The last SPIE Optics + Optoelectronics conference took place from the 7th to the 10th of April 2025 in Prague, Czech Republic. Organised by the International Society for Optics and Photonics (SPIE), it gathered researchers, engineers and industry professionals in the field.
The LEARN project’s coordinator, the International Iberian Nanotechnology Laboratory (INL), presented some LEARN project research for the development of novel sensors to better detect volatile organic compounds (VOCs) in the air.
Enhancing Third-Harmonic Generation (THG) in the UV-A spectrum using TiO₂/SiO₂ metasurfaces
Diogo Poeta, a researcher from INL’s Diéguez Group, exhibited the poster ‘TiO2/SiO2 metasurfaces for the enhancement of THG with pump wavelengths in the UV-A’. The research compares different oxidising agents used in atomic layer deposition (ALD) of TiO₂ thin films, showing that O₃-based films offer superior optical properties (high refractive index, low absorption, and smooth morphology), leading to better nonlinear optical performance. These findings support the development of advanced photonic devices that operate efficiently under UV-A illumination.
This research is part of the LEARN project’s Work Package 4, which focuses on developing innovative sensors to better detect ultrafine particles (UFPs) and volatile organic compounds (VOCs). The optimised TiO₂ metasurfaces described in the poster could be integrated into UV-sensitive optical sensors, enhancing detection capabilities for air pollutants thanks to their compact fabrication and high performance.
VOC photoionisation via tuneable monochromatic VUV
Rafael Vilarinho, a researcher from INL’s Diéguez Group, gave an oral presentation on ‘VOC photoionisation via tuneable monochromatic VUV‘, demonstrating the photoionisation of Volatile Organic Compounds (VOCs) utilising tuneable quasi-monochromatic Vacuum UltraViolet (VUV) light generated by Third-Harmonic Generation (THG) in suspended SiO2 nanomembranes.
The research details efficient THG based on the optimisation of nanomembrane thickness and engineering considerations to integrate an effective collection and detection of pico-ampere-level photoionisation currents.
Finally, it establishes the sensitivity and selectivity of the setup towards the detection of ethanolamine, limonene and eucalyptol. These results mean a first step towards selective real-time air quality monitoring of problematic toxic, high-molecular-weight VOCs such as benzene, toluene, ethylbenzene and xylene isomers, also known as BTEX compounds.
Sources: Poeta, D., Vilarinho, R., Mahmoodnia, H., Calaza, C., Fonseca, H., Miranda, A., & De Beule, P. A. A. (2025). TiO₂/SiO₂ metasurfaces for the enhancement of THG with pump wavelengths in the UV-A [Conference poster]. SPIE 2025. International Iberian Nanotechnology Laboratory & Faculty of Physics, Bielefeld University.
Vilarinho, R., Mahmoodnia, H., & Maibohm, C. (2025, April 7). VOC photoionization via tuneable monochromatic VUV [Conference presentation]. SPIE Optics + Optoelectronics 2025, Prague, Czech Republic. https://spie.org/optics-optoelectronics/presentation/VOC-photoionization-via-tuneable-monochromatic-VUV/PC13524-2
© Images by SPIE 2025, retrieved from spie.org
The LEARN project is a Horizon Europe project meant to monitor and evaluate indoor air quality at schools around Europe and its impact on children’s health. Our main goal is to develop and deploy novel sensors that can detect possibly harmful air pollutants, as well as advanced biosensors and optimised air remediation strategies. Find out more about our EU-funded project!
