Hinrichs, K.; Blevins, B.; Furchner, A.; Yadavalli, N.S.; Minko, S.; Horvath, R.; Mangold, M.: Infrared dual-comb polarimetry of anisotropic polymer sheets and fibers. Natural Sciences 3 (2023), p. e20220056/1-8
10.1002/ntls.20220056
Open Access Version
Abstract:
The mid-infrared (mid-IR) anisotropic optical response of a material probes vibrational fingerprints and absorption bands sensitive to order, structure, and direction-dependent stimuli. Such anisotropic properties play a fundamental role in catalysis, optoelectronic, photonic, polymer and biomedical research and applications. Infrared dual-comb polarimetry (IR-DCP) is introduced as a powerful new spectroscopic method for the analysis of complex dielectric functions and anisotropic samples in the mid-IR range. IR-DCP enables novel hyperspectral and time-resolved applications far beyond the technical possibilities of classical Fourier-transform IR approaches. The method unravels structure–spectra relations at high spectral bandwidth up to 90 cm−1 and short integration times of 65 μs, with previously unattainable time resolutions for spectral IR polarimetric measurements for potential studies of noncyclic and irreversible processes. The polarimetric capabilities of IR-DCP are demonstrated by investigating an anisotropic inhomogeneous freestanding nanofiber scaffold for neural tissue applications. Polarization sensitive multi-angle dual-comb transmission amplitude and absolute phase measurements (separately for ss-, pp-, ps-, and sp-polarized light) allow the in-depth probing of the samples’ orientation-dependent vibrational absorption properties. Mid-IR anisotropies can quickly be identified by cross-polarized IR-DCP polarimetry.