In a significant leap forward for infrared imaging technology, researchers at Nanchang University have engineered an innovative silicon metasurface that transforms infrared (IR) light into visible light with unprecedented efficiency. This breakthrough device leverages advanced nanophotonic design to overcome longstanding challenges in IR detection, setting a new benchmark for compact, room-temperature infrared upconversion imaging.
Infrared light, although crucial to numerous applications such as night vision, medical diagnostics, and industrial monitoring, remains largely inaccessible to conventional silicon-based imaging sensors. Traditional infrared detectors rely heavily on complex, costly, and cryogenically cooled semiconductor materials, which limit their deployment in portable or consumer devices. An alternative strategy has been to “upconvert” infrared photons into visible wavelengths, thus enabling the use of standard silicon cameras known for their sensitivity and compactness. Nevertheless, achieving efficient nonlinear optical conversion in miniaturized, chip-scale platforms has proven a formidable challenge—until now.
The research team led by Professor Tingting Liu has developed an ultra-thin silicon chip patterned with a meticulous array of nanoscale silicon disks, forming a so-called metasurface. This metasurface exploits a unique optical resonance phenomenon to trap and intensify incoming infrared light within nanoscale volumes. By amplifying the local electromagnetic field, the device dramatically boosts silicon’s intrinsic third-order nonlinear optical response, enabling effective third-harmonic generation (THG)—a frequency tripling process that converts IR light into bright visible green light.
At the heart of this achievement is the mastery of a sophisticated optical mode known as a quasi-bound state in the continuum (quasi-BIC). Bound states in the continuum are modes that remain confined without radiating energy despite existing within the spectrum of free-space waves. By introducing a delicate spatial asymmetry to the silicon nanodisks, the team transformed a perfectly trapped, non-radiative mode into a leaky, yet high-quality (high-Q) resonance. This quasi-BIC resonance exhibits an impressive quality factor on the order of 4000, indicating exceptionally low energy loss and prolonged photon confinement within the structure.
The enhanced light-matter interaction facilitated by this quasi-BIC resonance leads to a third-harmonic generation efficiency of approximately 3×10^-5—an unprecedented performance for CMOS-compatible silicon metasurfaces. This breakthrough marks a transformative advancement over previous nonlinear silicon devices, which suffered from limited conversion efficiencies and significant fabrication challenges. Importantly, the use of silicon, a widely available and CMOS-friendly material, ensures compatibility with established semiconductor manufacturing processes, paving the way for scalable and cost-effective production of these metasurface chips.
Beyond raw efficiency, the metasurface device demonstrates its true versatility through direct infrared imaging capabilities. Acting as a dense parallel array of nanoscale converters, the chip can faithfully translate intricate IR images projected onto it into corresponding visible images. The research team has showcased high-fidelity upconversion imaging of standard resolution targets, such as the Siemens star pattern, as well as custom 3D-printed test objects. Optical resolution reaches finely detailed imaging at approximately 6 micrometers spatial scale, all achieved with a single continuous-wave IR pump laser under ambient room temperature conditions.
This advance addresses the critical bottleneck that has long impeded the practical adoption of nonlinear metasurface-based upconversion technology: balancing compactness with conversion efficiency and operational simplicity. By circumventing the bulky, alignment-sensitive nonlinear crystals traditionally used, the silicon metasurface platform offers an elegant and integrable solution, ideal for next-generation infrared sensing and imaging. The device’s room-temperature operation negates the need for complex cooling systems, substantially reducing power consumption and system complexity.
The implications of this work extend broadly across sectors reliant on infrared detection and imaging. Security and surveillance systems stand to gain from enhanced night-vision capabilities embedded into compact, robust hardware. Industrial automation and quality control processes can benefit from high-resolution IR imaging with straightforward silicon sensor integration, enabling real-time defect detection and process monitoring. In consumer electronics, the potential for embedding efficient IR cameras into smartphones and wearable devices becomes increasingly tangible.
Scientifically, this study underscores the power of tailoring light confinement and resonance properties at the nanoscale to elevate nonlinear optical phenomena. The strategic employment of quasi-BIC modes to create ultra-high-Q resonances within accessible materials like silicon highlights a promising paradigm for enhancing other nonlinear optical processes, such as frequency conversion, all-optical switching, and quantum photonics. This could stimulate future research into metasurface-enabled photonic devices with multifunctional capabilities embedded within ultra-compact footprints.
Professor Tingting Liu’s interdisciplinary expertise in micro/nano-photonics and signal processing has been instrumental in realizing this milestone. Under her leadership, the team has combined rigorous theoretical modeling with cutting-edge nanofabrication techniques to optimize the metasurface architecture. The result is a scalable and reproducible platform firmly grounded in CMOS technology while circumventing the limitations imposed by traditional infrared detector materials.
As the field of photonics increasingly gravitates towards integrated and miniaturized solutions, this work sets a new standard for how nonlinear optical metasurfaces can be harnessed for practical applications. The synergy between high-quality resonances, material engineering, and nanoscale device fabrication demonstrated here suggests a bright future for compact infrared imaging technologies that are accessible, efficient, and versatile.
In conclusion, the ultra-thin silicon metasurface developed by Nanchang University’s team represents a transformative advance in infrared photonics. By achieving record third-harmonic generation efficiency through high-Q quasi-BIC resonances, the device opens up new avenues for low-cost, high-performance infrared imaging at room temperature. Its compatibility with existing silicon technology and demonstrated imaging capabilities herald a new era in nonlinear optical devices poised to impact diverse areas including defense, healthcare, industry, and consumer electronics. This breakthrough underscores the growing potential of metasurfaces to revolutionize how light manipulation enables next-generation sensing and imaging systems.
Subject of Research: Infrared upconversion imaging using nonlinear silicon metasurfaces empowered by quasi-bound states in the continuum (quasi-BIC).
Article Title: High-efficiency infrared upconversion imaging with nonlinear silicon metasurfaces empowered by quasi-bound states in the continuum.
News Publication Date: Not explicitly stated; article DOI suggests 2026.
Web References:
– DOI: http://dx.doi.org/10.29026/oea.2026.250257
Image Credits: OEA (Opto-Electronic Advances)
