that there are another nonlinear results taking place that we do not totally perceive but.”
Environment friendly frequency conversion in lithium niobate requires a nanofabrication course of referred to as poling, by which the crystal grain buildings are periodically flipped at exactly managed intervals alongside the waveguide. Getting that periodic sample precisely proper — at sub-micron size scales over centimeter-long gadgets — has been the central limitation of earlier makes an attempt.
Earlier fabrication approaches confronted a basic tradeoff. Poling all the movie earlier than etching the waveguides preserved poling high quality however eradicated the flexibility to compensate for fabrication imperfections. Fabricating waveguides first after which poling allowed corrections, however the electrodes needed to be positioned removed from the waveguide, leading to solely partial poling of the movie and diminished conversion effectivity.
The Harvard crew invented a brand new approach they name sidewall poling to resolve this tradeoff. Relatively than putting electrodes solely above the movie, they patterned steel electrodes — formed as slim steel fingers — instantly towards the sidewalls of the etched waveguide, requiring positioning accuracy of roughly 50 nanometers.
“The important thing concept was: might we simply put the electrodes instantly on the waveguide?” mentioned co-first creator Soumya Ghosh, a former graduate pupil within the lab. Inserting electrodes on the sidewalls allowed the researchers to completely invert the crystal domains throughout all the waveguide cross-section, so that each one the sunshine passing by means of the machine sees a uniformly flipped materials construction. This maximizes conversion effectivity all through the waveguide.
The geometry additionally allowed the crew to tailor the poling interval alongside the size of the machine, drawing on tailored poling strategies beforehand developed by the Loncar group and others, to compensate for variations in movie thickness and waveguide form which might be unavoidable in cleanroom fabrication.
Earlier thin-film lithium niobate demonstrations at this wavelength vary produced solely tens of microwatts of UV energy — sufficient to ascertain feasibility however far under the brink for sensible purposes. The brand new machine’s 4.2 milliwatt output represents a step towards real-world usefulness.
Trapped-ion quantum computer systems require exactly managed UV mild at wavelengths comparable to particular atomic transitions, and scaling these techniques all the way down to chip-level elements is taken into account important for making the expertise sensible. “If you would like a scalable quantum laptop that is not the measurement of a truck, you have to scale all the pieces all the way down to the chip degree, and this consists of the sunshine sources,” Franken mentioned.
Ghosh and Franken attributed the advance partially to the Loncar lab’s built-in strategy to analysis, combining theoretical design, cleanroom fabrication, and optical characterization inside a single group. “The hands-on instinct that we gained for how one can make a tool, whereas additionally conserving the zoomed-out view of what this machine is for, and the way we have been going to characterize it — that is an enormous a part of what enabled this mission for us,” Ghosh mentioned.
The paper was co-authored by C.C. Rodrigues, J. Yang, C.J. Xin, S. Lu, D. Witt, G. Joe, G.S. Wiederhecker, and Okay.-J. Boller. Funding got here from the Division of the Air Drive, the Workplace of Naval Analysis, NASA, and the Nationwide Science Basis.
Analysis Report:Milliwatt-level UV era utilizing sidewall poled lithium niobate
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Harvard Faculty of Engineering and Utilized Sciences
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