Victoria Atanassova

@issp.bas.bg

Laser, atomic, molecular and plasma physics
Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences

Victoria Atanassova


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https://researchid.co/vatanassova
My professional background encompasses extensive research in the application of advanced optoelectronic techniques for the preservation of cultural heritage, with a primary focus on laser cleaning, material characterization, and identification through various methods such as laser-induced breakdown spectroscopy, Fourier-transformed infrared spectroscopy, colorimetry, etc. My research portfolio extends to diverse materials, including contemporary artwork, archaeological ceramics, stone, metal, and more. In addition, I have a research interest in the application of ultra-short laser pulses. My work extends to the modification of optical coatings, polymers, and various materials, with practical applications in diverse fields such as biomedicine, optical industry, green technologies, and many more.

EDUCATION

2012-2017 - PhD in wave physics at Institute of Solid State Physics, Bulgarian Academy of Sciences
2010-2012 - Master in Quantum Electronics and Laser Equipment at Faculty of Physics, Sofia University "St. Kliment Ohridski"
2006-2010 - Bachelor in Physics at Faculty of Physics, Sofia University "St. Kliment Ohridski"

RESEARCH, TEACHING, or OTHER INTERESTS

Multidisciplinary, Atomic and Molecular Physics, and Optics, Physics and Astronomy, Conservation
18

Scopus Publications

Scopus Publications

  • Sub-Ablative Femtosecond Laser Modification of the Nonlinear Optical Response of Amorphous TiO2 Thin Films
    Victoria Atanassova, Georgi Yankov, Krum Shumanov, Stefan Karatodorov, Ilko Miloushev, et al.
    Coatings, 2026
    Femtosecond laser processing has emerged as a promising post-deposition method for tailoring the properties of dielectric thin films, offering localized modification without thermal damage. This study investigates the effect of sub-ablative femtosecond laser irradiation on the nonlinear optical response of a TiO2 single-layer coating deposited on soda-lime glass by electron-beam evaporation. The coating was modified using 35 fs pulses at 800 nm delivered at a repetition rate of 1 kHz and a fluence of 0.083 J/cm2 while varying the number of pulses per spot. The effective nonlinear refractive index (n2,eff) and effective nonlinear absorption coefficient (βeff) were measured using the z-scan technique with femtosecond excitation. The as-deposited TiO2 coating exhibited a negative effective nonlinear refractive index, signifying a self-defocusing nonlinear response, while femtosecond laser irradiation leads to pronounced changes in the effective nonlinear parameters. An increase in the magnitude of both effective nonlinear coefficients and a reversal of the sign of the effective nonlinear refractive index are experimentally observed after irradiation with higher pulse numbers. These findings provide experimental evidence that sub-ablative femtosecond laser processing can be used as a post-deposition tool to control the nonlinear optical response of TiO2 thin films.
  • Identification of Mineral Pigments on Red- and Dark-Decorated Prehistoric Pottery from Bulgaria
    Vani Tankova, Victoria Atanassova, Valentin Mihailov, Angelina Pirovska
    Minerals, 2025
    Identifying the mineral pigments used in the decoration of prehistoric pottery is a significant step for understanding the evolution of the technological practices over time. On the Balkan Peninsula during late prehistory, the techniques used for red and dark-colored decorations underwent a significant transformation. In the Early Neolithic period, pottery was often decorated with dark-toned paints, ranging from deep red to brown. However, this approach declined noticeably during the Chalcolithic period, when red pigment pseudo-incrustation became the predominant decorative method. This study aims to identify the mineral pigments used in red and dark decorations on Neolithic and Chalcolithic pottery from Bulgaria and to trace possible technological, regional, or chronological variations in their composition. A total of 34 ceramic sherds, decorated in shades from red to brown and black, were analyzed using two complementary spectroscopic techniques: laser-induced breakdown spectroscopy (LIBS) and Fourier-transform infrared spectroscopy (FTIR). LIBS data were further evaluated using principal component analysis (PCA) to classify materials based on elemental composition. The results indicate that red decorations are consistently composed of hematite and remain compositionally stable regardless of the region, time period, or application technique. In contrast, dark decorations contain various combinations of iron oxides (magnetite and hematite) and manganese oxides, often including barium-rich manganese compounds—potentially indicating pigment provenance. Additionally, the dark decorations display regional differences.
  • Investigation of the Nonlinear Optical Properties of Silk Fibroin (SF) Using the Z-Scan Method
    Georgi Yankov, Victoria Atanassova, Stefan Karatodorov, Radostin Stefanov, Krum Shumanov, et al.
    Materials, 2025
    Silk fibroin (SF), the primary protein in silkworm silk, has emerged as a promising organic nonlinear optical material due to its unique combination of optical transparency, biocompatibility, and environmental sustainability. In this study, we investigate the nonlinear optical properties of SF thin films using the z-scan technique with femtosecond laser pulses (35 fs, 800 nm, 1 kHz). Our results reveal a strong self-defocusing effect (negative nonlinear refractive index) and significant multiphoton absorption, demonstrating SF’s tunable nonlinear response. Additionally, optical transmittance measurements confirm SF’s partial transparency in the deep UV region, enhancing its potential for second-harmonic generation (SHG) and efficient light frequency conversion. These findings address a key knowledge gap in nonlinear optics, positioning SF as a versatile biopolymer for advanced photonic applications.
  • Combined spectroscopic approach for identification of mineral pigments in decoration of Neolithic pottery from the Western Bulgaria region
    Vani Tankova, Victoria Atanassova, Angelina Pirovska, Valentin Mihailov
    Optical and Quantum Electronics, 2024
  • Spectroscopic Identification of Mineral Pigments in White Decorated Prehistoric Pottery from Bulgaria
    Vani Tankova, Victoria Atanassova, Valentin Mihailov, Angelina Pirovska
    Minerals, 2024
    In the prehistoric period on the Balkan Peninsula, the technology of white decoration underwent a drastic change. At the beginning of the Neolithic white pigment was applied as paint on a polished surface. At the end of the epoch, white paste was inlaid in incised channels on the surfaces of vessels. This study is focused on the identification of mineral pigments used for white decoration of Neolithic and Chalcolithic pottery from the territory of Bulgaria. The aim of this work is to answer the question of whether the composition of the white pigment varies according to the technique of decoration (paint and inlay). A set of 41 pottery fragments from 11 archaeological sites on the territory of Bulgaria was analyzed utilizing two spectroscopic techniques: laser-induced breakdown spectroscopy (LIBS) and Fourier-transform infrared spectroscopy (FTIR). Additionally, the experimental data from the LIBS were statistically treated with the multivariate technique, principal component analysis (PCA). The results from the spectral analysis indicated that the main constituent in the white decorated sherds is calcite in various combinations with carrier materials like quartz, feldspars, and metal oxides. The statistical analysis revealed that the primal constituent in the inlaid sherds is calcite while in the painted part, the carrier material is dominant. In some particular sherds, gypsum, hydroxylapatite, kaolinite, and aragonite were also detected.
  • Spectroscopic Study of White Pigments in the Decoration of Neolithic Pottery in the Region of the Thracian Valley, Bulgaria
    Victoria Atanassova, Vani Tankova, Valentin Mihailov, Angelina Pirovska
    Minerals, 2024
    Throughout history, ceramics have been the most abundant artifacts in archaeological discoveries. Within the Neolithic period in present-day Bulgaria, skilled artisans applied additional materials to decorate their pottery, evolving in composition and application techniques such as painting or incrustation. This study is focused on the investigation of white pigments used in decorating Early and Late Neolithic pottery from Madzherito, Kaloyanovets, and Hadzhidimitrovo—archaeological sites located in the Thracian Valley, Central South Bulgaria, affiliated with the cultural groups of Karanovo I and IV. Thirteen ceramic sherds were investigated through archaeometric techniques, including Fourier-transformed infrared spectroscopy in attenuated total reflection mode (ATR-FTIR) and laser-induced breakdown spectroscopy (LIBS). LIBS data underwent further analysis using principal component analysis (PCA). The results revealed that calcite, enriched with diverse fillers like quartz, clays, feldspars, and metal oxides, was the primary raw material for white decoration throughout the entire period. Talc emerged as an addition to calcite in the paint of two Early Neolithic sherds. The presence of hydroxyapatite and kaolinite in Late Neolithic pottery was also observed. The inclusion of supplementary ingredients in the primary formula for crafting white decorations signifies either the emergence of novel trends in manufacturing techniques or serves as evidence of vessels imported from adjacent territories.
  • Photonic Applications for Restoration and Conservation of 19th Century Polychrome Religious Wooden Artworks
    Victoria Atanassova, Monica Dinu, Sultana-Ruxandra Polizu, Roxana Radvan
    Coatings, 2023
    The present paper reports the multi-analytical approach for the removal of thick layers of metallic overpaints from a Brancovan iconostasis of the “Holy Trinity” church in Măgureni, România, which was built in 1694. After a restoration procedure at the beginning of the 20th century, the polychrome sculpture of the frame, which was initially gilded with a thin silver foil, was covered with a thick metallic overpaint layer imitating silver and gold. Currently, the conservation project of the church is focused on restoring the original aspect; thus, the overpainting that presented strong oxidation and soiling was removed. The adopted conservation methodology involved physicochemical characterization of the pictorial layers via optical microscopy, laser-induced breakdown spectroscopy, and Fourier-transform infrared spectroscopy, followed by the removal of the overpaints. The cleaning tests were performed by evaluating several methods in order to find the proper regime that would help preserve as much of the underlying polychrome layers as possible. Based on the tests, it was decided that the best solution was to use laser cleaning for the rough removal of the metallic paint overlayers and finalizing with chemical cleaning.
  • Brackish and Hypersaline Lakes as Potential Reservoir for Enzymes Involved in Decomposition of Organic Materials on Frescoes
    Ioana Gomoiu, Roxana Cojoc, Robert Ruginescu, Simona Neagu, Madalin Enache, et al.
    Fermentation, 2022
    This study highlights the decomposing role through the hydrolytic activities of fungi isolated from natural environments represented by brackish and hypersaline lakes in Romania. Novel strains belonging to the Penicillium, Aspergillus, and Emericellopsis genera were isolated and screened for the ability to produce extracellular hydrolytic enzymes, i.e., proteases, lipases, amylases, cellulases, xylanases, and pectinases. According to salt requirements, they were classified as moderate halophilic and halotolerant strains. Agar plate-based assays with Tween 80, slide cultures with organic deposits, and quantitative evaluation allowed the selection of Aspergillus sp. BSL 2-2, Penicillium sp. BSL 3-2, and Emericellopsis sp. MM2 as potentially good decomposers of organic matter not only in lakes but also on deposits covering the mural paintings. Experiments performed on painted experimental models revealed that only Penicillium sp. BSL 3-2 decomposed Paraloid B72, transparent dispersion of casein, beeswax, sunflower oil, and soot. Moreover, using microscopic, spectroscopic, and imaging methods, it was proved the efficiency of Penicillium sp. BSL 3-2 for decomposition of organic deposits artificially applied on frescoes fragments.
  • ON THE ARTISTIC MATERIALS OF TWO 19th CENTURY WOODEN ICONS FROM "ANNUNCIATION" CHURCH IN GALAȚI, ROMANIA
    UPB Scientific Bulletin Series A Applied Mathematics and Physics, 2022
  • Laser removal of marker tags from a contemporary graffiti painting
    V Atanassova, L Ghervase, I M Cortea
    Journal of Physics Conference Series, 2021
    This contribution presents a study on the efficiency of the laser removal of black permanent marker tags from a contemporary graffiti painting. The effect of two wavelengths – 1064 nm and 532 nm, on the marker inks and the graffiti paints was investigated using optical microscopy and colorimetric measurements. Preliminary characterization of the marker inks and the paints by FTIR and XRF analyses was also performed. The results confirm that the materials’ response to laser radiation depends on their particular chemical composition.
  • Multi-analytical approach for characterization of archaeological pottery excavated in the Early-Neolithic settlement of Chavdar, Bulgaria
    Victoria Atanassova, Luminița Ghervase, Ioana Maria Cortea, Valentin Mihailov, Vani Tankova, et al.
    Spectroscopy Letters, 2021
  • Aspects of laser cleaning efficiency for contemporary artworks restoration
    UPB Scientific Bulletin Series A Applied Mathematics and Physics, 2020
  • Laser-Assisted removal of graffiti paint on stone: Potential use in the restoration of cultural heritage monuments
    Bridging Science and Heritage in the Balkans Studies in Archaeometry and Cultural Heritage Restoration and Conservation, 2019
  • Selective laser cleaning of corroded metal objects
    Victoria Atanassova, Ivan Kostadinov, Petya Penkova
    Aip Conference Proceedings, 2019
  • Laser removal of chlorine from historical metallic objects
    Victoria Atanassova, Ivan Kostadinov, Stefan Karatodorov, Georgi Avdeev, Petya Penkova
    Proceedings of SPIE the International Society for Optical Engineering, 2019
  • Laser cleaning of graffiti spray paints on marble, limestone and granite
    Graffiti Vandalism Street Art and Cultural Significance, 2018
  • Laser cleaning of different surfaces by copper bromide vapour laser: Application for cultural heritage preservation
    Comptes Rendus De L Academie Bulgare Des Sciences, 2017
  • Laser cleaning of graffiti on stone
    Victoria Atanassova, Ivan Kostadinov, Peter Zahariev, Margarita Grozeva, Ilko Miloushev
    Proceedings of SPIE the International Society for Optical Engineering, 2017