Head of laboratory: PhD of Physics and Mathematics, Senior researcher Kuvondikov Vakhobjon phone: (+99871) 262 31 69 e-mail: Vahobjon87@gmail.com, kuvondikov@iplt.uz

Scientific directions of the laboratory:

• Fluorescence and photoacoustic spectroscopy of Solar energy conversion processes of photosynthesis.
• Nonlinear propagation of ultrashort laser pulses in optical fibers.
• Applications of laser technologies in medicine and agriculture.
• Investigation of optical, morphological and photovoltaic properties of organic and perovskite Solar cells.

Laboratory of Condensed Matter Optics of Arifov Institute of Ion-Plasma and Laser Technologies has many years of research experience in the field of laser physics and spectroscopy, interaction of laser radiation with biomolecules, as well as in the development of devices and devices based on them. The staffs of the laboratory studied the absorption-fluorescent characteristics of photosynthetic systems (photosynthetic membranes from plant leaves and photosynthetic bacteria, isolated supramolecular complexes of reaction centers and light-collecting antennas of photosynthesis, etc.). A spectrometer has been developed for use in studying the photosynthetic activity of a plant using a photoacoustic effect, as well as a device for determining the depth of penetration and absorption of laser radiation in living systems using a three-color RGB LED. The Group is also working for laser radiation to be used in medicine.

The staffs of the laboratory are also actively working in the field of laser physics, nonlinear optics and the interaction of laser radiation with matter. The physical processes occurring in optical fibers and interferometric fiber devices (single and double fiber loop, directional couplers in the form of two parallel fibers, two-core single-mode fibers, supercontinuum generation, nonlinear light switching, optical restriction, Kerr modulation of light, etc.) have been studied.

The staffs of the laboratory, in collaboration with scientists of the Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT), are implementing an international joint fundamental project "Flexible Organic Photovoltaics - a new convenient source of renewable energy" for 2021-2022. Students of bachelor's degree and Master's degree including 3 students of the National University of Uzbekistan named after Mirzo Ulugbek and Tashkent State Technical University named after Islam Karimov participate in the implementation of this project, perform their final qualification works and dissertations of Master's Degree.

The laboratory is equipped with a modern experimental base that allows conducting research at the level of modern standartds.

Scientific research of the laboratory's scientific and technical developments in the field of instrumentation is carried out in close cooperation with the Department of Chemistry of the University of Chicago, USA, (Prof. J. Norris), the University of Texas at Austin, USA, (Prof. I. Kholmanov), Northwestern Polytechnic University of China, (Prof. Huanhua Li), Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT), China (Prof. Shuguang Wen) Dongguk University, Seoul, Republic of Korea (Prof. T. Kang), University of Milan, Italy (Dr. S.Santabarbara), NGO "Polyus", IOF RAS (Russia), in which joint experiments were conducted with the participation of laboratory staffs in order to identify the nature and create new methods and instrumentation in various fields of physics.

Prof. Zakhidov E.A. conducts a seminar
at Bar-Ilan University (Israel)

Prof. Nematov Sh.K. at the
Polytechnicnical University of Milan (Italy)

A number of the laboratory's achievements in new high-tech developments were presented at the International Conferences such as "International Symposium on Semiconductors and Applied Physics" ISPSA-2014 (Jaju, Korea, 2012, 2014, 2016, 2018, 2022), in the International Symposiums in Milan (Italy) on biophotonics (Milan, 2016) and in Tel Aviv (Israel) on Nanomaterials (Tel Aviv, 2017).

Over the past 20 years, laboratory researchers have implemented many fundamental practical and innovative projects. In particular, such foreign projects as the US Civil Research Development Fund (CRDF), the Ukrainian Science and Technology Center (STCU) of the Swiss Science Foundation (SNSF) have been successfully implemented, which in total amount to 8 prestigious foundations.

Dissertations defended by laboratory staff in recent years:

2021 M.Kh. Imomov successfully defended his PhD dissertation on the topic "Optical spectroscopy of a nanostructured mixture of promising organic substances for solar cells" (scientific supervisor Doctor of Physics and Mathematics, Prof. E.A. Zakhidov).

2019 I.I. Tajibaev successfully defended his PhD dissertation on the topic "Interference fiber–optic systems for converting laser radiation parameters in the visible and near-infrared spectral regions" (scientific supervisor Doctor of Physics and Mathematics, Prof. Zakhidov E.A.).

2018 V.O. Kuvondikov successfully protected his PhD dissertation on the topic: "Fluorescent control of charge transfer processes in supramolecular systems of natural and artificial photosynthesis" (scientific supervisor Doctor of Physics and Mathematics, Prof. Nematov Sh.K.).

2015 Sh.K. Nematov successfully defended his doctoral dissertation on the topic "Spectral-kinetic characteristics of chlorophyll fluorescence in photosynthetic systems" (supervisor Doctor of Physics and Mathematics, Prof. Zakhidov E.A.).

Within the framework of the partnerships established by the laboratory with the PRC, laboratory employee A.A. Saparbayev became the winner of the TWAS competition and the Academy of Sciences of China announced for PhD courses. In 2020, he successfully defended his PhD dissertation at the Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT) Republic of China on the specialty of new biopolymer semiconductor materials for optoelectronic systems.

Currently, in the scientific laboratory of Condensed Matter Physics of Arifov Institute of Ion-Plasma and Laser Technologies, PhD student Nurumbetova L.R., Junior researchers Boynazarov I.R. and Ruziev F.M., Research assistants Turgunboev A.Y, Khidirov B. and Turakhodjaeva F.N. are actively working on their PhD dissertation. They also supervise the final qualification works of bachelors of TSTU, NUUz, TSPU (3 students in 2021 and 3 students in 2022) and masters students (8 in 2021 and 10 in 2022) who participate in the implementation of scientific, technical and innovative works, performed by the laboratory.

Fluorescence and photoacoustic spectroscopy of photosynthetic processes of solar energy conversion

In the laboratory of Condensed Matter Optics, the photosynthesis processes have been studied over the past two decades using fluorescence spectroscopy of chlorophylls and bacteriochlorophylls in plant leaves and photosynthetic bacteria. The physic and chemical conditions causing the dependence of the spectral-kinetic characteristics of fluorescence on temperature, illumination and water availability have been studied. Both intact natural systems (plant leaves and purple photosynthetic bacteria) and solutions of photosynthetic membranes isolated from them, reaction centers, light-collecting antennas, etc. by biochemical methods are considered.

A complex of experimental installations of laser fluorescence spectroscopy with high time resolution has been developed, with the help of which the fast kinetics of chlorophyll fluorescence, delayed fluorescence (DF) in the reaction centers of photosynthesis – the afterglow of chlorophyll due to the energy of reverse electron transfer along the charge transfer chain with characteristic times in the range of nano-micro- and milliseconds have been studied. The use of the strobe integration method at high pulse repetition rates allowed achieving the maximum sensitivity of the DF at low light intensities. It has been shown that the spectral-kinetic characteristics of fluorescence, as well as the dynamics of changes in DF, are an informative tool for studying the energy of photosynthesis, as well as identifying the causes of environmental conditions affecting various stages of photosynthesis.

The laboratory has a complex of modern equipment for studying the absorption-fluorescent characteristics of photosynthetic systems including laser sources of various spectral ranges and with different time characteristics (nonstop, pulse-periodic with durations of nano- pico- and femtoseconds). A highly sensitive registration system based on the BCI-280 boxcarintegrator (ZWG, Berlin, Germany) allows tracking the time profile of the studied pulse with picosecond resolution. An original setup has been created for studying DF with ultra-high sensitivity in a millisecond time interval.

The parameters of chlorophyll fluorescence associated with the efficiency of assimilation of absorbed solar radiation by cotton leaves can also be determined by the MINI PAM pulse amplitude modulation fluorometer (Waltz, Germany) available at the laboratory.

Fluorometer MINI PAM

This portable device with the ability to carry out up to 4000 measurements in the field without recharging and direct data transfer to a personal computer, allows fluorescent monitoring of plants in the field and comparatively study of genotypes with different photosynthetic properties.

The mechanisms providing very high efficiency of photosynthesis in the near-IR spectral region in bacterial photosynthesis has been studied by a scientific group together with the laboratory of Prof. J.Norris, University of Chicago (USA).

Jointly with Prof. P.Stamp, Polytechnic University of Zurich (Switzerland), and Prof. A.Masacci, National Scientific Center (Rome, Italy), a series of joint experiments of the effect of long-term water deficiency on the efficiency of photosynthesis in various genotypes of cotton in Switzerland (in phytotron) and Uzbekistan (in the field conditions) was conducted. It has been shown that water deficiency can cause increased photosynthetic activity to provide the plant with the necessary additional energy, and this property is inherent in all studied genotypes in the various degrees. According to the daily changes in the photosynthesis efficiency, the dynamics of photosynthesis photoinhibition was revealed; this is an effective mechanism for the energy dissipation of excessive light flux in the daytime, the development of this phenomenon depends on a degree of plant adaptation to the light.

Study of primary photoinduced photosynthesis processes and the impact of physical environmental conditions on them.

The laboratory has developed an exemplary version of the Analyzer Photosynthesis Efficiency APE-2 for fast and reliable evaluation of the efficiency of photochemical conversion of sunlight during photosynthesis in the leaves of various crops.

Analyzer Photosynthesis Efficiency APE-2

The use of low-frequency photoacoustic (FA) spectroscopy to study the processes of energy accumulation and thermal dissipation of light radiation makes it possible to identify various mechanisms of assimilation of light energy (photothermal, photobaric and photocomformational components) by frequency and time characteristics of the photoacoustic signal. For these purposes, the laboratory of Condensed Matter Optics has developed an original photoacoustic installation with high sensitivity at low frequencies using a gas-microphone recording scheme based on monochromatic light sources and tunable lasers.

The possibility of isolating the photothermal and photobaric components of the FA signal from a plant leaf is shown by studying its frequency characteristics. When light is applied, saturating photosynthesis, the photobaric component of the FA signal can be temporarily suppressed, which allows us to isolate and study photothermal relaxation.

At the same time, it is shown that high-intensity lighting can induce photoinactivation of the photosynthetic items which significantly reduces the work of its oxygen-releasing complex. Formulas describing changes in the FA signal at different illuminations of the photosynthetic system are obtained.

The lines of the frequency dependence of the FA signal in the absence of continuous saturating light (line a) and in the presence (line b) obtained in a leaf of light-loving cotton.

Laser technologies applied for photodynamic therapy

In recent years, along with the two most important areas of application of laser radiation in clinical practice, a new direction of modern medicine has appeared - photodynamic therapy (PDT). PDT is a fundamentally new method of malignant tumor treatment and is based on the ability of special photosensitizer molecules under laser irradiation to transfer nearby oxygen atoms into a singlet excited state with a highly cytotoxic effect. Selective accumulation of photosensitizer in cancerous cells makes it possible to destroy the latter by irradiating the corresponding parts of the human body with laser radiation and the fluorescence of the photosensitizer in the long–wavelength region accompanied by this allows diagnosing and localizing the area of the tumor location. Along with cancer PDT is also successfully used in antibacterial therapy, especially when infectious agents are resistant to antibacterial drugs.

Currently, the many scientific centers of the world has been actively searching for new substances that are prospective as photosensibilizers of PDT and studying their cytobiological, biochemical, and spectral-kinetic properties. The phenothiazine dye - methylene blue (MB) is characterized by the most important properties for PDT: low toxicity, selective accumulation in malignant cells, high quantum yield of singlet oxygen generation and a sufficiently long-wavelength position of the excitation band (665 nm) providing deep penetration of exciting radiation into tissues. The flat heterocyclic structure of the MB molecule causes intensive interaction with proteins, nucleic acids and high biological activity.