Simple method of the birefringent media properties determination

The simple and easy methods of determining the important birefringent medium parameters have been presented. These methods allow us to measure some important quantities of the medium: the azimuth angle and the ellipticity angle of the first medium eigenvector, the phase difference introduced by the medium and intensity transmission coefficients of the two eigenwaves. The main idea of the methods described is based on the measurement of the four intensities of the linearly polarized light passed both: through the investigated medium, and through the medium and linear analyzer.     

Short optical pulse polarization dynamics in a nonlinear birefringent doped fiber

Numerical solutions are obtained of the full self-consistent system of equations for the counter, rotating polarization components of the field of a short optical pulse propagating in a nonlinear birefringent fiber and in the ensemble of the energy-level degenerate doped resonance atoms implanted in the fiber material. In every cross section of the fiber, the ellipticity of the polarized wave experiences a complex evolution in time accompanied by rapid changes of the azimuthal angle due to the interplay of the dispersion and the Kerr nonlinear self-and cross-phase modulation. The reciprocal effect of the impurities on the traveling pulse causes oscillations of the pulse envelope that can completely distort the shape of the input signal, while the resonance absorption can drive the birefringence process from the nonlinear regime back to the linear one.     

Mapping local retardance in birefringent samples using polarization sensitive optical coherence tomography

We proposed a method to extract depth-resolved local retardance in birefringent samples from conventional polarization-sensitive optical coherence tomography (PSOCT) that uses one circularly polarized incident light. Despite the wide use of such PSOCT systems in characterizing birefringent samples, the measured cumulative retardance does not represent the true cumulative retardance when optical axis varies with depth. A Jones calculus based algorithm was designed to derive the local depth-resolved retardance from conventional cumulative PSOCT results. The algorithm was tested in samples with homogeneous optical axis as well as samples with depth-dependent optical axis.     

高反射浅光栅的偏振特性研究及其在双折射滤光片中的应用

用瑞利-傅里叶(Rayleigh-Fourier)数值方法及椭偏测量,研究了高反射正弦形浅光栅的偏振特性.当正向入射条件下,光栅周期与波长之比满足某一关系时,其反射光电场的两垂直方向分量相移差大的特性,制成了一种新颖的双折射滤光片,文中给出了这种双折射滤光片的初步实验结果.     

Simulation of electrophysical properties of biological tissues by the intracavity laser spectroscopy method

A mathematic model is constructed for predicting the absorption spectrum and dispersion of a section of a biological structure consisting of epidermis, upper layer of the derma, blood, and lower layer of the derma and placed in the cavity of an optical resonator. The quantitative estimates obtained here can be used for predicting changes in the optical properties of the sample of the biological tissue under investigation associated with various biophysical and biochemical processes in this sample.     

Use of a birefringent filter for tuning a synchronously pumped optical parametric oscillator

Design considerations are presented for birefringent filters suitable for use as tuning elements in synchronously pumped optical parametric oscillators. A particular design aspect that is important, since typical gains are rather high, is the adequate suppression of subsidiary transmission maxima, in order to maximize the tuning range. Results are presented on the performance of a picosecond synchronously pumped optical parametric oscillator based on periodically poled lithium niobate with an appropriately designed four-plate birefringent filter. PACS 42.65.Yj; 42.72.Ai     

Controlling optical properties of biological tissues: II. Coherent optical methods for studying the tissue structure

Correlation and polarization properties of dynamic speckle fields formed upon scanning in vitro human sclera samples subjected to immersion agents with a focused laser beam were studied. The immersion agent diffusion into the tissue reduces the relative refractive index of structure-forming elements (collagen fibrils) with respect to the base sclera substance and thus stimulates the passage from multiple to single scattering of a probing beam. Experimental data are presented on the evolution of the autocorrelation function of intensity fluctuations and the intensity ratio between polarized and depolarized components of laser radiation passed through a sclera layer due to artificial clarification of the tissue samples analyzed. Possible applications of the developed method to the tissue structure diagnostics are discussed.     

High-resolution ultrasound-modulated optical tomography in biological tissues

We present a novel implementation of high-resolution ultrasound-modulated optical tomography that, based on optical contrast, can image several millimeters deep into soft biological tissues. A long-cavity confocal Fabry-Perot interferometer, which provides a large etendue and a short response time, was used to detect the ultrasound-modulated coherent light that traversed the scattering biological tissue. Using 15-MHz ultrasound, we imaged with high-contrast light-absorbing structures placed >3 mm below the surface of chicken breast tissue. The resolution along the axial and the lateral directions with respect to the ultrasound propagation direction was better than 70 and 120 microm, respectively. The resolution can be scaled down further by use of higher ultrasound frequencies. This technology is complementary to other imaging technologies, such as confocal microscopy and optical-coherence tomography, and has the potential for broad biomedical applications.     

The reflection and polarization properties of non-spherical aerosol particles

In this paper, we investigate the capability of multi-angle TOA reflectance and polarized reflectance for the retrieval of aerosol properties including aerosol mode (fine mode and coarse mode), aerosol shape (sphere and non-spherical), and aerosol optical thickness. Single-scattering parameters and phase-matrix elements were computed for randomly oriented non-spherical aerosol particles. Sensitivity indices were introduced to quantify the sensitivity of the TOA total reflectance and polarized reflectance to aerosol parameters. Finally, on the basis of the sensitivity study, this paper presents a conceptual approach toward the remote sensing of non-spherical aerosol three parameters (aerosol mode, aerosol shape, and aerosol optical thickness) using the TOA total reflectance and TOA polarized reflectance for the 0.865 μm spectral bands measured at multiple viewing angles.     

Optical-frequency dependent modal birefringence and polarization mode dispersion of birefringent single-mode optical fibers over a broadband optical wavelength range

Optical-frequency dependent polarization mode dispersion as well as modal birefringence of three kinds of specially designed hollow-induced birefringent single-mode fiber are measured over an optical frequency range between 345 and 410 THz by optical frequency-domain interferometry.     

Determination of optical properties of tissues

Recent results and used way of tissue optical properties measurements in vitro with laser goniophotometer are presented. The optical properties were obtained on the basis of an indirect technique using solution of the radiative transfer equation, which relate the optical parameters of tissue with the measured parameters of reflected and transmitted radiation. The angular patterns of reflected and transmitted radiation by optically thick saline-soaked samples of tumor tissue, namely, mammary fibroadenoma, were measured at the wavelength of 0.63 μm, and the measurement data were inverted to find the absorption and extinction coefficients and the parameters of the phase function of these tumor samples. Obtained values of the optical parameters have been found to be of the same order of magnitude as the earlier reported data for similar tumor samples.     

Laser probing of biological tissues and the polarization selection of their images

Problems of increasing the signal-to-noise ratio in coherent images obtained in laser polarization probing of optically anisotropic architectonics of the morphological structure of biological tissues are discussed. Possibilities of polarization selection and contrast enhancement of such images screened by other biological tissues are analyzed.     

Azimuth-invariant mueller-matrix differentiation of the optical anisotropy of biological tissues

A Mueller-matrix model is proposed for analysis of the optical anisotropy of protein networks of optically thin nondepolarizing layers of biological tissues with allowance for birefringence and dichroism. The model is used to construct algorithms for reconstruction of coordinate distributions of phase shifts and coefficient of linear dichroism. Objective criteria for differentiation of benign and malignant tissues of female genitals are formulated in the framework of the statistical analysis of such distributions. Approaches of evidence-based medicine are used to determine the working characteristics (sensitivity, specificity, and accuracy) of the Mueller-matrix method for the reconstruction of the parameters of optical anisotropy and show its efficiency in the differentiation of benign and malignant tumors.     

Terahertz time-domain attenuated total reflection spectroscopy in water and biological solution

We demonstrate time-domain attenuated total reflection spectroscopy in terahertz frequency region. Geometry of the reflection measurement is well optimized to obtain accurate optical constants of water or aqueous biomolecular system. We determine the dielectric constants of distilled water and sucrose solutions with this technique. This technique will open new aspects in the research field of biological systems in water.     

Surface reflection properties of heavy ion optical potentials

The reflection coefficients for various heavy ion potentials are calculated in an approximation which includes a wave mechanical surface reflection term in addition to the semiclassical WKB-term. For potentials which are deep and strongly absorbing in the interior of the potential well reflection from the surface gives the dominant contribution to the reflection coefficients with small angular momenta. For shallow potentials these two terms are still not sufficient for the calculation of the reflection coefficients, indicating that higher order reflections are important.     

Ionic diffusion and space charge polarization in structural characterization of biological tissues

In this study, a new approach to the analysis of the low-frequency (1-10⁷ Hz) dielectric spectra of biological tissue, has been described. The experimental results are interpreted in terms of ionic diffusion and space charge polarization according to Sawadas theory. The new presentation of dielectric spectra, i.e. ( has been used. This method results in peaks which are narrower and better resolved than both the measured loss peaks and an alternative loss quantity . The presented method and Sawadas expression have been applied to the analysis of changes in the spatial molecular structure of a collagen fibril network in pericardium tissue exposed to glutaraldehyde (GA), with respect to the native tissue. The diffusion coefficient of ions was estimated on the basis of a dielectric dispersion measurement for an aqueous NaCl solution with a well-calibrated distance between the electrodes. The fitting procedure of a theoretical function to the experimental data allowed us to determine three diffusive relaxation regions with three structural distance parameters , describing the spatial arrangement of collagen fibrils in pericardium tissue. It has been found that a significant decrease in the structural distance from 87 nm to 45 nm may correspond to a reduction in the interfibrillar distance within GA cross-linked tissue.Received: 3 November 2003, Published online: 22 June 2004PACS: 77.22.-d Dielectric properties of solids and liquids - 87.14.-g Biomolecules: types     

Quantum properties of optical images in coupled nondegenerate parametric processes

Quantum properties of parametric amplification and frequency conversion of an optical image in coupled parametric interactions are analyzed for the case of a remote object. The coupled-wave interaction consists of a traditional process of parametric amplification in the high-frequency pump field accompanied by the frequency mixing of generated and pump waves. The photon number density and signal-to-noise ratio at the interacting frequencies are studied in the image plane at the output of the nonlinear frequency converter in the fixed pump field approximation. The degree of entanglement of optical images at frequencies above and below the pump frequency is investigated.