Random object optical field diagnostics by using carbon nanoparticles.

We propose a new approach of using carbon nanoparticles for correlation optical diagnostics of а complex scalar optical field created by scattering and diffraction of radiation off a rough surface. This surface is simulated and we generate a diffraction pattern of the amplitude and phase distribution in the far field. Carbon nanoparticles of a certain size and concentration are obtained by the bottom-up methods of hydrothermal synthesis of citric acid and urea followed by centrifugation. The optical properties of carbon nanoparticles, such as luminescence and absorption in the visible spectrum that essentially differs for different wavelengths, as well as particle size of about dozen nanometers, are the determining criteria for using these particles as probes for the optical speckle field. Luminescence made it possible to register the coordinate position of carbon nanoparticles in real time. The algorithm for reconstruction of the scalar optical field intensity distribution through the analysis of the nanoparticle positions is here displayed. The skeleton of the optical speckle field is analyzed by Hilbert transform to restore the phase. Special attention is paid to the restoration of the speckle field's phase singularities.

Changing image of correlation optics: introduction.

This feature issue of Applied Optics contains a series of selected papers reflecting recent progress of correlation optics and illustrating current trends in vector singular optics, internal energy flows at light fields, optical science of materials, and new biomedical applications of lasers.

Correlation optics in progress: introduction to the feature issue.

This feature issue of Applied Optics contains a series of selected papers reflecting recent progress of correlation optics and showing, in part, the trend from micro-optics to nano-optics.

Some current trends of correlation optics metrology of coherence and polarization.

New feasibilities for metrology of coherence and polarization of light fields provided by correlation optics approaches are considered. This paper shows these approaches are fruitful in measuring the field parameters that are critical for optical diagnostics using the data on the degree of coherence and the state and the degree of polarization of partially coherent and inhomogeneously polarized fields.

Emerging correlation optics.

This feature issue of Applied Optics contains a series of selected papers reflecting the state-of-the-art of correlation optics and showing synergetics between the theoretical background and experimental techniques.

Feasibility of estimating the degree of coherence of waves at the near field.

Information on the degree of coherence of electromagnetic optical waves that is contained both in intensity modulation and in spatial polarization modulation of the resulting distribution of superposing waves is considered. Such an experimental situation is often realized in near-field optics. The possibility of experimental estimation of the degree of mutual coherence of waves polarized at the incidence plane is shown.

Polarization manifestations of correlation (intrinsic coherence) of optical fields.

The statement is substantiated that the experimental estimation of the degree of intrinsic coherence of statistical vector optical fields must include not only the measurement of the visibility of the interference pattern but also the degree of polarization in the resulting spatial distribution of a field.

Optical correlation diagnostics of rough surfaces with large surface inhomogeneities.

The feasibilities for optical correlation diagnostics of rough surfaces with large surface inhomogeneities by determining the transformations of the longitudinal coherence function of the scattered field are substantiated and implemented.

Singular-optical coloring of regularly scattered white light.

When the surface roughness is comparable with the wavelength of the probing radiation, the scattered field contains both the regular (forward-scattered) component of coherent nature and the diffusely scattered part. Coloring of the regular component of white light scattered by a colorless dielectric slab with a rough surface is considered as a peculiar effect of singular optics with zero (infinitely extended) interference fringes. To explain the observed alternation of colors with respect to the increasing depth of the surface roughness, we apply a model of transition layers associated with the surface roughness. By applying the chromascopic technique, it is shown that the modifications of the normalized spectrum of the forward-scattered white light can be interpreted as the effect of a quarter-wavelength (anti-reflecting) layer for some spectral component of a polychromatic probing beam.

Feasibilities of interferometric and chromascopic techniques in study of phase singularities.

The feasibilities of using interferometric and chromascopic techniques in the diagnostics of phase singularities and in the study of a phase structure of the field in their vicinity are demonstrated. The peculiar evolution of singularities into caustics produced by phase elements of singularity-generating objects of spherical and cylindrical shape is studied.

Complex degree of mutual polarization of biological tissue coherent images for the diagnostics of their physiological state.

This is the first attempt devoted to the 1st-4th order statistic analysis of the complex degree of mutual polarization of biological tissues coherent images. The ensemble of diagnostic criteria (skewness and kurtosis of two-dimensional distributions of complex degree of mutual polarization) of pathological changes of muscular and connective (skin derma) tissues is defined.

Role of caustics in the formation of networks of amplitude zeros for partially developed speckle fields.

The topology of a partially developed speckle field was studied by use of interference techniques through computer simulation. Amplitude and phase structures in the vicinity of caustics for a coherent radiation field scattered at a surface with large inhomogeneities were investigated. It was confirmed that the caustics are indispensible components of the procedure for the formation of networks of amplitude zeros for a coherent field scattered by a rough surface with large inhomogeneities. It is shown that the formation of interference forklets in the field gives evidence of changes in the field's topology, as these forklets are a diagnostic sign of transition from a caustic to a three-dimensional pattern of a diffraction catastrophe.

Wavelet analysis of two-dimensional birefringence images of architectonics in biotissues for diagnosing pathological changes.

A method for polarization filtering, correlation processing, and wavelet analysis of coherent images of physiologically normal and necrotically changed (myocardium infarct) muscle tissue is presented. A technique for early optical diagnosis of the appearance of these biological tissues and the course of their degenerative-dystrophic changes is proposed.

Applicability of the singular-optics concept for diagnostics of random and fractal rough surfaces.

We introduce the singular-optics approach for classification of rough surfaces with large-scale inhomogeneities into random and fractal surfaces. The maps of amplitude zeros of a field versusthe parameters of the rough surfaces and the position of the observation zone are obtained and analyzed. It is shown that the local density of amplitude zeros in the scattered field serves as an appropriate parameter with which to classify the surface of interest into a surface with a height distribution that can be described as a random or a fractal process.

Fractal description of rough surfaces.

The multifractal description of rough surfaces is discussed and the mechanisms for generation of fractal and multifractal height distributions of inhomogeneities for rough surfaces are simulated. The original technique for estimating the spectrum of singularities is proposed for the study of these distributions.

Interferometric methods in diagnostics of polarization singularities.

An interferometric technique for analysis of a polarization singular skeleton (s contours and C points) of an optical vector field is elaborated. It was shown that complete characteristics of C points and s contours may be reconstructed from interferometric data. Some examples of elaborated interferometric technique application to the analysis of randomly polarized speckle-fields singularities are presented.