Determination of microphysical parameters of erythrocytes in human blood from laser radiation scattering

We have studied the sensitivity of the correlation between the unidirectional scattering coefficients β(θ) and the microphysical parameters of erythrocytes in human blood the number concentration (N) and the volume concentration (C_V), the modal radius (r), and the half-width (Δr) of the size distribution function of the erythrocytes, the real part of their refractive indices n) to variations of the latter in the ranges of their possible values at wavelengths λ = 0.3–1.2 μm. We have obtained the multiple regression equations for the microphysical parameters and β(θ) in the transparency window of blood (λ = 0.65 μm). We have shown that the procedure for determining the microphysical parameters, based on these equations, allows us to rapidly determine the microphysical parameters rapidly and highly accurately within their possible ranges. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 652–658, September–October, 2007.     

Biophotonics of the interaction of low-intensity laser radiation with blood erythrocytes

We have studied experimentally how optical radiation affects the neutralization of the toxic action of heavy metals and harmful chemical compounds (ecotoxicants) on the oxygen-transport function of blood erythrocytes. It has been found that the optical radiation has a stabilizing effect and prevents lowering the erythrocyte concentration in the presence of phenol and heavy metals in blood. We have studied the neutralization efficiency of the toxic action of ecotoxicants in relation to the laser irradiation time. The obtained data on the effect of the laser radiation on the thermal denaturation of hemoglobin and erythrocytes yield the scientific substantiation to the development of the optical method for the use in medicine upon drawing and conserving donor blood. We have shown that the obtained data can be used in medicine for improving the reliability of conditions of conservation and storage of donor blood, as well as for preventing the toxic action of harmful chemical compounds in the environment.     

Optical methods of laser radar field processing

The book describes modern methods of receiving laser signals, viz., by interferometry, by nonlinear optics, by laser amplification, and by heterodyne mixing. The theory of these methods is considered as applied to the problem of laser radars. Investigated in detail are features such as the resolving power of interferometry and nonlinear-optics method, the efficiency of parametric conversion of laser signals, the sensitivity of laser amplifiers, and problems of optimal heterodyne detection. Methods of speckle interferometry and adaptive optics are described. The book is aimed at a large circle of scientists and engineers active in the problem of recording of laser signals, as well as to students in advanced courses of the corresponding specialties.N. D. Ustinov — General Editor.Translated from Metody Obrabotki Opticheskikh Polei v Lazernoi Lokatsii, pp. 3–269, 1983.     

Photodestructive effect of IR laser radiation on the cornea

A mathematical model of the photodestructive effect of high-power IR laser radiation on cornea tissues is presented. The threshold energy exposure is calculated as a function of the wavelength and the laser pulse duration in the range 10^?5–10^?1 s under the assumption that the irreversible primary changes in the structure of tissues have a thermochemical nature. The adequacy of the model is supported by comparison of the results of calculations with a great body of experimental data available in the literature. The model is oriented for use in designing medical equipment (for example, for the refraction correction by the thermal keratoplasty method) and in refining the operating laser safety standards.     

Optical feedback effect on bistable laser diodes

The optical feedback effect on multi-section bistable laser diode characteristics, especially on light/current hysteresis, has been studied. A decrease in the bistable laser diode hysteresis width under optical feedback was observed for the first time. A theoretical analysis has been carried out by solving carrier density rate equations, combined with the light-field equation. The analysis shows that the observed hysteresis width decrease is due to the phase detuning, which is governed by the difference between the values of the α-parameters (line-width enhancement factors) in the gain section and the loss section.     

Physical methods for studying the effect of europium ions on lysozyme solutions

Metals play an important role in a human organism. Concentrations of metals, particularly, heavy metals, exceeding the maximum allowable level in the organism are dangerous for persons. At present, it is of topical interest to study molecular mechanisms of the effect of heavy metal ions on biological fluids, for instance, blood, and to develop sufficiently simple and reliable physical methods for environmental monitoring of the occurrence of heavy metals in natural environments, in the first place, in water.     

Optical properties of excimers in the field of intense laser radiation

The specific features of the luminescence of excimer molecules are analyzed within the model of a purely repulsive potential for the ground state in the field of intense laser radiation with due regard for the squeezed vibrational states. It is demonstrated that the luminescence band with the inclusion of the equilibrium phonons can be represented by a broad structureless asymmetric bell-shaped curve. The squeezed vibrational states substantially affect the frequency dependence of the luminescence intensity; more specifically, the luminescence band exhibits two maxima in the case of strong electron-phonon coupling. The stabilization of an excited electronic state in the course of luminescence at the fundamental frequency and generation of higher optical harmonics in the field of intense laser radiation is discussed.     

激光脉冲对内层等离子体辐射源的影响

本文的基本思想是设计双层金铝薄膜靶以检测激光脉冲宽度与等离子体消融深度的关系,找出有效的等离子体加热方法以产生更强更亮的等离子体辐射源.由于有预脉冲激光的存在,表层金薄膜首先被消融,由主脉冲携带的大能量就能较易穿过表层金等离子体将能量聚焦在内层铝靶上,由此产生内层高温等离子体.又由于外层低温等离子体存在,其将有效的阻碍内高温等离子体因膨胀而引起的能量损失.对无预脉冲而言,直接入射激光能量都沉积在靶表层形成表层高温等离子体.但是激光直接入射而产生的等离子体辐射总强度只比由预脉冲情况下产生的金等离子体辐射强度增加15%.而预脉冲能量只占激光总能量的2%.实验结果显示Al光谱线主要来自类氢,类氦离子跃迁.Au等离子体光谱线主要来自它的N带,O带和P带谱.我们也观察到一个明显的软X射线短波发射极限.所有结果显示由于预脉冲的存在将对靶各层等离子体辐射产生极大的影响     

激光参数影响太赫兹辐射的数值模拟

 利用2维PIC程序模拟了聚焦激光脉冲垂直入射非均匀等离子体,在界面激发超强太赫兹辐射的物理过程,研究了激光强度、脉宽和焦斑半径对太赫兹辐射功率和频率的影响,并和模式转换理论作了对比。结果表明:激光强度是影响太赫兹辐射功率的主要因素;当脉宽在等离子体波长附近时,激起的静电波振幅最大,此时对应的太赫兹辐射最强;同时存在一个最优的焦斑半径,使得辐射功率最大。     

Optical tomography problems: Investigation by the methods of the radiation transport theory

The problems of the optical diagnostics of inhomogeneous layered media are numerically studied. The question of the optical clearing of media is considered. A method for determining relative refractive indices from tomographic transmission data is proposed.     

Optical methods for the generation of terahertz radiation and subterahertz acoustics of solids

Various methods to increase the efficiency of the generation of broadband terahertz radiation based on optical rectification have been analyzed. The solutions of self-consistent optical terahertz equations have been studied using the inclined front technique. The effect of symmetric and asymmetric resonant impurity centers incorporated into a crystal has been examined. Transient and asymptotic stages of generation have been considered. Attention has been focused on the evolution of the spectra of both generated terahertz and input optic signals. One- and two-frequency generation modes have been discussed. Acoustic analogs that would provide the possibility of the generation of the gigahertz acoustic supercontinuum using subterahertz elastic signals in a solid have been analyzed. The main similarities and differences between terahertz optics and subterahertz acoustics have been revealed.     

Saturation of the hanle effect by intense broad-band laser radiation

We have developed a simple extension of the theory of the Hanle effect which is valid at arbitrary intensities of the optical field which produces the alignment. The optical field is limited to producing transitions only between the two excited atomic levels considered, and the results are applicable to experiments performed with broad-band laser excitation. The theoretical results predict that the Hanle effect is broadened but remains a lorentzian function of magnetic field. Also field-dependent saturation signals having the same widths as the Hanle effect appear in the total intensity of fluorescent light from the upper and lower laser levels. At high intensities the half-width of the degree of polarization signal differs from that of the Hanle signal. The results are in good agreement with recent experimental observations.     

Frequency up-conversion of infrared laser radiation in the human retina

Experimental observation is reported of conversion in a human retina of infrared laser radiation (with a wavelength of 1.06 μm) into the visible upon scattering by a solid target. The wavelength of this visible radiation, as estimated by several independent observers, is around 0.557 μm. Frequency up-conversion is observed down to a peak power on the retina of only 150 W/cm², while, for other laser sources, this threshold is as low as 1 W/cm². It is suggested that the observed conversion is due to the second-harmonic generation in the periodic structure of the retina of a human eye. Deviation of the observed wavelength from that of the second harmonic in vacuum is ascribed to the spectral dependence of the refractive index of rhodopsin molecules within the retina.     

激光辐照对MgB2超导体电子结构的影响

研究了光辐照对MgB2超导体电子结构的影响。对MgB2超导体进行不同时间的激光照射后,利用正电子湮没技术对光照样品进行了研究,根据正电子寿命谱参数的变化情况,对光辐照后MgB2超导体样品中缺陷及电子结构的变化进行了讨论。实验表明:MgB2超导体中的平均电子浓度对激光的照射十分敏感,并随光照时间的增加而增加。     

Quick-response film photodetector of high-power laser radiation based on the optical rectification effect

The efficiency of conversion of high-power laser radiation to an electric signal based on the optical rectification effect in nanographite films is studied experimentally. The amplitude of the signal is found to significantly depend on the size of the film, as well as on the length and arrangement of measuring electrodes. The maximal sensitivity of the photodetector (above 500 mV/MW at a wavelength of 1064 nm) consisting of the film with electrodes and operating without an external power supply and add-on components is shown to be achieved when the size of the film is comparable to the laser beam diameter. The sensitivity of the photodetector is studied under the condition when a nanosecond beam from a pulsed laser scans the surface of the film in two mutually perpendicular directions. The local sensitivity increases near the free ends of the photodetector. It is shown that the nanographite detector and a similar photodetector made of a polished silicon wafer have radically different parameters.