Reflection-mode continuous-wave 0.15λ-resolution terahertz solid immersion microscopy of soft biological tissues

Abstract

We have developed a method of terahertz (THz) solid immersion (SI) microscopy for continuous-wave reflection-mode imaging of soft biological tissues with a sub-wavelength spatial resolution. In order to achieve strong reduction in the dimensions of the THz beam caustic, an electromagnetic wave is focused into the evanescent field volume behind a medium with a high refractive index. We have experimentally demonstrated a 0.15λ-resolution of the proposed imaging modality at λ = 500 μm, which is beyond the Abbe diffraction limit and represents a considerable improvement over the previously-reported arrangements of SI imaging setups. The proposed technique does not involve any sub-wavelength near-field probes and diaphragms, thus, avoiding the THz beam attenuation due to such elements. We have applied the developed method for THz imaging of various soft tissues: a plant leaf blade, cell spheroids, and tissues of the breast ex vivo. Our THz images clearly reveal sub-wavelength features in tissues, therefore, promising applications of THz SI microscopy in biology and medicine.

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“…− низкое пространственное разрешение ТГц оптических систем, обусловленное дифракционным пределом и большой длиной волны излучения [20][21][22];…”

Metallic and dielectric metasurfaces in photoconductive terahertz devices: a review

“…To date, the terahertz (THz) frequency range has found wide applications in many fields ranging from condensed matter physics [1][2][3][4] and material science 5,6 to gas sensing [7][8][9] and pharmaceutical industry 10 as well as various security [11][12][13][14][15][16] and biomedical [17][18][19][20][21][22] applications. All of these require high-sensitive and broadband THz instruments, in particular, efficient operation in real time and at room temperature.…”