Репозиторий Университета

© 2018 IEEE. We have proposed an approach to improve the resolution of terahertz (THz) imaging using the effect of solid immersion - i.e. a reduction in the dimensions of the electromagnetic beam caustic by its formation in a free space, behind the medium possessing high refractive index. We have designed a THz solid immersion lens (SIL) comprised of a polymer wide-aperture aspherical singlet and a crystalline truncated sphere mounted in front of the image plane. We have proposed an approach for the object handling at the focal plane of the THz SIL. We have combined numerical simulations and experimental studies to demonstrate the advanced 0.2λ spatial resolution of the proposed THz SIL - it is beyond the 0.5λ Abbe limit. Finally, we have assembled the continuous-wave THz SIL imaging system and applied it for studying various objects with sub-wavelength variations of structure and dielectric properties.

© 2018 IEEE. Modern laser technologies have a wide range of scientific, commercial, medical and other applications. In medicine, lasers are used both for diagnostic, therapeutic, and surgical purposes. Safety of laser radiation in assisted reproductive technologies is discussed in the paper. Efficiency of using femtosecond (fs) laser pulses to perform noncontact embryo biopsy as well as laser-assisted hatching is shown. First results on femtosecond laser marking on the surface of embryo outer shell for individual embryo tagging are also presented. Question of safety of THz radiation for living objects (starting at the cellular level and ending with the organism in whole) is still a matter of controversy and requires further study. Experimental study of high-power THz pulses effect on living 2D cell culture is presented. MSC cells are exposed to multiple (from 80 to 100) THz pulses with intensities up to 1 MV/cm. No short-term damage effects are observed during first hours post cell irradiation.

© 2018 IEEE. We have proposed a method of THz solid immersion microscopy, which yields imaging soft biological tissues with the sub-wavelength resolution up to 0.2-wavelengths. To achieve this advanced resolution, it employs a solid immersion phenomenon - i.e. a reduction in the dimensions of the THz beam caustic by its formation on a small distance behind the medium featuring high refractive index. We have assembled an experimental setup, which realizes the principles of the THz solid immersion microscopy, and proposed an approach for handling the soft tissue at the object plane. This setup uses a backward-wave oscillator, as a source of continuous-wave THz radiation, and a Golay cell, as a detector of the THz field intensity. We have examined the resolution of the THz solid immersion microscopy using both numerical simulations and experimental studies. Finally, in order to highlight the prospective of the proposed THz imaging modality, we have applied the experimental setup for imaging of representative examples of biological tissues.

© 2018 SPIE. Application of terahertz (THz) spectroscopy for biological tissues is strongly limited by the extremely low penetration depth due to THz absorption by tissue water. One of the possible solution of such problem is the usage of THz wave penetration-enhancing agents (PEA) for optical clearing of tissues. In the present paper, the transmission-mode THz spectroscopy of a set of PEAs (polyethylene glycol with different molecular weight, propylene glycol, ethylene glycol, and dimethyl sulfoxide) was performed in order to reconstruct their dielectric properties and compare them with that of water. The obtained results emphasize the feasibility of using PEG to enhance the depth of THz wave penetration into tissues.

© COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only. We have performed the in vitro terahertz (THz) spectroscopy of human brain tumors. In order to fix tissues for the THz measurements, we have applied the gelatin embedding. It allows for preserving tissues from hydration/dehydration and sustaining their THz response similar to that of the freshly-excised tissues for a long time after resection. We have assembled an experimental setup for the reflection-mode measurements of human brain tissues based on the THz pulsed spectrometer. We have used this setup to study in vitro the refractive index and the amplitude absorption coefficient of 2 samples of malignant glioma (grade IV), 1 sample of meningioma (grade I), and samples of intact tissues. We have observed significant differences between the THz responses of normal and pathological tissues of the brain. The results of this paper highlight the potential of the THz technology in the intraoperative neurodiagnosis of tumors relying on the endogenous labels of tumorous tissues.