Search

We experimentally demonstrate the highest spectral brightness for the pulsed fiber lasers to the best of our knowledge in a compact high power and pulse energy laser system consisting of a DFB laser diode as a master oscillator and a high-power fiber amplifier based on a double-clad active tapered fiber (T-DCF). Due to the unique properties of T-DCF, this system provides more than 1 MW of peak power and pulse energy of more than 60 μJ at a frequency of 500 kHz while maintaining a spectral width of less than 0.1 nm. The spectrum broadening limits the further power scaling of the laser system. The system is capable of delivering up to 150 W average power at 10 MHz pulse repetition rate with 0.14 nm linewidth. We also demonstrate the second harmonic generation of 532 nm with over 30 W at 10 MHz repetition rate and 14.5 W at 500 kHz. The experimental results reveals that the narrow linewidth system based on a DFB laser diode and a T-DCF amplifier is an excellent and robust solution for material processing and Raman spectroscopy. acceptedVersion

A new fibre optic sensor suitable for high voltage measurements is introduced. The sensor is based on a double pass configuration of light through a Bi12TiO20 (BTO) photorefractive crystal. To obtain the double pass configuration, a back-reflecting prism with high stability to temperature variations is incorporated in the sensor head. The prism enhances the performance of the sensor allowing the BTO to work in a wide linear region of its transfer function. To prove the feasibility of our fibre optic sensor, one ac periodic wave and transient event of high voltage were measured and reported. The sensor is proved to be robust, linear, and shows high resolution in the detection of voltage impulses.

The method of IR spectroscopy for a quantitative evaluation of a structure anisotropy of metastable organic polycrystalline films is offered. In the method the division of an inverse problem of complex optical parameters determination into a number of stages with optimization on no more than two unknown parameters is used. It provides a capability of graphic support of optimization process and, as a result, minimization an error and operating correction of a possible ambiguity at each stage of the inverse problem solution. It is shown that for polycrystalline films the degree of crystallites orientation f is determined by ratio of their anisotropy. Its relation to the common used degree of crystallites orientation, which can be introduced properly only in a case of weakly absorbing films, is considered. The described method is used for investigation of optical and structural parameters of anisotropic polycrystalline copper phthalocyanine films of α-form in bands of a weak absorption (nonplanar molecular oscillations and plane skeleton deformation oscillations at about 769 cm -1 and 754 cm -1 , respectively).

Long-lived transient gratings excited by UV laser radiation in the absorption band of synthetic diamond crystals have been observed for the first time. Decay constants of the gratings depend on the crystal defects nature and lie in the range of 0.1-100 ms that is 103-104 larger than that of thermal gratings. They are observed as slow tails of the scans which describe the time evolution of the signal diffracted by the laser induced grating in the crystal. Electron-paramagnetic- resonance shows a correlation between the EPR signal and long-lived grating amplitude. The defects with unpaired electrons are mainly responsible for the gratings observed. Selectivity of the long-lived gratings to the wavelength of excitation is shown. The gratings reveal a strong sensitivity to the crystal temperature. For example, the grating lifetime decreases by several orders of magnitude when the crystal temperature increases from 20 degree(s)C to 200 degree(s)C. It proves the defect nature of the gratings observed. Light-induced grating approach appears to be a sensitive tool for the investigation of defects in diamond crystals including those that do not yield the luminescence.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We report on a fiber optic voltage sensor with optically controlled sensitivity. The sensor operates at two widely separated wavelengths (633 nm and 976 nm). one of which is a control signal (976 nm). We have demonstrated experinientally the variation of the sensor's sensitivity from 0.0 1 % to 0 per I Vnns for control power changes in the range of 0 ÷ 7 μW.

Time evolution of the intensity of light diffracted by phase grating which is induced by thermal dynamic grating (TDG) in liquid film between glass or quartz substrates is studied theoretically and experimentally. Due to heat exchange at the film boundaries the thermal gratings are also formed in substrates. The diffraction intensity of substrates can be less or comparable to that of film (non-active and active substrates, respectively). The experimental results are in a good agreement with the theoretical calculations carried out for the case when the film thickness is less the TDG period. It is shown the essential influence of the film thickness and the active-substrates contribution on the evolution of the intensity of diffracted light.

Absolute reflectivity measurements are needed for the determination of optical parameters and the thickness of a film onan absorbing substrate by method of envelopes. In the article the ratio of minima and maxima envelopes of the reflectancespectra is introduced. This parameter allows to avoid absolute measurements. An application of the ratio measurements for theanalysis of isotropic absorbing homogeneous films is described. Provided the film is transparentthe approach proposed leadsto the simple analytical solution of an inverse problem.Keywords: thin films. reflectance spectra envelopes, optical constants. 1. iNTRODUCTION Usually the optical properties of thin films and their thickiiess are calculated using ellipsornetric' or spectrophotometric2measurements. The last ones are widely used for investigation of thin films, which thickness is compared with or more thanthe wavelengths of the spectral region of an interest. Thin films are usually prepared on much thicker substrate and cannotexist free of them. Different techniques have been proposed to extract the optical parameters and the thickiless of the film on asubstrate from spectrophotometric measurements310. The transmittance or combined transmittance-reflectance measurementsare used more frequently due to their higher stability to the measurement errors and of the uniqueness of the inverse problemsolution8'9. These approaches fall down in the case of opaque or strongly absorbing substrates. To calculate uniquely therefractive index and the thickness of a thin film from reflectance measurements only one needs the reflectances both for s andp polarizations1' . Curve-fluing

The method of envelopes and based on reflectance measurements only, is developed for investigation of UniaXia! absorbingfilms formed on absorbing substrates. Two optical axis orientations parallel and perpendicular to the film interfaces areanalyzed. Reflectance spectra for p and slinear polarizations are used to determine the complex dielectric constants of thefilm & (2) and (2) and its thickness. For the transparent films the analytical solutions are obtained for these parameters. Thesimple iterative procedure are used for their determination in the case of absorbing films. Numerical model calculations arecarried out to study the characteristics of the method developed. They show high stability of the real parts of and h determination to the measurement error.Keywords: reflectance spectra, method of envelopes, uniaxial absorbing films, optical constants. 1.INTRODUCTION Although thin films have been widely used in optical applications for many years, the problem of its optical

Peculiarities of thermal dynamic gratings application for heat transfer study of solids are investigated both theoretically and experimentally. Techniques are proposed for the reduction of influence of thermal grating aperture limitation and scattered coherent background on accuracy of measurements. A thermal excitation of transparent samples with absorbing film of liquid in contact is considered.

It is shown that the air-film material reflectance coefficient, and that for the film material- substrate, can be restored from envelopes of the interference pattern in reflectance spectra. Doing so for oblique incidence of light and for two of its polarizations, optical parameters of an absorbing film may be determined without any film dispersion assumptions. Film thickness h is calculated then analytically. Knowing h, the film absorption coefficient can be obtained with high accuracy. Numerical calculations are given to illustrate the method application.

An approach of ellipsometric measurements both from ambient media and from transparent or weakly absorbing substrate has been proposed to determine optical constants and thickness of anisotropic films. According to this approach the main refractive indices are calculated by an iterative procedure while an optimization is used to average the values obtained over the parameters measured at one or several incidence angles. The approach proposed has been used for a determination of optical constants and thickness of multimolecular Langmuir-Blodgett films based on the derivative of 5-[4-(stearoylamino)phenyl] isophthtalic acid.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The genes encoding esterase D (ESD) and α2-macroglobulin (A2M) were mapped using 3H-labeled cDNAs to sheep chromosome 3p26→p24 and 3q26→q35 respectively.

We determined the sequence of Tu80, one of the molecular clones derived from microdissected fragments of Chromosome (Chr) 17. The sequence data demonstrated that Tu80 contains an open reading frame (ORF) of 204 bp. Two sequences within the ORF, one homologous to the LINE1 element and the other to the first intron of the C epsilon gene of mouse immunoglobulin, were observed. A separate sequence, homologous to Tu80, designated as NOV1, was isolated from a genomic library of mouse Chr 17. NOV1 was found to contain an inserted B2 repeat, making it structurally different from Tu80. The sequences of Tu80 and NOV1 were compared with those of LINE1 and the first intron of the C epsilon gene. The results suggest that the ancestor of the Tu80-like sequence might have arisen through recombination between a LINE1 element and the C epsilon gene. It is concluded that Tu80 and NOV1 might have resulted from duplication of an ancestral sequence followed by divergence. The comparative analysis also demonstrated a high degree of conservation of the LINE1-like sequence in Tu80 and NOV1. Based on the structure of human, rat, rabbit, and mouse LINE1 fragments, as well as those of NOV1 and Tu80, a phylogenetic tree was constructed. The available data tend to support the assumption that the ancestor for the Tu80-like sequence might have arisen not later than 27-33 million years ago.

The gene for esterase D (ESD) has been localized to chromosomes in a number of mammals by somatic cell hybrid analysis. Regional localization of this gene by in situ hybridization has been performed only in the human 13q14.1-q14.2 (Human Gene Mapping 10 1989). Attempts to obtain panels of hybrid cells in the pig have been unsuccessful. Therefore, the basic ap- proach to chromosome mapping in the pig must be in situ hybridization. Here we describe the localization of the pig ESD gene to position 13q3.4--->q4.4. In the 145 metaphases analyzed in the present study, 112 of the 423 total grains (26%) were present on Chromosome (Chr) 13 (Figs. 1 and 2). Of these, 70 (62.5%) were clustered at 13q3.4-->q4.4. Chr 13 repre- sents 8.2% of the total length of the haploid set. As- signment of the ESD gene to this chromosome is there

Reviewed are the approaches for the determination of the optical constants - refraction indices, absorption coefficients and thickness of thin uniaxial film with various optical axis orientations, arbitrary among them. The comparative analysis of various measurements - MAI (multi angle of incidence ellipsometry), MTE (multi film thickness ellipsometry), IHE (multi immersion ellipsometry) and MOE (multi orientation ellipsometry) and corresponding techniques for solving the inverse task is given for each type of optical axis orientation.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.