Signatures of top versus bottom illuminations and their predicted implications for infrared transmission microspectroscopy.

Autor: Kong B; Faculty of Science and Technology, Norwegian University of Life Sciences, Aas, Norway., Blümel R; Department of Physics, Wesleyan University, Middletown, Connecticut, USA., Ylä-Oijala P; Department of Electronics and Nanoengineering, Aalto University, Espoo, Finland., Wallén H; Department of Electronics and Nanoengineering, Aalto University, Espoo, Finland., Sihvola A; Department of Electronics and Nanoengineering, Aalto University, Espoo, Finland., Kohler A; Faculty of Science and Technology, Norwegian University of Life Sciences, Aas, Norway.
Jazyk: angličtina
Zdroj: Journal of biophotonics [J Biophotonics] 2024 Oct; Vol. 17 (10), pp. e202400079. Date of Electronic Publication: 2024 Aug 11.
DOI: 10.1002/jbio.202400079
Abstrakt: Since both top and bottom illuminations are widely used in infrared transmission measurements, in this paper, we study the effects of different illuminations on the signatures in infrared microspectroscopy. By simulating a series of dielectric samples, we show that their extinction efficiency, Q ext , remains unchanged when the direction of the incident plane wave is reversed, even though the field distributions both inside and outside of the sample may be dramatically different. We find features in Q ext that are correlated with whispering gallery modes for one beam direction and correspond to completely different field distributions for the opposite beam direction. In addition, by linking the optical theorem and the reciprocity relation of far-field scattered field, we rigorously prove the invariance of Q ext for arbitrary dielectric targets under opposite plane-wave illuminations. Furthermore, we show the difference in the apparent absorbance spectrum for opposite beam directions when considering numerical apertures.
(© 2024 The Author(s). Journal of Biophotonics published by Wiley‐VCH GmbH.)
Databáze: MEDLINE
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