A new blue fluorescent molecule set new top emission efficiencies in both solid and liquid states, according to a University of Michigan-led study that could pave the way for applications in technology and medicine.&nbsp;Able to absorb light and emit it at lower energy levels, fluorescent molecules called fluorophores glow in OLED displays and help doctors and scientists figure out what’s happening in cells and tissues. They need to be solid in displays and many sensing applications, but liquids are typically preferred for biological uses. Most fluorophores don’t work well in both forms, but this one does.“The fluorescent material reached record-breaking brightness and efficiency with 98% quantum efficiency in the solid state and 94% in solution,” said <a href="https://mse.engin.umich.edu/people/jinsang" target="_blank" rel="noreferrer noopener">Jinsang Kim</a>, the Raoul Kopelman Collegiate Professor of Science and Engineering in the U-M Department of Materials Science and Engineering who led the study, which is published in Nature Communications.Often, engineers designing fluorophores start in solution, exploring the optical properties of individual molecules, but run into problems in their solid-state applications when fluorophore molecules contact each other.&nbsp;“Fluorophores behave very differently in the solid state, which then requires more rational molecular engineering effort for structural modification,” Kim said “By investigating and establishing a molecular design principle to make fluorophores that are bright both in solution and solid states, we have reduced development time and cost for various future applications.”The initial discovery of the versatile fluorophore—called TGlu for short—was unexpected for lead author <a href="https://www.linkedin.com/in/jungmoo-heo-4479351bb/" target="_blank" rel="noreferrer noopener">Jung-Moo Heo</a>, U-M postdoctoral research fellow of materials science and engineering.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1751417438256-TGlu_Liquid-Solid-featured.v1.jpg" style="width: 100%px;" class="fr-fic fr-dib">The new TGlu molecule is a small but powerful single benzene fluorophore with a quantum yield—percent light re-emitted versus light lost as heat—above 90% in both solution and solid. Caption. Credit: Jinsang Kim Laboratory.“TGlu was an intermediate step for another chemical design, but during purification I found it was surprisingly highly emissive, not only in solution but also in solid state,” Heo said.&nbsp;The discovery led to the systematic study to establish the optimal design. The result was a simple design: a single benzene ring core—six carbon atoms joined in a hexagon. The researchers positioned two groups that give away electrons, called donor groups, across the ring from one another. Next to the donors, they placed two acceptor groups, which withdraw electrons, across the ring from one another.&nbsp;“This so-called quadrupolar structure symmetrically distributes charge across the molecule, providing stable emission in various environments,” Heo said.Because the ring has only six points, donor and acceptor groups are positioned next to each other. This spatial arrangement reduces the energy gap compared to other similar molecules within a compact framework, which means the fluorophore needs a relatively small amount of energy to move an electron from the ground state to an excited state—similar to jumping up a rung on a ladder. &nbsp;However, the molecule’s small size means overall conjugation length remains limited—meaning electrons cannot spread out too far across the molecule. This keeps the absolute energy gap—the distance between ladder rungs—wide enough to emit blue light instead of shifting towards narrower energy gap colors like red.&nbsp;Typically, small band gaps come with an efficiency drawback. When in the excited state on the higher rung of the ladder, an electron can either emit light as it comes back down to the ground state or lose energy as heat through vibration. Often, small band gaps mean more heat loss, reducing the quantum yield—an efficiency metric expressed as the percentage of absorbed UV light that gets reemitted as visible light relative to the amount lost as heat.&nbsp;After trying a series of acceptor groups, the researchers found one that stabilizes the excited state. Even with the small band gap, this acceptor group prevents heat loss by restricting access to what are known as conical intersections, which function as “exit doors” for energy leakage. This unexpected behavior, called an Inverted Energy Gap Law, was confirmed both by experiments and quantum chemical simulations.In the solid state, the acceptor groups, which were intentionally designed to be bulky, prevent the molecules from getting too close to one another which causes fluorophores to lose brightness as energy escapes as heat instead of light, a phenomenon known as quenching.The small, highly-efficient fluorophore is simple to produce—only requiring three steps—which increases its scalability while reducing production costs.The current TGlu design fluoresces blue light. As next steps, the researchers will adjust the band gap, and thus the color. Further, while a high quantum yield from light excitation is promising, device performance under electrical excitation requires separate testing due to additional loss mechanisms. Heo also plans to work toward a phosphorescent version of the molecule, as phosphors are overall more energy-efficient than fluorophores, for use in display technology.Autonomous University of Madrid, University of Valencia, Eberhard Karls University Tübingen and Seoul National University also contributed to this research.&nbsp;

Reaching 98% efficiency in a solid state and 94% in solution, the small fluorescent molecule's design could cut down development time and cost for future applications.

Displays, imaging and sensing: New blue fluorophore breaks efficiency records in both solids and solutions

Among emerging solutions, Direct Retinal Projection (DRP) stands out. Rather than projecting onto a screen, DRP beams images directly onto the retina to unlock ultra-clear visuals with minimal eye strain. Yet the effectiveness of DRP hinges on the performance of the underlying light modulation device. That’s why TDK is now repurposing thin film lithium niobate (TFLN), a material long prized in telecommunications, for next-generation AR smart glasses displays.For decades, lithium niobate has been trusted for high-speed modulation in long-haul infrared optical communication. TDK's breakthrough lies in applying this well-established material to the visible light spectrum and adapting it for DRP imaging. With this world-first innovation, TDK is delivering on promises of higher resolution and significantly lower power consumption.<h2>The TFLN Device Concept</h2>In traditional laser projection systems, color modulation is achieved by dynamically adjusting the injection current to red, green, and blue (RGB) laser diodes. This current-based approach alters the power level of each laser, creating the desired mix of colors. However, this method introduces two fundamental constraints: significant power consumption due to current control to change colors thermal inefficiencies and a practical upper limit in switching speed (i.e., typically around 1 GHz) due to the carrier dynamics in semiconductor laser junctions.TDK’s lithium niobate-based projection module fundamentally rewrites this equation. Instead of modulating color through current, the system fixes the injection current at a low, stable level and applies a voltage across a TFLN electro-optic modulator to dynamically alter the phase of each RGB laser beam. This separation of power delivery (via fixed current) and modulation (via voltage) brings profound improvements in both efficiency and speed.At the center of the system is an Active Photonic Integrated Circuit (Active-PIC) fabricated from sputtered TFLN. These modulators leverage the Pockels effect, which is an intrinsic property of lithium niobate wherein the refractive index changes linearly with an applied electric field. By exploiting this effect, TDK can induce precise phase shifts in the optical waveguides without generating excess heat or requiring large drive currents. The result is color modulation at frequencies up to 10 GHz and more, a number ten times faster than what’s possible with laser diode current modulation.In simple terms, TFLN enables color tuning without altering the energy driving the laser itself. This stability makes it ideal for the DRP method, as laser beams must scan across the retina at high speeds to build up an image. Faster switching means higher effective resolution and smoother rendering, while lower power draw extends battery life in AR smart glasses.<h2>TDK’s Breakthrough in Sputtered TFLN</h2>One of the primary challenges that historically prevented lithium niobate from entering the consumer electronics space was its fabrication method. Traditionally, TFLN devices have been manufactured by bonding thick, bulk-grown crystals onto silicon or other substrates. While this method works well for high-performance optical communication systems, it presents serious drawbacks for mass-market applications. Bulk bonding is inherently low-yield, expensive, and difficult to scale. It also limits device miniaturization due to the thickness and fragility of the bonded crystals.TDK’s breakthrough comes in the form of a proprietary sputtering process that enables the deposition of high-quality, single-crystal-like TFLN directly onto sapphire substrate. Using a precisely tuned sputter deposition technique, TDK forms several hundred nanometer-thick TFLN layers with uniform thickness and crystallinity across large-diameter wafers. This process is compatible with standard semiconductor fabrication workflows and allows wafer-scale integration alongside etching, lithography, and metallization steps.Bonded films require manual alignment and polishing. In contracts, sputtered TFLN can be patterned and processed to drastically reduce cost and manufacturing complexity. Furthermore, TDK’s sputtered films exhibit excellent electro-optic performance, with X-ray diffraction confirming the good crystallinity required for low-loss optical waveguides. This has allowed TDK to fabricate fully functional phase modulators and multiplexers in TFLN for the visible light spectrum: a world-first.<h2>A World-First in Visible Light Modulation</h2>While lithium niobate has long been used in infrared applications, TDK is the first to demonstrate its viability for full-color visible light modulation. This includes independent modulation of red, green, and blue lasers and real-time color mixing through an integrated multiplexer.In lab demonstrations, TDK has successfully shown RGB phase modulation and full-color output using their sputtered-film Active-PIC. Notably, TDK has also proved that the system works within the constraints of wearable AR smart glasses validating the design with direct retinal projection demos. <h2>Three Advantages of TDK’s TFLN</h2><h3>Modulation Speed</h3>In traditional laser-based systems, modulation speed is limited by the physical properties of the laser diode itself. Specifically, the carrier recombination rate within the semiconductor junction caps switching frequencies around 1 GHz. While sufficient for lower-resolution displays, this frequency limit restricts how quickly the laser beam can toggle between red, green, and blue during raster scanning. For DRP applications where individual laser pulses trace an image line by line across the retina, this modulation rate becomes a bottleneck to achieving higher resolution.TDK’s TFLN modulators bypass this limitation by decoupling color control from laser current. Instead, they leverage the Pockels effect to enable optical phase modulation purely through applied voltage at frequencies up to 10 GHz and more. This tenfold increase directly translates into faster pixel transitions and a resultant higher number of color changes per scan line and per frame. Practically, this means TFLN modulators can support 4K and 8K retinal imaging while maintaining frame rates up to 60 fps without flicker.  It also opens the door to future high-frame-rate, high-pixel-density displays such as those required for light-field rendering and retinal microdisplays.<h3>Scalability</h3>The scalability of TDK’s TFLN architecture stems from its use of Active-PIC design. Whereas discrete optical systems require manual assembly of modulators, multiplexers, and beam combiners, the Active-PIC consolidates all light-processing elements onto a single TFLN chip. Each waveguide, multiplexer, and modulator is lithographically defined with submicron precision, enabling complex optical functionality in a compact footprint.Such an approach allows resolution to scale through architectural duplication, not through physical expansion. For example, increasing from 720p to 4K+ is as simple as expanding the number of modulator paths and multiplexing channels on the chip, without enlarging the overall module or increasing system power. The uniformity and reproducibility of the sputtered TFLN process ensure consistent performance across high-density arrays for future displays to be scalble. Because all modulation is done on-chip, TDK’s system also reduces optical alignment complexity and allows for cohesive integration with advanced MEMS mirrors and other beam-steering technologies.<h3>Efficiency</h3>Efficiency in optical systems is largely governed by how light is generated and modulated. Conventional current-driven laser modulation requires constant active power to vary intensity, often resulting in unnecessary thermal load and significant energy loss due to resistive and thermal inefficiencies in the diode junctions. In AR glasses, this translates to shorter battery life, increased heat near the user’s face, and thicker device form factors to accommodate thermal management.TDK’s use of TFLN reverses this paradigm. With the injection current fixed near the diode’s threshold and modulation achieved through external voltage, the optical output remains highly stable while power consumption is minimized. Voltage modulation in TFLN requires much less energy per switch and introduces negligible thermal dissipation, even at GHz speeds. In practical terms, this architecture consumes up to 75% less power than traditional current-modulated systems.This has cascading benefits: battery size can be reduced, wearables stay cooler to the touch, and thermal drift, which can degrade image fidelity, is minimized. Furthermore, low-power operation unlocks more sustainable AR systems that are viable for extended wear.<h2>TFLN Imaging Beyond AR Smart Glasses</h2>Although AR smart glasses is the initial target, the implications of TDK's TFLN extend well beyond. Its high-speed modulation and low-power characteristics make it well-suited for<ul><li>Data Center Optical Interconnects: Lower power and faster IO for photonic computing. Specifically, this is more important for a generative AI data center.</li><li>Quantum Photonics: TFLN's precise phase control and electro-optic properties are suitable for quantum circuits.</li></ul>TDK's work with visible light also unlocks new possibilities for consumer-level Visible Light Communication (VLC) and ultrafast wireless transfer, which have long been limited by cost and complexity.<h2>Scaling and Industry Adoption</h2>As with any material breakthrough, industry adoption depends on cost, scalability, and ecosystem readiness. TDK’s sputtered TFLN approach addresses all three. Combining TFLN modulators with photodetectors, amplifiers, and logic layers could enable fully self-contained one-chip ultracompact optical transceiver to be suitable for optical interconnect for generative AI.<h2>Conclusion</h2>TDK's use of TFLN for visible light modulation is a major moment in the evolution of AR smart glasses display systems. By replacing traditional current-based laser control with high-speed, voltage-driven phase modulation, TDK has enabled higher resolution, lower power consumption, and unprecedented scalability.To learn more, <a href="https://www.tdk.com/en/contact/form/index.html?product_information%255binquiry_classification%255d=ads&amp;product_information%255bproduct_category_1%255d=ads-arvr&amp;product_information%255bproduct_category_2%255d=ads-arvr-001" target="_blank" rel="noopener noreferrer">get in touch with TDK here.</a><a href="https://www.wevolver.com/profile/tdk.corporation"></a>

As augmented smart glasses technology edges closer to mainstream adoption, engineers face challenges around display performance. Namely, many seek to achieve higher resolution without driving up power consumption and device bulk.

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Displays, imaging and sensing: New blue fluorophore breaks efficiency records in both solids and solutions

World-First Adoption of Thin Film Lithium Niobate (TFLN) as Imaging Device

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