The solar-blind ultraviolet band (200–280 nm) is one of the most information-rich yet under-exploited regions of the spectrum. Stratospheric ozone removes almost all natural solar background in this range, so a UV-C photon detected near the ground is usually a meaningful signal: a corona discharge, flame, muzzle flash, missile plume, or deliberate ultraviolet communication link. This unusually low-background environment makes solar-blind sensing a strategic capability and one of the two spectral pillars of our Center’s photocathode and sensor roadmap. Current research is led by wide- and ultrawide-bandgap semiconductor platforms. AlGaN photodetectors use a tunable bandgap to provide intrinsic solar blindness without external filters, and AlGaN focal-plane arrays have demonstrated solar-blind imaging [1].
AlGaN/AlN/GaN heterojunction nanowire detectors have also been studied for underwater optical communication, combining improved responsivity and response speed [2]. Ga₂O₃ is a complementary ultrawide-bandgap platform for solar-blind detection [3]. Recent examples include a self-powered α-Ga₂O₃/Ta photoelectrochemical detector [4] and a heterojunction device that discriminates between ultraviolet wavelength bands using differences in current relaxation [5]. These solid-state approaches complement vacuum-based photocathode and microchannel-plate detection architectures.
At the Photonics International R&D Center, our UV-C programme concentrates on the complete intensified detection chain. Our work includes mapping solar-blind photocathode response across 200–280 nm, characterising microchannel-plate gain under UV-generated photoelectron statistics, measuring out-of-band rejection the decisive figure of merit for genuine solar blindness and performing calibrated radiometry at the extremely low photon fluxes typical of operational UV-C signatures. Vacuum-intensified and solid-state AlGaN detection paths are evaluated on the same test benches, providing European partners with a consistent evidence base for architecture selection in laser-warning, corona-inspection, flame-detection, and threat-detection systems.
The remaining challenges are both material and system-level. They include reliable p-type doping of high-aluminium AlGaN, UV-transparent optics and durable coatings, detector ageing under ultraviolet exposure, and the absence of standardised performance benchmarks for UV-C imagers. Looking ahead, we expect dual-band sensor suites in which a solar-blind UV-C channel provides low-false-alarm event detection while an intensified visible/near-infrared channel supplies imaging context, with the two streams fused computationally. Our validation infrastructure is being specified so that these dual-band prototypes can be characterised end-to-end within a single laboratory, from calibrated illumination and spectral rejection to final image quality and detection probability.
ATSAUCES
[1] Cai, Q., You, H., Guo, H., Wang, J., Liu, B., Xie, Z., Chen, D., Lu, H., Zheng, Y., & Zhang, R. (2021). Progress on AlGaN-based solar-blind ultraviolet photodetectors and focal plane arrays. Light: Science & Applications, 10, Article 94. https://doi.org/10.1038/s41377-021-00527-4
[2] Xue, J., Wang, S., Tong, J., Yang, G., Parkhomenko, I., Komarov, F., Liu, Y., Cai, Q., Wang, J., & Zhi, T. (2024). Achieving a high-responsivity and fast-response-speed solar-blind photodetector for underwater optical communication via AlGaN/AlN/GaN heterojunction nanowires. ACS Applied Electronic Materials, 6(6), 4643–4652. https://doi.org/10.1021/acsaelm.4c00636
[3] Wang, L., Xu, S., Yang, J., Huang, H., Huo, Z., & Li, J. (2024). Recent progress in solar-blind photodetectors based on ultrawide bandgap semiconductors. ACS Omega, 9(24), 25429–25447. https://doi.org/10.1021/acsomega.4c02897
[4] Liu, Y., Gao, Q., Wang, X., & Gao, C. (2026). Construction of α-Ga₂O₃/Ta photoanode for self-powered photoelectrochemical solar-blind ultraviolet photodetector. Applied Physics A, 132, Article 163. https://doi.org/10.1007/s00339-026-09364-x
[5] Wang, Y., Fu, R., Han, Y., Li, B., Shen, A., & Liu, Y. (2026). Solar-blind enhanced dual-band ultraviolet photodetector. Small, 22(25), Article e14917. https://doi.org/10.1002/smll.202514917