Researchers at North Carolina State University have made a significant breakthrough in the field of infrared optics by enhancing the use of thin films to compress and propagate infrared light. Their latest work demonstrates remarkable improvements in the distance this squeezed light can travel, the range of infrared wavelengths it can manipulate, and the ability to integrate these thin films onto diverse substrates. These findings could revolutionize the practical application of infrared technologies in various fields, including thermal management, photonics, and molecular sensing.
At the heart of this research lies a crystalline membrane composed of strontium titanate (SrTiO3). Previous studies by the team revealed that this material, when deposited on silicon substrates, had intriguing light-confining properties but suffered from excessive energy losses. These losses, primarily converted into heat, limited the distance that infrared light could effectively propagate, thus constraining practical uses. The new research addresses this limitation by isolating the strontium titanate membrane from direct contact with silicon, which was suspected to be the main source of the energy loss.
To probe the intrinsic characteristics of the suspended strontium titanate films, the researchers conducted detailed experiments at the Advanced Light Source facility operated by Lawrence Berkeley National Laboratory. By removing the substrate influence, they discovered that the membrane exhibited drastically reduced loss, allowing infrared light to travel four times farther than previously recorded. This low-loss attribute aligns the strontium titanate membrane’s performance with some of the most efficient polaritonic materials available today, offering promising potential for real-world applications.
The technical underpinning here involves a complex interplay between phonons, photons, and polaritons. Phonons are quantized vibrations of atoms within a material, essentially manifestations of sound or mechanical energy dissipation. Photons, on the other hand, are fundamental units of electromagnetic radiation — what we literally perceive as light. When an infrared photon couples with an optical phonon, a special quasiparticle called a phonon polariton emerges. These polaritons enable the confinement and guidance of light waves along surfaces or interfaces in ways that bulk materials cannot achieve. The strontium titanate membranes excel precisely due to their ability to sustain these surface phonon polaritons with minimal energy loss.
Another profound discovery from suspending the strontium titanate membrane was its capability to confine far-infrared light in addition to mid-infrared light. Earlier experiments restricted these films to squeezing only mid-infrared wavelengths, but the new results provide compelling experimental validation that far-infrared confinement is attainable. This expansion of operational wavelengths opens doors to novel applications, including advanced thermal management technologies where heat conversion into infrared radiation is crucial. It also enhances the sensitivity and versatility of molecular sensing devices, which rely on specific infrared wavelengths to detect chemical signatures.
The researchers emphasize the versatility of these thin films by successfully demonstrating their integration onto substrates of various geometries and materials. They suspended these membranes over void spaces and tested them on non-silicon substrates aimed at preserving the crucial low-loss properties. This adaptability distinguishes the strontium titanate films from many other polaritonic materials that often require rigid, planar, or exotic substrates, thus severely limiting their manufacturability and scalability.
Scaling production remains a pervasive challenge in nanophotonics, but this research offers optimistic prospects. The fabrication method used to create these SrTiO3 nanomembranes is more scalable compared to other techniques used for polaritonic materials. This development is vital if these membranes are to transition from the laboratory environment into commercial technologies where cost-effectiveness and reproducibility are key factors.
With these advances, the team anticipates applications ranging from next-generation infrared imaging systems to environmental sensors capable of detecting minute chemical changes. The expanded wavelength control and efficient propagation promise enhanced resolution and sensitivity, potentially transforming sectors such as healthcare diagnostics, security scanning, and chemical hazard detection.
The foundational understanding achieved also sheds light on the fundamental physics of light-matter interaction at the nanoscale. By isolating and characterizing the intrinsic properties of suspended membranes, researchers have paved the way for refined models that can predict and optimize polaritonic behavior in various materials. This deeper grasp is critical as the field moves toward complex integrated photonic circuits necessary for quantum computing and ultrafast communication networks.
Collaboration between NC State, Lawrence Berkeley National Laboratory, and the University of Geneva brought together expertise in materials science, spectroscopy, and theoretical modeling to accomplish these milestones. This multidisciplinary approach highlights the importance of combining experimental and theoretical efforts to tackle the challenges inherent in nano-optics and photonic device engineering.
The research was supported generously by agencies including the U.S. National Science Foundation, the American Chemical Society Petroleum Research Fund, and the Swiss National Science Foundation. Their commitment underscores the scientific and technological significance of developing materials that can control infrared light with greater efficiency and flexibility.
Looking forward, the team is eager to partner with industry players interested in harnessing these thin films for scalable, practical devices. The marriage of low-loss phonon polariton propagation, expansive wavelength range, and flexible integration presents an exciting frontier for innovation that could impact optical communication, thermal imaging, and beyond.
This pioneering work was detailed in the open-access paper titled “Low-Loss Far-Infrared Surface Phonon Polaritons in Suspended SrTiO3 Nanomembranes,” published in the journal Advanced Functional Materials. The paper’s lead author, Konnor Koons, alongside co-authors from NC State and international collaborators, provides comprehensive experimental data and theoretical insight validating the extraordinary potential of these suspended membranes for advancing infrared nanophotonics.
Subject of Research: Not applicable
Article Title: Low-Loss Far-Infrared Surface Phonon Polaritons in Suspended SrTiO3 Nanomembranes
News Publication Date: 12-May-2025
Web References:
https://news.ncsu.edu/2024/06/squeezing-infrared-light/
http://dx.doi.org/10.1002/adfm.202501041
References:
Koons, K., Ghanbari, R., Wang, Y., Bechtel, H., Gilbert Corder, S., Taboada-Gutiérrez, J., & Kuzmenko, A. (2025). Low-Loss Far-Infrared Surface Phonon Polaritons in Suspended SrTiO3 Nanomembranes. Advanced Functional Materials. https://doi.org/10.1002/adfm.202501041
Image Credits: Not specified
Keywords
Infrared light, thin films, strontium titanate, phonon polaritons, far-infrared confinement, mid-infrared, nanomembranes, low-loss propagation, photonics, thermal management, molecular sensing, Advanced Light Source
