ნინო ფონჯავიძე

Results: We have investigated penetration of NIR through the prostate tissue. It was shown that NIR of 850 nm has highest penetration. Infrared image of noncancerous prostate represents picture with approximately even brightness. However obtained near-infrared images of the cancerous outgrowths of the prostate revealed dense and dark foci, which proved to be malignancy on pathology (adenocarcinoma, Gleason score 6[3+3] in 7 cases and adenocarcinoma, Gleason score 7[3+4] in 3 cases). At brighter areas the pathology report did not reveal the presence of malignant cells. Obtained IR images give opportunity to distinguish prostate cancerous outgrowth with the dimensions of several millimeter. 

A new type of flexible cholesteric liquid crystal mirror is presented. The simple and effective method for the deposition of a cholesteric mixture on a paper substrate and the particular design of the device give a homogeneous alignment of the cholesteric texture providing mirrors with an intense and uniform light reflectance. A desired polarization state for the reflected light, linear or circular, can be easily obtained varying the thickness and optical anisotropy of the polymer cover film. By using non-azobenzene based photosensitive materials a permanent array of RGB mirrors with high reflectivity can be obtained on the same device. Paper like reflective mirrors are versatile and they can find applications in reflective displays, adaptive optics, UV detectors and dosimeters, information recording, medicine and IR converters.

By quasi-chemical reaction method for FeTiO3 material in oxygen atmosphere, electron and hole concentrations for broad range of oxygen partial pressure have been calculated. Oxygen pressures, at which electrical and hole conductivity can be achieved, were estimated. Thin layers of FeTiO3 have been grown on transparent Al2O3 (0001) substrates by pulsed laser deposition technique at different oxygen partial pressures. Structural, optical, and electrical properties have been studied for these samples. By special post-annealing treatment, the conductivity type inversion from p to n has been achieved as predicted by our thermodynamic analysis.

Penetration of near infrared radiation (NIR) through biological tissues (human wrist, muscle and skin of hen, muscle of mollusk) was studied. The possibilities of visualizing various objects within biological tissues were examined. It is found that: (a) it is possible to see small objects with millimeter and sub-millimeter dimensions; and (b) by using NIR rays it is possible to distinguish different parts of small homogeneous biological tissues. NIR can be a possible tool in the near future to visualize millimeter size cancerous outgrowths located inside human body cavities. It will enable diagnosis of cancer at an early stage of development.

Measuring temperatures at small scales, especially around nanoparticles, is a crucial step for a variety of applications in biomedicine and in optics. Here, we report on a novel method to map temperature in the medium surrounding silver nanoparticles dispersing them in a thermochromic mixture prepared using an organic dye and a polymer. When the nanocomposite is irradiated with visible light, nanoparticles convert light into heat and the nanocomposite changes its colour. The temperature around silver nanoparticles can be, then, easily evaluated from this colour variation. The proposed method can be implemented in temperature monitoring devices of the nanoparticles surrounding media.

A few microns thick layer of an optically activecholesteric liquid crystal is realized by using a photoiso-merizable nematic component and a chiral dopant. It isshown that such a photosensitive optically active mediumcan be used as a holographic material for optical informa-tion and dynamic grating recording. The photo-inducedgratings are written by exploiting the light-induced pho-toisomerization phase transition from an optically activechiral liquid crystal to an isotropic liquid, which resultsin the rotation of the light polarization plane from 90 to0 degrees and corresponding to maximum, respectively,zero transmittance. The results highlight applications inthe eld of optical storage by the recording of static grat-ings, as well as in the eld of nonlinear beam-coupling viathe holographic writing of dynamic gratings

In this work, we demonstrate micro resonators made of liquid crystal blue phase (BP) microspheres, embedded in a polymer/water matrix. The omnidirectional 3D lasing from BPII and BPI microspheres and the temperature-controlled laser tuning within the range of 55 nm from the BPI microspheres were observed for the first time. The potential applications of BPs microlasers range from temperature-controllable, omnidirectional, coherent light micro sources to informational displays and micro sensing devices.

A thin layer of the photosensitive cholesteric liquid crystal possessing a high value of the optical activity is studied. Reversible change in the optical activity controlled by two light emission diodes (LEDs) with different emission wavelengths is applied for information recording. The behavior of this structure under exposure to UV and blue light is investigated. A smooth decrease in optical activity caused by the UV light resulting in a change in the color of the structure between crossed polarizers is obtained. The reverse process occurs under exposure to the blue light. On the basis of the obtained results, two methods of optical information recording in such a layer have been demonstrated.

We have prepared the liquid crystal blue phase (BP) microdroplets emulsified in the glycerol environment and investigated their electro-optical properties upon the applied electric field. We showed that the lasing from the supercooled luminescent dye-doped BPI microdroplets can be controlled electrically. When the electric field intensity is increased, the lasing intensity is increased too along with the linewidth that decreases from 6 to 2.5 nm. Besides, the laser lines were shifted toward the shorter wavelength by 11 nm. All effects were achieved via electric field-stimulated structural and symmetrical modification of BPI microdroplets, resulting in their optical anisotropy and birefringence. Luminescent dye-doped liquid crystal blue phase-based microdroplets can find applications as electrically controlled microlaser sources for microphotonics and environmental sensing.