Over the past few decades, significant attention has been paid to the biomedical applications of terahertz (THz) technology. Nowadays, THz spectroscopy and imaging have allowed numerous demanding problems in the biological, medical, food, plant and pharmaceutical sciences to be solved. Among the biomedical applications, the label-free diagnosis of malignant and benign neoplasms represents one of the most attractive branches of THz technology. Despite this attractiveness, THz diagnosis methods are still far from being ready for use in medical practice. In this review, we consider modern research results in the THz diagnosis of malignant and benign neoplasms, along with the topical research and engineering problems which restrain the translation of THz technology to clinics. We start by analyzing the common models of THz-wave-tissue interactions and the effects of tissue exposure to THz waves. Then, we discuss the existing modalities of THz spectroscopic and imaging systems, which have either already been applied in medical imaging, or hold strong potential. We summarize the earlier-reported and original results of the THz measurements of neoplasms with different nosology and localization. We pay attention to the origin of contrast between healthy and pathological tissues in the THz spectra and images, and discuss the prospects of THz technology in

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.

In this letter, we reported the experimental observation of a photonic hook (PH)—a type of near-field curved light generated at the output of a dielectric cuboid, featuring a broken symmetry and dimensions comparable to the electromagnetic (EM) wavelength. Given that the specific value of the wavelength is not critical once the mesoscale conditions for the particle are met, we verified these predictions experimentally using a 0.25 THz continuous-wave source. The radius of curvature associated with the PH-generated is smaller than the wavelength, while its minimum beam-waist is about 0.44λ. This represents the smallest radius of curvature ever recorded for any EM beam. The observed phenomenon is of potential interest in optics and photonics, particularly, in super-resolution microscopy, manipulation of particles and liquids, photolithography, and material processing. Finally, it has a universal character and should be inherent to acoustic and surface waves, electrons, neutrons, protons, and other beams interacting with asymmetric mesoscale obstacles.