Abstract-Opal-based terahertz optical elements fabricated by self-assembly of porous SiO2 nanoparticles

V. E. Ulitko, G. M. Katyba, V. A. Zhelnov, I. M. Shmytko, G. A. Emelchenko, I. E. Spector, V. M. Masalov, V. N. Kurlov, K. I. Zaytsev, M. Skorobogatiy, 

 Fabrication of the cylindrical convex-plane lenses by mechanical processing of bulk pieces of nanoporous SiO2${}_2$. (a) Multirun grinding of the lenses using rotational holder, and Removal of lenses from the holder after grinding. (b) 3D schematic of a cylindrical lens. (c) Photo of the fabricated lenses made of two nanoporous SiO2${}_2$ materials, annealed at the temperatures of 900$900$ and 1200∘${1200}^{\circ }$C and, thus, featuring different refractive indices and focal distances. (d) SEM images of the two nanoporous SiO2${}_2$ pieces made of 300$300$-nm-diameter nanoparticles and annealed at the temperatures of 900$900$ and 1200∘${1200}^{\circ }$C, respectively.

https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-29-9-13764&id=450313

In this paper, we study artificial opals as a promising material platform for terahertz (THz) optics. Materials were synthesized using self-assembly of porous SiO2 nanoparticles and annealing at different temperatures to further tune their optical properties. Two distinct approaches for the fabrication of bulk THz optics from these novel materials were considered. First, THz cylindrical lenses of identical geometry but different refractive indices and focal lengths were produced using standard mechanical processing of opals, in order to highlight their compatibility with conventional technologies of bulk optics fabrication. Second, a THz axicone was made via direct sedimentation of aqueous colloidal suspension of SiO2 nanoparticles in the mold of geometry inverse to that of a desired optical shape, followed by annealing and polishing. The second approach has an advantage of being considerably less labor intensive, while capable of obtaining optical elements of complex geometries. Thus fabricated bulk THz optical elements were studied experimentally using continuous-wave THz imaging, and the results were compared with 2D and 3D numerical predictions based on the finite-difference time-domain and finite-element frequency-domain methods. Our findings highlight technological robustness of the developed THz optical material platform and, thus, open the door for creating a variety of bulk THz optical elements of complex shapes and widely-tunable optical performance.

© 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Optical Properties of Hyperosmotic Agents for Immersion Clearing of Tissues in Terahertz Spectroscopy

G. R. Musina, A. A. Gavdush, N. V. Chernomyrdin, I. N. Dolganova, V. E. Ulitko, O. P. Cherkasova, V. N. Kurlov, G. A. Komandin, I. V. Zhivotovskii, V. V. Tuchin,  K. I. Zaytsev

https://link.springer.com/article/10.1134/S0030400X20070279

We measured the transmission spectra of the most common hyperosmotic agents, such as pure glycerol, propylene glycol (PG), dimethyl sulfoxide (DMSO), polyethylene glycol (PEG) with molecular weights of 200, 300, 400, and 600 Da, their aqueous solutions, and aqueous solutions of sucrose, glucose, fructose, and dextran 40 and 70. The experiments were carried out using a THz pulsed spectrometer with an evacuated measuring compartment to eliminate the effect of water vapor on spectral measurements. We reconstructed the dielectric characteristics of hyperosmotic agents in the spectral range from 0.1 to 2.5 THz and plotted a dependence of the amplitude absorption coefficient on the concentration of the considered agents at a frequency of 0.5 THz. The results are useful for selecting optimal agents for immersion optical clearing in the THz range.

Abstract-A method for reconstruction of terahertz dielectric response of thin liquid samples

A. A. Gavdush,  V. E. Ulitko,  G. R. Musina, I. N. Dolganova,  N. V. Chernomyrdin,  V. N. Kurlov,  G. A. Komandin,  V. V. Tuchin,  K. I. Zaytsev,

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/11060/110601G/A-method-for-reconstruction-of-terahertz-dielectric-response-of-thin/10.1117/12.2527649.short

We developed a method for reconstructing the THz dielectric response of a thin liquid sample. A self-made sample cuvette was designed for the transmission-mode THz pulsed spectroscopy of liquids. Numerical simulations and theoretical studies of the proposed reconstruction procedure were performed in order to optimize the sample geometry and predict uncertainties in reconstructed dielectrical properties. A number of agents for immersion optical clearing of tissues was studied using the proposed method in the THz range. The developed method can be applied for all types of sufficiently transparent liquid samples.

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