Photon number measurement using heterodyne method for a detector's quantum efficiency determination based on spontaneous parametric down-conversion.

Active development of quantum informational components such as quantum computers and quantum key distribution systems requires parameter characterization of single photon detectors. A key property of the single photon detectors is detection efficiency. One of the methods of the detection efficiency measurement, as listed in the international standard ETSI, is the reference-free twin-photon-based Klyshko method. The signal-to-noise ratio (SNR) of this method depends on the combination of the pump wavelength, the nonlinear crystal's axis angle, and the type of detector's sensitive element. When the combination is difficult, one has to deal with the low SNR of the detector counts measurement. To gain the high SNR, one has to average the long record complicated with the "random telegraph signal" noise. This type of noise exhibits high spectral density at a zero frequency, where simple averaging works. The heterodyne based method we have proposed is to perform averaging at the higher frequency of the modulation introduced to the standard Klyshko measurement scheme. The method was numerically simulated and experimentally tested. The 14 times improvement in SNR for the proposed method relative to the simple averaging was demonstrated by the numerical simulation and confirmed experimentally.

Laser interference microscopy of amphibian erythrocytes: impact of cell volume and refractive index.

This study examined the action of anisosmotic media on the volume of nucleated erythrocytes isolated from Rana temporaria. Elevation of medium osmolarity from 100 to 345 mOsm resulted in attenuation of mean cell volume by more than 3-fold, estimated by hematocrit measurement. By contrast to this 'classic' erythrocyte volume evaluation technique, we did not observe any significant cell volume modulation by examining the 3D reconstruction of erythrocyte interference images obtained by laser interference microscopy. Comparative analysis of mean cell volume, phase height and cell area appraised by laser interference microscopy showed that the lack of visible alterations of phase image geometry was caused by sharp elevation of the average refractive index of the cytoplasm in shrunken cells. Thus, our results show for the first time that laser interference microscopy in combination with a direct method for cell volume measurement may be employed for estimation of the refractory index of intracellular milieu and for assessment of changes of physical chemical properties of the cytoplasm evoked by diverse stimuli including osmotic stress.

[New possibilities of studying microbial objects by laser interference microscopy].

A novel method, laser interference microscopy, has been developed for studying the morphofunctional state of bacterial cells and the structure of bacterial communities. The following potentialities of the method are shown: rapid determination of the cell structure and subcellular structures (nucleus zone, vacuoles, lamellar structures) and the physiological state of the cell, as well as the study of the structure of bacterial communities (biofilm). The method does not require any additional preparation of cells before the investigation (fixation, staining, treatment with contrasting substances), which reduces the possible appearance of artifacts to a minimum and enables one to use laser interference microscopy for in vivo investigations.

[The use of nanoparticles for the study of conformations submembrane hemoglobin].

The advantages and features of the integrated application of methods of atomic force microscopy, laser interference microscopy and Raman microscopy in the study of erythrocytes was discussed. For the successful application of Raman microscopy in surface enhanced Raman spectroscopy mode the silver colloids was using. The dependence of the enhancement of Raman signals from silver colloids size was demonstrated. The using of developed methods for clinic diagnostic was discussed.

Evaluation of erythrocyte shape and status by laser interference microscopy.

The area, thickness, and volume of erythrocytes of different types (discocytes, stomatocytes, and echinocytes) from normal subjects and coronary patients were studied by laser interference microscopy. Increase of pH value leading to the stomatocyte-discocyte-echinocyte transformations resulted in a slight decrease of cell volume. In coronary patients, erythrocyte had larger area and volume and exhibited increased aggregation capacity compared to erythrocytes from controls. The results recommend laser interference microscopy as an adequate method for erythrocyte evaluation in laboratory diagnostic measurements.

[Coherent oscillations of the molecular state of protein in live cells].

The paper describes results of experimental studies of changes in the refractive index of the live cell (human erythrocyte) substance. The measurements were carried out using automated interference microscope. Oscillations of the refractive index were detected with the amplitude 5-10% and period 1 x 10(3)-3 x 10(3). In other words, oscillations with a near one hour period is equal to 10-45 min. It is supposed that these oscillations may result from coherent changes in the state of protein molecules.

[Optic methods for measurements of muscle fiber birefringence]. / Opticheskie metody izmereniia dvulucheprelomleniia myshechnykh volokon.

An optical method for measuring the birefringence of muscle fibers was developed, which is realized on an automated Linnick interferometer microscope equipped with a laser. It was shown that the method has some advantages over the methods based on measurements of the intensity of light passing through a crossed polarizer, an analyzer, and a fiber (light polarized microscopy). The method involves direct phase measurements of optical path length at the parallel and perpendicular orientations of the polarization plane of probing radiation. The phase image is reconstructed automatically from interferograms with the use of the four-frame phase-shifting algorithm. The phase images of one and the same central part of the fiber at different orientations of the polarization plane represent two-dimensional numerical maps of the optical path length. The subtraction of these images gives a two-dimensional map of the phase shift, which includes information about the birefringence of the fiber. A formula for birefringence measurements was deduced, which has a certain advantage in comparison to that used earlier in that it does not take into account the thickness of a fiber that depends on the measurement point. The birefringence is normalized to a value of the half sum of phases, which are measured separately in the course of the experiment.

[Two-dimensional reconstruction of birefringence map of the skeletal muscle sarcomere in relaxed and rigor states studied by interference microscopy]. / Dvumernaia rekonstruktsiia karty dvulucheprelomleniia sarcomera skeletnoi myshtsy v relaksirovannom i rigornom sostoianii po dannym interferentsionnoi mikroskopii.

A new method of automatized quantitative interferometry of skeletal muscle fibers was developed for the investigation of birefringence. A device based on the Linnic microscope was constructed to obtain phase images, which are two-dimensional pictures of birefringence. For the first time, two-and-three-dimensional maps of both total birefringence and birefringence for individual sarcomeres in the central part of muscle fiber were visualized using large databases. It was shown that total birefringence of fibers at rest length in the rigor state was lower as compared with the relaxed. Birefringence values from individual sarcomere interferograms revealed also that normalized A-disk birefringence was lower in the rigor state. The results obtained could be explained by a decrease of thick filaments anisotropy, due to the moving away of myosin heads from the rod during transition into the rigor state.

[The use of a modelling method in craniometry]. / Ispol'zovanie metoda modelirovaniia v kraniometrii.

Laser interferometry is proposed for accurate measurements of the external parameters and fixation of the relief of human skull surface. This method creates a detailed three-dimensional computer model of the object of investigation, which can be used in automated systems of personality identification based on investigation of the skull and life-time photos. Further development of the method opens new vistas in automation of the trassological and ballistic identification.

[New possibilities of optic microscopy in studies of blood cells]. / Novye vozmozhnosti opticheskoi mikroskopii pri issledovanii kletok sistemy krovi.

Modern biomedical tasks put forward new requirements to the instrumental base of microscopy. This paper outlines the prospective trends in microscopy which are the most interesting for medicine, on the one hand, and analyzes the probability of meeting the requirements of medicine by modern methods of optic electronics and computer processing of optic information. The authors analyze the following trends: microscopy of three-dimensional objects, super-resolution, microscopic measurements, and automation of microscopes. Progress in optic electronics and computer processing of images permits considering these trends as a priority task of modern microscopy.