In the rapidly evolving field of flat optics, metalenses—ultra-thin optical components composed of nanostructures—are reshaping possibilities in imaging, sensing, and photonic integration. Yet, bridging the gap between laboratory breakthroughs and high-volume commercial applications remains a multidimensional challenge, involving advancements in materials, nanofabrication, system integration, and scalable manufacturing.
In this edition of APE Photonics Spotlight, we speak with Dr. Wang Qian, Principal Scientist at A*STAR’s Institute of Materials Research and Engineering (IMRE) and a recognised leader in nanoimaging and metasurface technology. With over 50 publications in top-tier journals such as Science and Nature Photonics and named among the world’s top 2% scientists in 2025, Dr. Wang brings deep expertise in visible-light metalenses, reconfigurable metasurfaces, and their translation into real-world systems.
In the following interview, Dr. Wang discusses recent revolutions in design and materials, critical fabrication hurdles, and the integration of metasurfaces with semiconductor platforms. She also highlights the strategic role of initiatives like Singapore’s National Semiconductor Translation and Innovation Centre (NSTIC) in accelerating the journey from research to commercialization, and shares her outlook on emerging applications and the unique value of platforms such as the Asia Photonics Expo in bridging research and industry.
Q: What are the main process challenges in scaling up metalens production, particularly in fabricating high-aspect-ratio nanopillars and achieving sub-wavelength precision? What recent breakthroughs have enabled the use of mature semiconductor processes for more scalable manufacturing?
A: A metalens wafer is typically fabricated on an optically transparent glass or quartz substrate to support operation in the visible and near-infrared spectral ranges. Unlike conventional CMOS silicon processes, which continue to push electronic feature sizes toward the nanometer regime, metalens fabrication involves comparatively larger features (on the order of tens of nanometers) but demands extremely high aspect ratios, often exceeding 5–10, along with non-periodic, spatially varying patterns. Consequently, advanced semiconductor deep-UV immersion photolithography is increasingly employed for metalens wafer production. Meeting the stringent requirements for nanofabrication resolution, profile fidelity, and across-wafer uniformity pushes both lithography and dry-etching technologies to their operational limits.
A typical 5-mm-diameter metalens comprises hundreds of millions of non-periodic nanostructures, presenting a significant challenge for in-line, nondestructive wafer-scale inspection. To address this, our laboratory has developed a transmission-mode optical inspection system capable of evaluating every metalens across a full wafer. The platform provides rapid, quantitative measurements of key optical performance metrics, delivering immediate feedback to the fabrication team and accelerating process optimisation. Through precise process and recipe control, multi-layer or stacked metalenses have been successfully fabricated.
Overall, overcoming these challenges requires the integration of advanced lithography, etching, and deposition processes, together with rigorous in-line monitoring and optimisation, to achieve high-yield, wafer-scale production of metalenses suitable for commercial deployment.
Q: What revolutionary design approaches and novel material platforms have emerged in recent research on visible-light achromatic metalenses? How impactful are these technological breakthroughs for advancing the commercialization of metalenses in high-end imaging applications, such as mobile photography and precision medical devices?
A: Broadband achromatic metalenses with high focusing efficiency remain a substantial technical challenge, particularly within the visible spectral region, where dispersion requirements are stringent and fabrication constraints impose additional limitations. Recent advances in inverse design, augmented by deep learning-enabled optimisation, have begun to address these limitations by enabling the exploration of design spaces far beyond what is accessible through traditional, hand-tuned meta-atom libraries. These data-driven approaches have yielded free-form nanostructure geometries capable of achieving broadband achromatic performance and wide field-of-view operation that were previously unattainable with conventional parameter sweeps. Notably, multi-layer and stacked metalens configurations designed through such computational frameworks allow independent control of phase and group delay, thereby facilitating broadband achromatic focusing across large portions of the visible spectrum. These developments mark a significant advancement toward realising practical, high-performance metalenses for demanding visible-light imaging applications.
On the materials side, high-index, low-loss dielectrics such as TiO2, SiN, GaN have emerged as leading platforms, owing to their excellent refractive-index contrast, minimal absorption in the visible spectrum, and compatibility with high-volume semiconductor fabrication processes. In addition, wide-bandgap materials and novel platforms like polymer inorganic hybrids, nano-imprinted high-refractive-index resin, and CMOS-compatible ALD dielectrics are expanding the toolkit for scalable, wafer-level manufacturing.
Together, these advances in design methodologies and material innovations are driving visible-light metalenses beyond laboratory demonstrations and towards practical, broadband optical components capable of addressing real-world imaging and sensing applications. Nevertheless, their performance still falls short of traditional multi-element refractive lenses. While fully replacing high-quality lens assemblies in mobile imaging remains challenging, metalenses can be hybrid-integrated into optical systems to significantly reduce the size and weight of optical modules while preserving high imaging performance. These benefits make metalenses particularly appealing for single-wavelength platform applications. At the same time, industry adoption is moving toward multi-metalens architectures that independently address the red, green, and blue bands of the visible spectrum, which are subsequently merged into a reconstructed RGB image, with further quality enhancement enabled through AI-based post-processing.
Dr. Wang Qian, Principal Scientist at A*STAR’s Institute of Materials Research and Engineering (IMRE)
Q: The global market for metasurface-based solutions is projected to grow significantly, with applications expanding beyond communications into sensing, medical imaging, and industrial uses. In your view, which specific application or industry vertical offers the most immediate and viable path for the widespread commercialization of metalens technology? What unique advantages does a flat lens provide in that domain compared to traditional optics?
A: Metasurfaces have already entered early stages of commercialisation, particularly in optical systems where compactness and reduced weight are essential. Their ultra-thin and lightweight form factor eliminates the need for bulky curved elements. In addition, their ability to engineer phase, amplitude, and polarisation at subwavelength resolution enables sophisticated wavefront manipulation within a single layer that would normally require multiple refractive components.
Furthermore, metalenses can be fabricated at the wafer scale using deep-UV lithography or nanoimprint techniques, enabling seamless integration with CMOS-compatible platforms. This includes the possibility of direct fabrication on image sensors or photonic chips, significantly simplifying system architecture and improving alignment accuracy.
Single wavelength light shaping for sensing remains one of the most mature and application-ready functions of metasurfaces. A prominent example is the compact Face-ID module for consumer electronics commercialised by Metalenz, which has now reached mass production. Similarly, Singapore-based startup, Meta Optics, has successfully bought RGB metalenses monolithically integrated with CCD image sensors to market, further demonstrating the viability of metasurface optics in practical imaging applications. Furthermore, Near-IR and mid-IR applications are especially promising for metalenses, as fabrication is comparatively less challenging in these spectral regions. Larger feature sizes reduce process complexity while still enabling high-performance optical functionality.
Q: What are the fundamental materials and engineering challenges in integrating metalenses at the chip level with electronic image sensors? How critical are factors such as packaging, alignment, and thermal management, and what direction do you see the industry taking regarding standardization efforts?
A: CMOS-compatible dielectric materials (TiO₂, SiN, GaN, a-Si) are commonly used in metalens design, making them attractive for direct sensor integration. In practice, however, moving from lab demos to reliable, high-yield modules presents several interlinked materials and engineering challenges.
From an engineering standpoint, wafer-level bonding of a metalens wafer to a sensor wafer is a natural pathway toward large-scale integration. Although metalenses offer relaxed alignment tolerances at the micrometer level, the bonding process remains highly demanding. In particular, dielectric-to-dielectric wafer bonding requires sub-nanometer surface roughness and excellent wafer planarity to achieve a void-free, high-strength interface. These stringent requirements present substantial challenges in surface preparation, bonding quality, and overall packaging reliability. Alternatively, directly fabricating metalenses on the CMOS sensor wafer eliminates alignment issues and is being actively explored by the community. In my view, this approach could become the most promising solution once flat-optics designs are capable of fully replacing the existing optical stack on top of the sensor, including the microlens array and color filters.
After packaging, the metalens structures with their high-aspect-ratio pillars are susceptible to scratching or mechanical damage. Moreover, any material that fills or coats the nanostructures can alter the optical performance. To address this, low-index dielectric materials are being explored to serve as protective layers while preserving the intended functionality of the metalens.
Q: In implementing reconfigurable optical metasurfaces, which control mechanisms — thermal, electrical, or optical actuation — currently show the greatest application potential? How well do these mechanisms meet the demands for response speed, power consumption, and integration density in practical applications such as dynamic imaging, LiDAR, or AR/VR?
A: Among the various control mechanisms for reconfigurable optical metasurfaces, thermal, electrical, and optical actuation each present distinct strengths and limitations, with their suitability determined by key performance requirements such as response speed, power consumption, and integration density. Thermal actuation using phase-change materials provides large, non-volatile tuning ranges but is limited by slower response and higher power consumptions, restricting its use to applications where speed is less critical. Optical actuation offers ultrafast switching but typically requires high-intensity pump beams and complex setups, constraining system-level integration. In my view, electrical actuation currently holds the greatest potential for practical deployment. Electro-optic modulation, carrier-injection tuning, and MEMS-based actuation can achieve nanosecond-to-microsecond switching speeds while consuming lower power than thermal approaches. These capabilities make electrical control particularly compelling for holography dynamic display, AR/VR and LiDAR systems, where real-time wavefront manipulation and compact, high-density integration are essential. At IMRE, for example, a 1-µm-pixel liquid crystal on silicon (LCOS) meta-display has been developed using electrically driven liquid-crystal tuning of metasurfaces to enable high-speed dynamic display functionality.
Q: As a Principal Scientist at IMRE of A*STAR, could you share the institute’s specific strategies in metasurface technology R&D and its industrial translation? In particular, how does IMRE leverage its strengths in materials innovation, process optimization, and industry–academia collaboration to advance this cutting-edge technology?
A: I currently hold a joint appointment with the National Semiconductor Translation and Innovation Centre (NSTIC), (Advanced Photonics) a $180 million national initiative supported by the National Research Foundation (NRF). NSTIC (Advanced Photonics) serves as Singapore’s strategic platform for semiconductor innovation, with a strong focus on advancing flat optics, and photonics technologies.
Our core strength lies in our world-class research team, whose deep expertise continues to attract leading talent in nanophotonics and semiconductor photonics. Across A*STAR particularly Institute of Materials Research and Engineering (IMRE), Institute of Microelectronics (IME), Institute of High Performance Computing (IHPC), Singapore Institute of Manufacturing Technology (SIMTech), and Skin Research Labs (ASRL), we leverage complementary capabilities to accelerate the translation of breakthrough metasurface technologies into industrial impact. At IMRE, we have established strong foundations in materials innovation and metalens solution design. Beyond traditional TiO₂, SiN, and a-Si platforms, we are developing new high-index, low-loss materials specifically tailored for visible-light metalens applications.
Process optimisation and scalable fabrication are also central to our strategy. Through NSTIC (Advanced Photonics), we have access to state-of-the-art, industry-grade facilities, including a 300 mm wafer-scale cleanroom which enables faster iteration cycles, higher throughput, and significantly reduced production costs. This plays a critical role in bridging the gap between research-scale demonstrations and commercially viable manufacturing.
We work closely with industrial partners to co-develop metalens solutions that reduce device size, enhance performance, and enable new functionalities in optical modules and photonic systems. These collaborations ensure that our research is aligned with real-world needs and accelerates the adoption of metasurface technologies in next-generation imaging and sensing applications.
Q: What are your thoughts/expectations for Asia Photonics Expo 2026?
A: APE is Asia’s leading platform for photonics innovation. As researchers, we hope to showcase our latest technologies and demonstrate our capabilities in advanced nanophotonics. Often, industry partners or end-users may not fully understand the potential of emerging technologies, while researchers may lack complete visibility into the detailed problem statements and practical constraints of industry. I expect APE 2026 to serve as a bridge between the two, creating opportunities to educate, connect, and align both sides, and ultimately to drive successful technology translation and commercialisation.
Dr. Wang Qian’s Biography
Dr. WANG Qian obtained her Ph.D. degree from Nanyang Technological University in 2012. She was subsequently awarded the ASTAR International Fellowship and conducted postdoctoral research at the Optoelectronics Research Centre, University of Southampton. Dr. Wang later joined the Institute of Materials Research and Engineering (IMRE), ASTAR, where she is currently a Principal Scientist leading a group dedicated to developing nanoimaging and defect inspection technologies. She also holds a joint position at the National Semiconductor Translation and Innovation Center, focusing on the development of flat lens inspection systems.
Dr. Wang has published over 50 papers in high-impact journals, including Science, Nature Photonics, Light: Science & Applications, and Advanced Materials. Her research interests include metasurface, non-volatile phase-change materials, near-field manipulation of plasmonic and phonon polariton modes, as well as all-optical neuromorphic computing. She has been recognized among the world’s top 2% scientists in the 2025 list compiled by Stanford University and published by Elsevier.
