THz birefringence of different tissue types probed by polarization‐sensitive THz solid immersion microscopy

Abstract

Terahertz (THz) technology has diverse applications in label-free medical diagnosis and therapy [1–3]. However, many of them rely on effective medium theory, describing interaction of THz waves with tissues. This theory considers tissues as spatially homogeneous and optically isotropic media at the scales of THz waves. Recent research, however, has discovered mesoscale (∼λ) heterogeneities in tissues, where λ represents the wavelength. In this work we study one of the aspects of this phenomenon, namely effects of the THz‐wave anisotropy in certain tissue types. We used polarization-sensitive reflection-mode THz solid immersion (SI) microscope [4–7]. This microscope, based on a silicon hemispherical SI lens, metal-wire-grid polarizer and analyzer, a 0.6 THz backward-wave oscillator (BWO), and a Golay detector, enables the study of local polarization-dependent responses of mesoscale tissue elements with a high resolution up to 0.15λ. Our microscope was employed to investigate the THz birefringence (structural optical anisotropy) of freshly-excised muscle, tendon, brain and vessel rat tissues. We analyzed the distribution of the refractive index of THz waves in these tissue samples and found significant optical birefringence associated with their directional ordered structure. The results highlight the potential of polarization-sensitive THz microscopy in biophotonics and medical imaging.
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[7] Chernomyrdin N. V, Il'enkova D.R., Zhelnov V.A., Alekseeva A.I., Gavdush A.A., Musina G.R., Nikitin P. V, Kucheryavenko A.S., Dolganova I.N., Spektor I.E., Tuchin V. V, and Zaytsev K.I., "Quantitative polarization-sensitive super-resolution solid immersion microscopy reveals biological tissues’ birefringence in the terahertz range," Scientific Reports 13, 16596 (2023) , DOI:10.1038/s41598-023-43857-6.

Speaker

Darya Il’enkova
Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow, Russia;
Russia

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