12 Jan. Exceptionally angular-stable optical filters
Novel optical filters that may finally overcome the long-standing issue of angular sensitivity could pave the way for innovations in photonics, sensing, optical imaging, and displays. Until now, the performance of optical filters has degraded considerably for light at non-normal angles of incidence. This performance decline can significantly compromise the accuracy of optical sensors, such as in high-precision measurements.
Filters based on quantum effect
Researchers from the University of Cologne, Hasselt University, and the University of St Andrews report on the successful use of strong coupling between photons and the energy states of an organic material. This process gives rise to so-called polaritons. “Ideally, one would like to avoid any kind of absorption in spectral filters so as not to compromise their optical quality,” explains Dr. Andreas Mischok from the University of Cologne. “However, we specifically make use of light absorption of organic materials to generate angle-stable polariton modes with excellent transmission properties.”
Spectrally stable
The team fabricated filters with unique angular stability. According to their report, these filters show a spectral shift of less than 15 nm even at viewing angles over 80°. Additionally, complex multilayer designs led to transmission of up to 98%, comparable to the best conventional filters currently available. Also, polariton filters integrated into organic photodiodes produced narrow-band photodetectors that potentially advancing hyperspectral imaging – such as material characterization – and compact optical sensing.
Novel filter principle unlocks multiple applications
According to the researchers, the technology could be extended to polymers, perovskites, quantum dots, and other materials, expanding the new filter principle to a wider wavelength range. Possible applications for polariton filters include microoptics, displays, sensor technologies, and biophotonics. The researchers believe that the angle independence of the new filters could simplify optical system design and expand functionality across all these areas.
Original publication
[Mischok, A., Siegmund, B., Le Roux, F. et al., Breaking the Angular Dispersion Limit in Thin-Film Optics by Ultra-Strong Light-Matter
Coupling. Nat Commun 15, 10529 (2024). DOI: 10.1038/s41467-024-54623-1]
Source: www.uni-koeln.de
Image: Springer Nature, aus Nat Commun 15, 10529 (2024)