Oscillatory measurements of silicone oils —Loss and storage modulus master curves

The work describes a way to obtain loss modulus and storage modulus master curves from oscillatory measurements of silicone oils.The loss modulus master curve represents the dependence of the viscous flow behavior on · ₀ ^* and the storage modulus master curve — the dependence of the elastic flow behavior on · ₀ ^* .The relation between the values of the loss modulus and storage modulus master curves (at a certain frequency) is a measurement of the viscoelastic behavior of a system. The G/G-ratio depends on · ₀ ^* which leads to a viscoelastic master curve. The viscoelastic master curve represents the relation between the elastic and viscous oscillatory flow behavior.     

Electron irradiation of ion-implanted n-type Si-SiO2 structures studied by deep-level transient spectroscopy

2 structures implanted with 50-keV boron ions is studied by deep-level transient spectroscopy (DLTS) measurements. The DLTS spectra of ion-implanted samples exhibit one peak which corresponds to a deep level located in the forbidden gap of the silicon matrix at E_c-0.40 eV below the conducting band edge. New additional shallower levels are found in the spectra following bombardment by high-energy electrons, the peak intensity being dependent on the irradiation dose. The corresponding activation energy of the created defects, the density of the traps, and the electron-capture cross sections are evaluated. Received: 27 October 1997/Accepted: 8 December 1997     

Passive harmonic mode-locking of a soliton Yb fiber laser at repetition rates to 1.5 GHz

We report passive harmonic mode locking of a soliton Yb fiber laser at repetition rates continuously scalable up to 1.5 GHz. The laser generates transform-limited 500 fs pulses, with pulse energies of 30-100 pJ. At the 31st harmonic (1.3 GHz), the cavity supermodes are suppressed by 35 dB, and the pulse-to-pulse timing jitter is 6 ps.     

Resonant optical interactions with molecules confined in photonic band-gap fibers

We investigate resonant nonlinear optical interactions and demonstrate induced transparency in acetylene molecules in a hollow-core photonic-band-gap fiber at 1.5 mum. The induced spectral transmission window is used to demonstrate slow-light effects, and we show that the observed broadening of the spectral features is due to collisions of the molecules with the inner walls of the fiber core. Our results illustrate that such fibers can be used to facilitate strong coherent light-matter interactions even when the optical response of the individual molecules is weak.     

Effect of the lattice-atom thermal vibrations on the reflection of ions from a single crystal

Computer simulation of the reflection of a keV ion beam from a single crystal is carried out for different target temperatures. Ar ions bombarding obliquely a Cu lattice with 2 keV, and a Ni crystal with 30 keV energy are considered. The potentials used are of Born-Mayer (Ae^?r/b) and Firsov (Br^?2) type respectively. Uncorrelated thermal vibrations of atoms with Gaussian distribution of their displacements are taken into account. The spatial and energy distribution of the reflected ions obtained for different temperatures are discussed. The energy spectra are compared with the experimental data for the same conditions.     

Theory of cascade tripler of optical frequency with high conversion efficiency

The regimes of high conversion efficiency of cascade triplers of optical radiation are theoretically investigated. A conversion efficiency of 100% for plane waves can be reached. Analytical expressions for the wave amplitudes in this case are given. The conversion efficiencies for a laser beam with Gaussian distribution of the amplitude in space and time are numerically computed. The maximum efficiency for such a beam is about 50%. Some experimental situations are discussed.     

Oxygen detection using yttria-stabilized zirconia thin films doped with platinum

Yttria stabilized zirconia (YSZ) thin films are obtained using both spray-pyrolysis and dip-coating. The ability of YSZ films incorporated with platinum nanospecies (Pt-YSZ) to detect oxygen is compared with that of pure YSZ thin films using a new experimental setup. With this system, the surface electrical resistance of the films as a function the oxygen content is measured at a fixed temperature. In addition, the effects of thermal annealing on the oxygen sensitivity of the films are observed. Platinum doped samples, Pt-YSZ, show different kinetics of carrier diffusion as compared to pure YSZ samples.     

Subvarieties of the matrix variety of second order

LetR _s be the subalgebra ofM ₂(K[t]/(t ^s )) generated bye ₁₁,e ₂₂,te ₁₂ andte ₂₁, whereK is a field of characteristic 0,K[t] is the polynomial algebra in one variablet and (t ^s ) is the principal ideal inK[t], generated byt ^s . The main result of this paper is that we have described theT-idealT(R _s ). Besides the two matrix polynomial identities — the standart identityS ₄ and the identity of Hall, thisT-ideal is generated by one more explicitly given identity. The algebrasR _s are interesting due to the fact that the proper identities of any subvarietyu of the variety ℳ=varM ₂(K), generated by the matrix algebraM ₂(K) of second order overK, asymptoticaly coincide with the proper identities of someR _s . Partially supported by Grant MM605/96 of the Bulgarian Foundation for Scientific Research.     

Multifocal multiphoton endoscope

We report a miniaturized resonant/non-resonant multi-fiber raster scanner that is paired with a gradient-index lens assembly to achieve a compact and flexible multifocal multiphoton endoscope capable of longitudinal parallel image acquisition. Multiphoton images are obtained simultaneously at three axial depths, separated by ≥4.8 μm, by incorporating three axially offset double clad optical fibers into the miniaturized scanner. The fabricated endoscope has an outer diameter of 3 mm, a rigid length of 4 cm, and acquires images at 4 frames/s per focal plane, with lateral and axial resolutions for two-photon imaging of 0.8 and 10 μm, respectively.     

Electron beam emission from a diamond-amplifier cathode

The diamond amplifier (DA) is a new device for generating high-current, high-brightness electron beams. Our transmission-mode tests show that, with single-crystal, high-purity diamonds, the peak current density is greater than 400 mA/mm2, while its average density can be more than 100 mA/mm2. The gain of the primary electrons easily exceeds 200, and is independent of their density within the practical range of DA applications. We observed the electron emission. The maximum emission gain measured was 40, and the bunch charge was 50 pC/0.5 mm2. There was a 35% probability of the emission of an electron from the hydrogenated surface in our tests. We identified a mechanism of slow charging of the diamond due to thermal ionization of surface states that cancels the applied field within it. We also demonstrated that a hydrogenated diamond is extremely robust.