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Copyright of Óptica Pura y Aplicada is the property of Sociedad Espanola de Optica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Presents information on the performance of materials processing to the applications of a pulsed cold cathode electron gun. Information on the model of the cold cathode electron gun discharge; Details on the material interactions in relation to the electron beam; Conclusion of the experiment.

We present a photon counting experiment designed for an undergraduate physics laboratory. The statistics of the number of photons of a pseudo-thermal light source is studied in two limiting cases: much longer and much shorter than the coherence time, giving Poisson and Bose-Einstein distributions, respectively. The experiment can be done in a reasonable time using a digital oscilloscope without the need of counting boards. The use of the oscilloscope has the advantage of allowing the storage of the data for further processing. The stochastic nature of the detection phenomena adds additional value because students are forced to do data processing and analysis. [ABSTRACT FROM AUTHOR]

Choroid plexus xanthogranulomas are uncommon lesions that occur almost exclusively in adults; most of them constitute incidental autopsy findings. A case of symptomatic bilateral xanthogranulomas of choroid plexus in a 6 year-old girl with progressive visual loss is reported. Theories on the pathogenesis of this entity are reviewed. [ABSTRACT FROM AUTHOR]

We report the first measurement of the temperature dependence of the relative threshold carrier density, Nth, in InGaAsP-InP lasers. The characteristic temperature T′0, defined by 1/T0 ≡d ln Nth/dT, which is independent of nonradiative recombination mechanisms, is determined by transient pumping of a simple double heterostructure laser with optical pulses short ([bar_over_tilde:_approx._equal_to]100 ps) compared to the carrier lifetime (2-3 ns). A single T′0 as large as 120 K describes an exponential threshold dependence on temperature over a wide temperature range (160-370 K). Comparison with steady state (300 ns) excitation of the same samples shows that nonradiative recombination is responsible for the commonly observed injection laser break from a low-temperature T0[bar_over_tilde:_approx._equal_to]100 K to the poorer room-temperature T0[bar_over_tilde:_approx._equal_to]65 K. The measured T0 is smaller than a previously calculated value of approximately 200 K. [ABSTRACT FROM AUTHOR]

We have measured the temperature dependence of the threshold current of an InGaAsP injection laser pumped by 130-ps electrical pulses. By comparing the data with the empirical rule Ith=I0 exp(T/T0), we have observed a T0 of 148 K. The results indicate that we can partially separate carrier depletion processes, e.g., spontaneous radiative, Auger, or other nonradiative recombination, and carrier leakage from the fast stimulated emission process, hence, eliminate their effect on the temperature stability of the threshold current. [ABSTRACT FROM AUTHOR]

In this work, we characterized streptavidin-conjugated quantum dots (QDs) manufactured by Quantum Dot Corporation. We present data on: (1) two-photon excitation; (2) fluorescence lifetimes; (3) ensemble and single QD emission anisotropy; (4) QDs as donors for Forster resonance energy transfer (FRET); and (5) spectral conversion of QDs exposed to high-intensity illumination. We also demonstrate the utility of QDs for (1) imaging the binding and uptake of biotinylated transferrin on living cells, and (2) resolving by fluorescence lifetime imaging microscopy (FLIM) signals originating from QDs from those of spatially and spectrally overlapping visible fluorescent proteins (VFPs)., ((c) 2005 Wiley-Liss, Inc.)

A compact pulse stretcher using curved diffraction gratings is presented. It introduces positive group-delay dispersion and can operate in conjunction with a standard grating-pair compressor in chirped-pulse amplification systems. It presents several advantages over other systems proposed: It has no degrees of freedom and so is not highly sensitive to alignment errors, it is easy to align, it has a compact and robust design, and it uses standard optics. The frequency-dependent delay, dispersions up to third order, and the design parameters of the stretcher-compressor system that will yield good matching are analyzed. Examples of design specifications for a 40-fs pulse with a central wavelength of lambda=800 nm are given.

A soft-x-ray Mach-Zehnder interferometer configuration that makes use of the time delay introduced by diffraction gratings to conduct single-shot measurements of the linewidth of soft-x-ray laser amplifiers is proposed and analyzed. The scheme was experimentally demonstrated in the near-IR region of the spectrum by measurement of the mode separation of a semiconductor laser. A symmetric configuration with compensated time delays that can be implemented for plasma diagnostics and for evaluating soft-x-ray optics is also discussed.

A new type of grating compressor capable of compensating, in principle, for any arbitrary group-delay dispersion is described. The system relies on a specially designed grating with a variable groove spacing along its surface as well as a variable angle of incidence. In this manner each wavelength actually sees a different grating, always at Littrow incidence, that gives rise to distinct group delays. The design equations are derived, and the particular case of a cubic compressor is discussed. It is shown that, within practical limits, both quadratic and cubic terms can be simultaneously compensated for in typical optical fibers.

A prism placed at the minimum deviation angle inserted into a dye laser cavity acts as an optical reductor of the variation of the angle between the tuning mirror and the grating, thus facilitating the mechanical requirements to obtain a high resolution (0.15-pm) wavelength scan.

A direct measurement of the amplitude and the phase of a femtosecond light pulse is performed for the first time to our knowledge. The measurement is made in the frequency domain, and the time dependence of the field can be easily obtained by a Fourier transform. The technique relies on a pulse synthesis scheme to unravel the frequency dependence of the phase. A mask filters the spectrum, which gives rise to a pulse with a measurable temporal profile related to the frequency dependence of the phase. In particular, with a rectangular slit the time delay of the synthesized pulse is the first derivative of the phase with respect to the frequency of the original pulse at the central frequency of the filter. The amplitude of the spectrum is obtained from the power spectrum.