Secondary extinction (SE) is inherently related to the pole density, P. The latter represents a crystalline volume fraction normalised to random distribution that contributes to reflection. In fact, any measured point inside the reflection range 2 Delta theta is affected to a different extent by the SE due to variation of both pole density and energy distribution of the incident beam intensity, I-0. However, to evaluate a SE effect of the reflection as a whole, its integral intensity must account for pole density, (P) over bar, being dependent on integral breadth of reflection. Thus, the aim of the present study is to develop a technique for calculating the integral breadth of reflection using extinction free data of both its integral intensity and maximal intensity. The reformed data can be used for sensitive treatment of the SE effect in textures and powders including nanoscale materials as well.

Security measures sometimes require persistent surveillance of government, military and public areas Borders, bridges, sport arenas, airports and others are often surveilled with low-cost cameras. Their low-light performance can be enhanced with laser illuminators; however various operational scenarios may require a low-intensity laser illumination with the object-scattered light intensity lower than the sensitivity of the Ladar image detector.This paper discusses a novel type of high-gain optical image amplifier. The approach enables time-synchronization of the incoming and amplifying signals with accuracy <= 1 ns. The technique allows the incoming signal to be amplified without the need to match the input spectrum to the cavity modes. Instead, the incoming signal is accepted within the spectral band of the amplifier. We have gauged experimentally the performance of the amplifier with a 40 dB gain and an angle of view 20 mrad.

This paper discusses an advanced target in the loop (ATIL) system with its performance based on a nonlinear phase conjugation scheme that performs rapid adjustment of the laser beam wavefront to mitigate effects associated with atmospheric turbulence along the propagation path. The ATIL method allows positional control of the laser spot (the beacon) on a remote imaged-resolved target. The size of this beacon is governed by the reciprocity of two counterpropagating beams (one towards the target and another scattered by the target) and the fidelity of the phase conjugation scheme. In this presentation we will present the results of the thorough analysis of ATIL operation, factors that affect its performance, its focusing efficiency and the comparison of laboratory experimental validation and computer simulation results.

To gain accuracy and, hence, physical reality of the data acquired by XRD measurements of fibre textures, a technique is elaborated to achieve experimental values, which are free of extinction effects. Its elaboration is based on combining basic definitions of the extinction theory and texture analysis. This technique is applicable to characterization of metal coatings that appear infinitely thick for X-rays. A nickel sample representing <100> + <221> texture components is used as a model. Resultant derived series of data on pole-density distribution of the {200} diffraction pole figure shows that the data corresponding to the main <100> texture component are strongly affected by extinction. On the contrary, due to definitions that require reduction of the intensity distribution to multiples of random density, the extinction-free values of the volume fraction of texture components do not differ substantially from those calculated by standard methods. Evidently, any of the standard methods for volume fraction measurements provides reasonable data if secondary extinction is even disregarded.

Shortly after the construction and operation of the first optical laser, designs for hard x-ray (that is, >10keV) laser systems were proposed.1, 2 Since that time, scientists have endeavored to build such a device3–7 because of the wide application that the collimated (i.e., with parallel light rays), coherent beam of femtosecond keV x-ray pulses will find in science, technology, and medicine. For instance, such an instrument could be used for tumor radiotherapy without damaging surrounding tissue. A laser consists of two main components: the resonator and the amplifying (or ‘gain’) medium. The resonator is a system of mirrors that can set up standing waves for the desired frequency of light, and the gain medium amplifies the light that passes through it. There are several severe problems to be solved for both components when building a keV x-ray laser. Atoms emit x-ray radiation when electrons move from a higher to a lower electron shell, and one restriction is the femtosecond lifetime of inner-core electron states. Another is the very low reflectivity of available ‘mirrors,’ which are carefully chosen crystals. In addition, the reflecting crystals’ Bragg angle must match exactly with the x-ray laser line wavelength. Atomic inner-shell ionization pumped by very short electron or x-ray pulses has been proposed2 as a possible means for achieving gain, and, in fact, gain at 1.146nm has been obtained by pumping neon gas with x-ray pulses.7 We designed and built the first keV x-ray laser resonator composed of four highly oriented pyrolytic graphite (HOPG) crystals (see Figure 1).8 For a complete round trip, a Bragg diffraction angle B of 45 ◦ is necessary (that is, the angle between the direction of the incident beam and the resulting diffracted beam). The graphite lattice spacing, d, is 1.677Å. Reflection from the crystal plane is denoted by the Miller index (004) has B D 45 at 2.37Å, which coincides with the wavelength of the neodymium x-ray emission line denoted L ̨ . Another possibility for resonator crystals is diamond crystals,9 which have much higher reflectivity than graphite. However, the Bragg diffraction acceptance angle is very narrow (of the order of arcseconds for diamond crystals), Figure 1. Schematic representation of path traversed by the x-ray beams for two wavelengths in a four-crystal laser resonator. Dashed line: path taken by the neodymium ‘L ̨ ’ (5.27keV) x-ray photons making complete round-trips in the resonator. Solid line: path taken by the chromium ‘K ̨ ’ (5.41keV) x-ray photons and of the x-ray photon beam used to measure the reflectivity, losses, and change in divergence as it propagates in the cavity. G1, G2, G3, and G4 designate the location of the highly oriented pyrolytic graphite (HOPG) crystals. Reprinted with permission.8

We have designed, constructed, and tested an x-ray laser resonator operating in the hard x-ray, keV energy region. This ring x-ray laser cavity is formed by four highly oriented pyrolytic graphite crystals. The crystals are set at the Bragg angles that allow for the complete 360 degrees round trip of the 2.37 angstrom, 5.23 keV L-alpha line of neodymium. In addition, we also present experimental data of a similar ring laser resonator that utilizes the Cr K-alpha, 5.41 keV, x-ray line to propagate through the four mirrors of the cavity. The specific properties of these x-ray laser resonator mirrors, including reflection losses and cavity arrangement, are presented. (C) 2013 AIP Publishing LLC [http://dx.doi.org/10.1063/1.4803071]

Sessions C670In our previous studies of binding properties and conformational adaptability of a known nitrate/sulfate receptor N,N'-3-azapentane-1,5-bis[3-(1-aminoethylidene)-6-methyl-3H-pyran-2,4-dione] (L) [4] toward various charge-dispersed monoanions (HSO 3 -, ClO 4 -, IO 4 -, PF 6-and SbF 6 -) we have shown that L is able to discriminate anions on the basis of their charge density.Herein we present two structures whit the same anion, SCN -, achieves two different complexes with L, thus displaying versatile binding nature of this podand.Geometry and (hydrogen-bonding) acceptor properties of SCN -allow two distinct binding modes.When anion uses a sulfur atom as an acceptor, all strong hydrogen bond donors of the podand become coordinatively saturated by interactions with the oxo-functionalities from neighboring podands, so the only weaker C-H groups are accessible for anion binding.On the other hand, when anion uses nitrogen atom as a hydrogen-bonding acceptor then podand uses its N-H groups to accomplish optimal binding.

Pole density is a fundamental parameter of the diffraction pole figures used for calculation of orientation distribution functions that characterize the physical properties of textures. To gain accuracy and, hence, physical reality of the data, an approach is elaborated to derive experimental pole-density values, which are free of extinction effects. The approach is based on the intrinsic invariability of the empirical extinction coefficient k at a series of levels of interaction of the diffraction process. The invariability of k is a precondition for nullifying the extinction effects by equating couple of its expressions defined with the intensities measured at the same series of the levels of interaction. A nickel sample representing < 100 > texture component is investigated. The resultant derived series of data for the distribution of pole density P of the {200} diffraction pole figure is in exact accord with kinematic theory.

This paper describes work that demonstrated the feasibility of producing a gated digital holography system that is capable of producing high-resolution images of three-dimensional particle and structure details deep within dense particle fields of a spray. We developed a gated picosecond digital holocamera, using optical Kerr cell gating, to demonstrate features of gated digital holography that make it an exceptional candidate for this application. The Kerr cell gate shuttered the camera after the initial burst of ballistic and snake photons had been recorded, suppressing longer path, multiple scattered illumination. By starting with a CW laser without gating and then incorporating a picosecond laser and an optical Kerr gate, we were able to assess the imaging quality of the gated holograms, and determine improvement gained by gating. We produced high quality images of 50–200 μm diameter particles, hairs and USAF resolution charts from digital holograms recorded through turbid media where more than 98% of the light was scattered from the field. The system can gate pulses as short as 3 mm in pathlength (10 ps), enabling image-improving features of the system. The experiments lead us to the conclusion that this method has an excellent capability as a diagnostics tool in dense spray combustion research.

straightforward approach is devised for XRD characterizations of textures by nullifying the extinction effect. To this end, a proper reconsideration of the nature of the extinction coefficients is carried out. It is shown that whereas the SE coefficient g is proportional to the product of pole density P and incident-beam intensity I 0 , the empirical extinction coefficient k is independent of the ratio g/PI 0 . Based on the invariability of the k-coefficient with respect to g/PI 0 , the extinction effect is nullified by equating two its expressions defined by intensities of a reflection measured at a series a levels interaction whose variation is controlled by P and I 0 . Techniques representing extended versions of this approach are developed for (i) reliability-evaluation of the controlled variation of the levels of interaction by using instrumental variable (generator current) and, hence, to test the capability of the XRD apparatus to collect accurate and precise data, and (ii) determination of extinction-free data of the pole density that is a fundamental physical parameter. The experimental results are discussed in terms of the influence of extinction coefficient g on the accuracy in the determination of the pole density in ideal direction of nickel texture.

We report a photonic crystal fiber (PCF) coupler having an ultrawide spectral bandwidth keeping single mode operation. The use of the PCF coupler in a fiber-based optical coherence tomography (OCT) system enables us to handle the wide spectral bands of various light sources, including superluminescent diodes (SLDs) at 1300 nm and 820 nm, Ti:sapphire lasers, and white-light sources. The multiband imaging performances of the PCF-based OCT system are demonstrated by obtaining dental images at 1300 nm and 820 nm with the same setup. In addition, we show that the PCF coupler could cover the spectrum over a one octave span and guide both the fundamental wave (1030 nm) and the second harmonic wave (515 nm) simultaneously.

In this paper we report the results of the analysis and experimental modeling of the target-in-the-loop (TIL) approach that is used to form a localized beacon for a laser beam propagating through turbulent atmosphere. The analogy between the TIL system and the laser cavity has been used here to simulate the process shaping the laser beacon on a remote image-resolved target with rough surface. The TIL breadboard was integrated and used for laboratory modeling of the proposed approach. This breadboard allowed to simulate the TIL arrangement with a rough-surface target and laser beam propagation through the turbulent atmospheric layer. Here we present the initial results of the performed studies.

for obtaining ten times higher intensity than that of the ordinary-type single crystal analyzer with equal resolution.Experimental details and applications to structure analysis such as Rietveld refinement will be reported.

We present multiphoton imaging based on semiconductor planar waveguide technology which can be used as a transmitter and receiver simultaneously. In particular, silicon on insulator waveguides with p-i-n diode structures are used to demonstrate <5 μm resolution three-photon imaging of Er3+:Y2O3 microparticles by using 1550 nm excitation. Additional theoretical study has been performed to demonstrate the proposed scheme for three-dimensional tomography of micron-sized objects, which could be realized by using multiple transmitter-detector pairs.

We present multiphoton microendoscopy with a rotational probe and a 1 microm fiber-based femtosecond laser. The rotational probe is based on a double-clad photonic crystal fiber, a gradient index lens, a microprism, and a rotational microelectronicmechanical system (MEMS) motor. The MEMS motor has a diameter of 2.2 mm and can provide 360 degrees full-view rotation. The fiber laser provides ultrashort pulses with a central wavelength at 1.034 microm and a repetition rate of 50 MHz. Second-harmonic-generation images of rat-tail tendon and fish scale are demonstrated with the rotational probe-based multiphoton system.

We present a kind of rotational two photon mciroendoscopy for 1 mu m fiber femtosecond laser. The fiber laser provide ultrashort femto-second pulses with center wavelength at 1.034 mu m and repetition rate of 50MH. The rotational probe is based on double cladding photonic crystal fiber (CD PCF) fiber, Grin lens, microprism and rotational MEMS motor. The MEMS motor has diameter of 2.2mm and can provide 360 degree full view rotation. We experimentally show that the DC PCF fiber works for 1 mu m fiber laser two photon system. Second harmonic generation (SHG) singnal line profile of rat tail tendon and fish scale was taken with the endoscopy system.

We show that silicon waveguides can simultaneously be utilized as focusing device and also as detectors in nonlinear fluorescence imaging. Detection and imaging of Lt20mum erbium particles by using 1550 nm excitation are demonstrated experimentally.

The photoredox reaction of trisoxalato cobaltate (III) has been studied by means of ultrafast extended x-ray absorption fine structure and optical transient spectroscopy after excitation in the charge-transfer band with 267-nm femtosecond pulses. The Co–O transient bond length changes and the optical spectra and kinetics have been measured and compared with those of ferrioxalate. Data presented here strongly suggest that both of these metal oxalato complexes operate under similar photoredox reaction mechanisms where the primary reaction involves the dissociation of a metal–oxygen bond. These results also indicate that excitation in the charge-transfer band is not a sufficient condition for the intramolecular electron transfer to be the dominant photochemistry reaction mechanism.

Using first-order approximation of secondary extinction (SE) correction, a method is described for conversion of extinction-affected reflection profile into kinematical (extinction-free) one. In this connection, changes of the two reflection profile parameters integral breadth and FWHM are investigated by means of change of the level of interaction between X-rays and crystal medium. To this end, a controlled reduction of the incident-beam intensity is carried out by means of the transmission factor of a foil crossed by the incident beam. The investigation is confined to 111 and 222 reflections corresponding to the ideal < 111 > direction of the main texture component of electrodeposited silver coating appearing infinitely thick to the X-rays. It is found that the extinction-induced reflection broadening is controlled by the reflectivity Q, texture factor P and incident-beam intensity I(0).