Conclusion and outlook
Infrared dual-comb polarimetry was introduced as a new polarimetric technique for studies of anisotropic samples in the mid-IR spectral range. IR-DCP enables mid-IR polarimetric measurements of amplitudes and absolute phases at high spectral resolution (1.4 cm–1). The method was applied to characterize a nanofiber scaffold with strong in‑plane anisotropy. Azimuthal images of parallel- and cross-polarized dual-comb spectra were proven to be applicable for direct inspection of anisotropic vibrational properties. Having with a single polarizer configuration access to both amplitudes and absolute phases offers new imaging prospects for cross-polarized sample properties.
Furthermore, IR-DCP provides sub-millisecond measurement times of 275 µs or less (potentially even sub-µs). The accessible integration times are far below those achievable with conventional FTIR techniques, thus enabling future applications regarding sub-ms resolved spectral investigations of irreversible or non-cyclic variations of structural sample properties. The superior time resolution of IR-DCP compared with other IR approaches renders the method potentially interesting for many applications in photonics such as process control in the fabrication of waveguides and functional metasurfaces. In general, the novel time-resolved polarimetric possibilities could have a high potential scientific impact for previously unfeasible in situ andoperando studies of irreversible or noncyclic processes or sample modifications. Further future applications of IR‑DCP will also become available in other polarimetric measurement geometries.
In summary the developed IR dual-comb polarimetric method has high potential for chemical and structural studies, e. g., of anisotropic samples, protein dynamics, phase transitions, chemical modifications and reactions, which is relevant for material science, catalysis, biophysics, photonics, rheology and metrology.
Notes The authors declare no conflicts of interest.
Data availability statement The data that support the findings of this study are available from the corresponding author upon reasonable request.