We have presented a detailed theoretical description of the optical coherence tomography. We demonstrate application of this model in simulations and compare it with experiments carried out. Agreement between our theory and experiments is obtained.

Interferometers with a low-coherent illumination allow non-contact measuring the rough surface relief or multilayer tissues by locating the visibility maxima of interference fringes. The problem is the light scattering by the surface to be evaluated; it is why the interference fringes are often distorted. Other problem consists in the need to process large amount of data obtained in optical coherence tomography (OCT) systems. We propose to use a stochastic fringe model and Kalman filtering method for noisy low-coherent fringe processing. A fringe signal value is predicted at the next discretization step using full information available before this step and the prediction error is used for dynamic correction of fringe envelope and phase. The advantages of Kalman filtering method consist in its noise-immunity, high-speed data processing and optimal evaluation of fringe parameters.

Effect of dextrans on optical property of blood in stasis and in flow was investigated with optical coherence tomography. The mechanisms for blood optical clearing are the characteristics of the types of dextrans employed and their concentrations. Among the substances applied, Dx500 at 0.5 gdl^-1 and 5 gdl^-1 are most effective in improving light penetration depth through the blood in stasis and in flow respectively. Optical clearing of blood was achieved by refractive index matching and aggregation of erythrocytes induced by dextrans.

New and fascinating field of highly scattering gain media, random lasers and the study of the behavior of such materials of biological significance is presented. Especially the study of the behavior of various fluorophores embedded in highly scattering matrices. The observed fluorescence signal of the fluorophore quenches in both temporal and spectral domains due to the intense scattering that the photons undergo. This happens when the excitation energy reaches and exceeds a threshold value. Above that value the narrowed fluorescence exhibits the same features as the excitation laser pulse. Lifetime in the order of 50 psec and spectral FWHM in the order of few nanometers are observed. For energies below the threshold value the amplification is negligible and the samples behave exactly as those without scatterers. As the excitation energy increases the laser action requirements are fulfilled and the sudden narrowing takes place. Similar studies are underway when various fluorophores are embedded in biological tissues. The final goal is to take advantage of this effect towards a more spatially and spectrally confined agent in Photodynamic Therapy of target tissue lesions on skin or other types of superficial lesions. Very promising in the field of skin PDT would be thin polymer sheets with various dyes, which could be applied directly on the lesion and allow the selection of different irradiation wavelengths using the same laser as excitation source. Thus, improving by far the efficiency of the destruction of different types of cancerous cells. In the biomedical arena, the materials high conversion efficiency per unit volume (≥ 50 percent in a 250 μm thickness) allows for wavelength-shifted catheters and laser creams, potentially useful for the removal of tattoos and other skin discolorations. In addition, random lasers can be used for wavelength shifting the installed base of lasers for other applications such as photodynamic therapy where narrow-band excitations are required for drugs such as benzoporphyrin derivatives (BPD). As far as detection is concerned random lasers could be implemented in various applications such as medical imaging. The combined use of these materials with chromophores that are selectively absorbed by malignant tumors and the narrowband emission along with the high-emitted intensity could boost the detection efficiency.

The aim of this study was to investigate the natural intrinsic fluorescence in sound and diseased human teeth and the correspondence of such autofluorescence to the stages of the dental lesions. Direct visual examination was used for comparison. Different stages of caries lesions are detected, by using a nitrogen laser (337 nm), light-emitting diode (LED) (440 nm) and argon laser (488 nm). Besides caries, there were investigated samples of the fluorosa dentis and odontolithiasis, for better determination of the influence of other teeth pathologies over the teeth autofluorescence spectra. There was observed a significant decrease in the intensity of the autofluorescence signal in the case of caries. The carious lesions revealed characteristic emission of endogenous fluorophores with fluorescence band in the red spectral region. Healthy hard dental tissue exhibited no emission bands in the red. An algorithm for early diagnosis is created on the basis of collected significant statistical material.

The autofluorescence spectra of hard dental tissues, both in normal and pathological areas were investigated in this study. The measurements were performed both on the intact hard tissues of the examined teeth, such as enamel, dentine, cementum, and root canal, and on the tissues pathologically affected by caries (superficial, intermediate, and deep). Various laser wavelengths (337 nm, 488 nm, and 514 nm) were used to irradiate the dental surfaces and a computer-controlled spectrograph captured the fluorescent spectra. The emission signals were stored, measured, analyzed and quantified in terms of wavelength distribution and the relative photon intensity. Results indicated that the fluorescent spectra from healthy enamel, dentine, and cementum were almost identical in form, depending on the excitation wavelength. The intact and affected hard tissues were greatly different in the integral fluorescent intensity. Healthy areas were found to produce the most pronounced fluorescent intensity, whereas the carious regions produced the weaker fluorescent intensity. Independently of the laser excitation wavelength, dentin regions were found to produce the most pronounced fluorescent intensity than any other dental component. The fluorescence signal of carious affected dental structure revealed a reed shifted spectral curve, more pronounced after 488 nm excitation. There was a pronounced red shift for deep caries (crown -- root caries), after ultraviolet laser excitation. Excitation with visible wavelengths did not produce such differences between intact and cervical, deep carious affected tissue. Using a monochromatic light source without any light output at the wavelengths of fluorescence, e.g. a laser with the appropriate filters, the difference in fluorescence between intact and carious enamel was generally easy to observe. Finally, we found that the blue line of an argon ion laser is preferable for superficial caries detection, while the ultraviolet emitting nitrogen laser induces better discrimination in deep caries diagnosis.

The method of laser induced fluorescence of the seawater was used for validation of satellite measurements of chlorophyll A concentrations in coastal water of the sea of Okhotsk during scientific cruise in summer 2001 year. Measurements were made by pumping laser fluorometer installed on the sailboard. The second harmonic of the Nd:YAG laser was used to induce the fluorescence spectra, scanning monochromator allows to measure the fluorescence itensity from 540 nm to 740 nm during about 1 minute. Measurements were done during the ship moving, the spatial resolution of chlorophyll A concentration determination was about 200 meters. The ship measurements were compared with chlorophyll A concentrations received by SeaWiFS (level 1a data) at the same time and area by using the global positioning system. The features of the fluorescence spectra were used to determinate the sea water areas where the satellite and fluorometer data were very closed.

Cytochrome c oxidase is considered as the photoacceptor when eukaryotic cells are exposed to monochromatic red to near-IR radiation. Five primary mechanisms are discussed: changes in the redox properties of the respiratory chain components following photoexcitation of their electronic states, NO release from catalytic center of cytochrome c oxidase, generation of singlet oxygen, localized transient heating of absorbing chromophores, in creased superoxide anion production with a subsequent increase in the concentration of H₂O₂. A cascade of reactions related to the alteration of cellular homeostasis parameters (pH_i, [Ca_i], cAMP, Eh, [ATP] and some others) is considered as a photosignal transduction and amplification chain in a cell (secondary mechanisms).

The field model of low-level optical radiation effect on a human organism is presented. In vivo and in vitro experiment results confirm this approach.

The work presents the results of the low-level laser therapy (LLLT) of two groups of volunteers with a variety of conditions performed with a GaAs-system. The volunteers were randomly selected among the patients who were usually treated by conventional therapy that included massage and acupuncture needles. The LLLT was proposed to the first group as extension of conventional treatment. The second group underwent only the LLLT. The effectiveness of the therapy was graded under four categories. Short-term and long-term side effects as well as conditions responding only to LLLT were recorded. The successful treatments were up to 70% for both groups, which coincided with the result of the control group treated by the conventional therapy. For optimization of the light delivery, the spatial maps of the absorbed dose in a homogeneous medium, both in the proximity of the light source and at a distance from it, were compared for collimated and divergent light beams using a reduced variance Monte-Carlo code.

The effect of XeCl laser radiation on carbonic anhydrase solution is studied. It is investigated that kinetics of protein aggregation is strongly influenced by both laser fluence and repetition rate. The theoretical model is constructed which allows one to explain qualitatively the features of experimental findings.

We have stated and analytically solved heat transfer equations for a multi-component biological tissue iluminated by a temporal delta-pulse at different heat exchange mechanisms between blood vessels and its surroundings of basic tissue and between the tissue as a whole and its ambient external medium. The contribution of each mechanism to temperature fields inside the tissue is studied in detail. Empirical constants of the mechanisms are estimated from rather strict and general viewpoints of thermal physics. Specific numerical values of the constants are given for air or water as the environment. The starting HTEs were substantially simplified by evaluating optical and thermal physical parameters of tissues to show that the tissue can be regarded as optically and thermally uniform with localized light absorption or additional heat sources in blood vessels. The thermal fuction of a human organism is approximated to include the boundary contact of a tissue with an ambient medium having a temperature other than that of the tissue. The applicability limits of the used 1D HTEs are discussed and substantiated for the estimations. Sample results illustrating temporal and spatial temperature distributions for convective and thermal conduction surface losses to the environment are given. It is shown, in particular, that the lower the volume content of blood vessels in tissue, the higher the temperature of the vessels and their tissue surroudings immediately after irradiation. The opposite situation occurs in a fraction of a millisecond after the irradiation, i.e. the tissue temperature increases with the volume content of the vessels.

After-burning/evaporation of destruction products in the course of laser ablation of biotissues was studied. The size distribution of ejected particles was measured and analyzed for different intensities of laser radiation. Evaporation was experimentally modelled by water aerosol flow subjected to intense 10.6 μm radiation of CO₂ laser. Numerical simulation was made for laser-induced changes of sizes and optical parameters of water and soot aerosols.

In this paper, experimental results of investigations of the physical mechanism of transcapillary exchange by the method of phase sensitive laser spectroscopy of light scattering are presented. Acoustic oscillations of the walls of microvessels (arterioles, capillaries, and venules) which provide transcapillary exchange have been detected for the first time.

The mechanism of channel punching in the heart muscle (myocardium) by a pulse of high-power CO₂ laser was studied. Water, PMMA and biotissue of animals were used as the models. Diagnostics of the punching process was performed by the methods of registration of sound vibrations in the air and back scattering of laser radiation. It has been revealed that at channel punching in various media, sound vibrations are excited in the spectrum region from 1 to 3.5 kHz, which are due to turbulent pulsation of vapor-drop flow ejected from the channel. The spectrum of acoustic vibrations depends on positions of the channel bottom and is sensitive to the boundary between the myocardial tissue and blood. The measurement of sound vibrations spectra can serve as the basis for diagnostics of the process of channel punching in myocardium.

The photodynamic activity of dibiotinylated aluminium sulphophthalocyanine in vitro and in vivo were studied. It was obtained that in vitro dibiotinylated aluminium sulphophthalocyanine provides the effective damage of small cell lung carcinoma OAT-75. In vivo dibiotinylated aluminium sulphophthalocyanine causes destruction of tumor (Erlich carcinoma), results in total necrosis of tumor tissue and expresses vascular damage (trombosis and destruction of vascular walls) even in concentration 0.25 mg/kg of a body weight.

High-power femtosecond laser pulses can lead to strong nonlinear interactions during the propagation through a medium. In air the well known self-guiding effect produces long intense and moderately ionized filaments, in which a broad white-light continuum from the near UV to the mid IR is generated. The forward directed white-light can be used to do range resolved broadband absorption measurements, which opens the way to a real multi-component lidar for the simultaneous detection of several trace gases. On the other hand, enhanced nonlinear scattering and characteristic emission from the filament region, as well as from the interaction of intense pulses with aerosols, can be observed. This opens perspectives towards a novel kind of analysis of atmospheric constituents, based upon nonlinear optics. Additionally, the conductivity of the filaments can be used for lightning control. Here we present the basic concepts of the femtosecond lidar, laboratory experiments and recent results of atmospheric measurements.

Technical potentialities of incoherent spatial filters for analyzing the brightness function of a scattering volume in the lidar observation plane are discussed. Such an analysis allows one to receive additional information on the multiply scattered component of a lidar signal. To this end, incoherent spatial filters limiting the receiving flux of a scattered radiation in the receiving objective focal plane are used. It is shown, however, that the potentialities of this analysis are limited.

Spectral dynamics of a cw Co:MgF₂ laser with intracavity absorption is recorded in the spectral range around 2 μm. Sensitivity to intracavity absorption corresponds to the absorption path length of 1200 km. New absorption lines of methane are detected.

The capabilities of different molecular gas lasers in infrared absorption diagnostics of multicomponent mixture are evaluated and compared. Extended sets of vibration-rotational emission lines are used for the following lasers: CO₂, HF, DF, NH₃, N₂O and CO (including fundamental and first overtone transitions). Analytical frequencies are selected for all indicated lasers using spectroscopic databases in order to detect organic and inorganic pollutants using either low- or high-resolution spectra. Comparison of absorption in the atmosphere is made for frequencies of different lasers. Absorption spectra are simulated for 38 component gas mixture. Quantitative parameters characterizing the sensitivity and the selectivity of specific gas detection are calculated and compared: minimum detectable concentration, partial sensitivity, partial selectivity. It is found that NH₃ and CO lasers presently have the best spectroscopic detection characteristics.

In the paper there is considered a technique for the remote determination of scattering media optical characteristics based upon the concept of absence of a priori information. This technique allows one to eliminate instrumental errors caused by instability of measuring system parameters. Accuracy characteristics of the proposed technique have been evaluated.

The principles of development of "calibration-free" optoelectronic systems of environmental diagnostics are considered. These systems eliminate as much as possible methodical errors caused by the changes of instrumental constants of emitting-receiving and recording blocks, by the pollution of optical surfaces, etc. The evaluation of accuracy of proposed methods was carried out.

The C₂ abundance in flames at atmospheric pressure is reported for three fuel-rich combustion environments: acetylene/oxygen, Liquid Petroleum Gas (LPG)/air and methane/air flames. Measurements have been based on spectrographic and two-dimensional Laser-Induced Fluorescence (LIF) of the Δv = -1 d³II_g-a³II_u band. The oxyacetylene flame was utilized to establish a comparison with literature data and absolute values, calibrated through Rayleigh scattering, were found to be distributed within the 10¹⁴ cm^-3 range. The induced emission from two Bunsen flames fed with LPG/air or methane/air was also investigated. Accumulated acquisitions were necessary to detect small C₂ quantities in the order of 10¹⁰ cm^-3 concentrated on the flame front.

Noisy interferometric signals and distorted interference fringe patterns analysis is very important for solving problems of metrology and nondestructive testing. In this paper the possibilities of the new nonlinear locally-adaptive filtering method were explored. This method can be used for preliminary noise suppression of fringe patterns at phase retrieval and for extreme lines location. It was verified experimentally high noise-immunity of the method proposed when processing real-obtained noisy distorted fringe patterns.

A possibility of live fringe-pattern phase restorative by means of estimates of separate lines or sections of interferogram is submitted. It is possible if the phase is accepted the monotonous function in each section of interferogram. Thus, realization of on-line interferogram demodulation is possible and, besides, the fringe-pattern vibration effect is reduced.

Laser remote sensing of water, and the use of laser-induced fluorescence (LIF) in particular, are widely applied for Ocean investigations. Integration of the image-forming channel in such systems considerably extends the scope of these investigations, which is of great importance from various points of view. An experimental setup is created, with the help of which series of experiments have been carried out on the Lake Sevan. Test objects' images of different sizes and different reflection coefficients, located at various depths, for various receiver-transmitter fields of view were obtained. Corresponding dependences of reflected signal value and image contrast on water depths were also obtained. The investigations showed a 1.5 - 2 times increase of the object visibility limit depth as compared with the white disk visibility. Water transparency data obtained by these results coincide with those obtained with the use of the white disk. The measurements were further carried out under laboratory conditions in a 33 m pipe, filled with water initial characteristics of which were changed. Dependences of the reflected signal value, both from the depth and water transparency were obtained for various objects.

The Laser-Induced Breakdown Spectroscopy (LIBS) method was applied for detection of phytoplankton and marine water elemental composition. The results of the sea water quality monitoring and phytoplankton element composition measuring obtained in the Okhotsk coastal sea water during scientific research expedition in 2000-2001 years are described.

First experimental results on optical coherence tomography (OCT) imaging of internal structure of plant tissues and in situ OCT monitoring of plant tissue regeneration at different water supply are reported. The OCT images are a map of backscattering coefficient 200 x 200 pixels, 1.5 mm along plant surface and up to 2 mm in depth (by analogy with ultrasound B-scan). Experiments for evaluating OCT capabilities were performed on Tradescantia blossfeldiana Mild. Using OCT device, in vivo images of plant tissues were acquired with a spatial resolution of 15 μm. These OCT images correlate with standard microscopy data from the same tissue regions. Since incident light power at a wavelength of 1.3 μm is as low as 0.5 mW, two-dimensional OCT images can be obtained directly on an intact plant not damaging it. Acquisition time for a 2D image is 1-3 s. OCT enables effective monitoring of fast reactions in plants at different water supply.

The capabilities of laser-induced breakdown spectroscopy (LIBS) for analysis of water samples with low energy laser pulses was investigated using 355 nm, 10 ns pulses with energies from 3.5 to 100 mJ. In order to optimize the detection limit, the spatial and temporal dependence of the line emission from a sodium solution water jet target in air has been measured, allowing the identification of optimum gating time and observation position for sodium. Careful characterization of the background noise sources in the LIBS detection system has been undertaken, including the continuum emission from the plasma, dark current in the detector array and electron emission noise in the image intensifier. The energy dependence of the limit of detection for sodium in water has been investigated. Single shot detection limits for sodium have been measured ranging from 2 ppm to 200 ppm for laser pulse energies of 100 mJ to 3.5 mJ respectively. For aluminium, the detection limits are over an order of magnitude poorer than for sodium.

The effects of surface waves on laser beam transmission through the sea surface are experimentaly examined. The purpose is to obtain experimental data for comparison with laser propagation models. Simultaneous measurements of the time and space variability of the air-sea interface are performed. A submerged screen, filmed by an underwater video camera, is used to measure the downwelling irradiance profiles. The measurements are made in calm winds, in a sheltered harbor environment. Calibrated values of downwelling irradiance are obtained by reference measurements in laboratory. Two significant consequences of transmission through the sea surface are investigated: beam width at different depths averaged over several surface wave periods, and surfce wave focusing or defocusing quantified by the irradiance fractional fluctuations (standard deviation divided by the mean). We compare the irradiance fractional fluctuations from our experiment with published data from underwater sunlight measurements and from laser beam simulations. The irradiance fractional fluctuations show a near-surface maximum and decay with depth. Low wind speed is expected to increase the fractional fluctuations caused by wave focusing effects. Our measurements qualitatively agree with the compared data, but exhibit larger fractional fluctuations.

LIF spectroscopy is now widely used for measuring of the chlorophyll a concentration in the sea water. The investigations for the phytoplankton community condition monitoring (estimation of the photosynthetic activity of the phytoplankton cells) were carried out by LIF method during last years. In our measurements we used a laser fluorometer to measure the laser-induced chlorophyll fluorescence. The laser fluorometer allowed us to measure LIF spectra from the moving ship.

Laser-Induced Incandescence studies of graphite aerosols show that great care has to be taken in interpreting Laser-Induced Incandescence (LII) data from gas turbine exhausts. In principle, particle volume fraction, information on particle size, chemical composition, and physical and chemical properties of the exhaust gas is obtainable by LII without the need for a physical probe in the exhaust. However, much about the way in which laser heated particles interact with exhaust gases has yet to be discovered.

A polydispersive water aerosol model is developed in the frame of a one parameter model of turbulence in the wake behind large civil aircraft. A possibility is considered to create a clearing channel in the condensation trail (contrail) by a laser beam. Relations are derived between contrail parameters, clearing channel parameters and parameters at the engine nozzle section for different atmosphere conditions in cruiser. As an example contrails behind aircraft IL-86 and IL-96 are considered.

The ENEA Lidar fluorosensor apparatus take part to three marine campaigns in the South-western Ross Sea and along the Southern Ocean transects up-to New Zealand, revealing the bio-optical peculiarity of coastal zones and seasonal changes encountered. The investigated transects belonged to the ship course during the XIII (Nov. '97 - Jan. '98), XV (Jan. - Feb. '00) and XVI (Jan. - Feb. '01) Italian Antarctic expeditions. Various seasonal stages (pre or post-bloom phenomena, nutrients availability) of seawaters and major biological changes (different dominant phytoplankton species, relevant photosynthetic activity) have been already identified as a final result of the three-annual monitoring activity. Surface chlorophyll and CDOM fluorescence data, collected during the XIII and XVI oceanographic campaign, were used to be compared to 8-day L3 SeaWiFS data products and to tune the bio-optical chlorophyll-a algorithm.

A description of Siberian Lidar Station in Tomsk, created for the purposes of remote optical sensing of the middle atmosphere, is given. Results of multiyear observations of stratospheric ozone and aerosols at Siberian Lidar Station are discussed.