Search results for "TUNABLE"

Isobar suppression in AMS using laser photodetachment

2008

Abstract We are investigating the possibility of using laser photodetachment of negative atomic and molecular ions as an additional isobaric selection filter in accelerator mass spectrometry. The aim of this study is to find a possibility to further improve the detection limit for long-lived heavy radionuclides at AMS facilities. We will focus on the astrophysical relevant radionuclide 182Hf, which is one of the isotopes measured with the 3 MV tandem AMS facility VERA (Vienna Environmental Research Accelerator) at the University of Vienna. Laser-induced isobar suppression is also of importance for radioactive-beam facilities. The present detection limit for measuring the isotope ratio 182Hf…

On the Secondary Discharge of an Atmospheric-Pressure Pulsed DBD in He with Impurities

2008

The secondary discharge was induced at the end of a slow-falling voltage flank, when a semisine monopolar pulse voltage excites the dielectric-barrier discharge. Formation and properties of the secondary discharge with respect to different dielectric materials such as glass, ceramic, and polyethylene theraphtalate were studied. The tunable diode laser absorption spectrometry (at 777.194 nm) was used to analyze the time-space distribution of the density of the atomic oxygen in metastable state (35S2 rarr 35P3) in addition to both discharge voltage and discharge current versus time. The secondary discharge is always formed, and its amplitude, as well as the amplitude of the main discharge, de…

Injection-Locked Flashlamp-Pumped Dye Lasers Of Very Narrow Linewidth

1988

Very high spectral quality flashlamp-pumped dye lasers are described, in which spectral narrowing is achieved by injection-locking of pulsed amplifying cavities to the wavelength of low power single-mode cw lasers. With the help of a fast electronic stabilization of the cavity length, we obtain a reliable complete injection. Peak powers up to 12 kW in 300 ns at a bandwith of 6 MHz are achieved over a 150 nm tuning range between 572 and 722 nm. The repetition rate is 10 Hz, limited mainly by the circulating pumps. Applications of these lasers are found in high resolution coherent Raman spectroscopy and nonlinear difference frequency mixing.

Diode-pumped bulk Er:Yb:Glass 1.54μm pulsed laser with 1.2J output and 25% optical efficiency

2002

We report a pulsed transversely diode-pumped compact Er:Yb:Glass laser of uncomplicated design, delivering output energy of approx. 1.2J in free-running operation and 25% optical slope efficiency.

Potentialities of glass air-clad micro- and nanofibers for nonlinear optics

2010

Micro- and nanofibers constitute an attractive platform for testing nonlinear devices with millimeter size in a simple and flexible fashion, with potential applications in ultra-fast all-optical communications. In this article, we present challenges that must be addressed and targets that can be reached using such a platform. We describe a tunable laser source capable of delivering pulses with a kilowatt peak power and a sub-0.1-nm linewidth that is specially designed for the study of resonant devices such as the nonlinear loop resonator. Experimental and simulation results are presented for silica microfiber based nonlinear devices. The prospect of developing hybrid devices combining highl…

Acoustically Q-switched single-frequency fibre laser

2007

A dual-wavelength tunable laser with superimposed fiber Bragg gratings

2013

We report a dual-wavelength tunable fiber laser. The cavity is formed by two superimposed fiber Bragg gratings (FBGs) and a temperature tunable high-birefringence fiber optical loop mirror (FOLM). FBGs with wavelengths of 1548.5 and 1538.5 nm were printed in the same section of a fiber using two different masks. The superimposed FBGs were placed on a mechanical mount that allows stretch or compression of the FBGs. As a result of the FBG strain both lines are shifted simultaneously. Dual-wavelength generation requires a fine adjustment of the cavity loss for both wavelengths.

Zero permeability and zero permittivity band gaps in 1D metamaterial photonic crystals

2007

We consider layered heterostructures combining ordinary positive index materials and dispersive metamaterials. We show that these structures can exhibit a new type of photonic gap around frequencies where either the magnetic permeability \mu or the electric permittivity \epsilon of the metamaterial is zero. Although the interface of a semi-infinite medium with zero refractive index (a condition attained either when \mu= 0 or when \epsilon= 0) is known to give full reflectivity for all incident polarizations, here we show that a gap corresponding to \mu = 0 occurs only for TE polarized waves, whereas a gap corresponding to \epsilon = 0 occurs only for TM polarized waves. These band gaps are …

Luminescence properties of nonbridging oxygen hole centers at the silica surface

2009

Abstract Two variants of the surface-nonbridging oxygen hole center, ( Si–O)3Si–O• and ( Si–O)2(H–O)Si–O•, stabilized in porous films of silica nano-particles were investigated by time resolved luminescence excited in the visible and UV spectral range by a tunable laser system. Both defects emit a photoluminescence around 2.0 eV with an excitation spectrum evidencing two maxima at 2.0 and 4.8 eV, this emission decreases by a factor ∼2 on increasing the temperature from 8 up to 290 K. However, the different local structure influences the emission lineshape, the quantum yield and the decay lifetime. Such peculiarities are discussed on the basis of the symmetry properties of these defects.

Luminescence features of nonbridging oxygen hole centres in silica probed by site-selective excitation with tunable laser

2008

Time-resolved photoluminescence at 1.9 eV associated with the nonbridging oxygen hole centre (NBOHC) in silica was investigated under excitation with a ns pulsed laser system, tunable in the visible range. Mapping of the excitation/emission pattern evidences the site-selective excitation of the resonant zero phonon line (ZPL) transition due to its weak coupling with the stretching mode of dangling oxygen. Decay of ZPL follows an exponential law with lifetime of 15.3 μs, which provides a precise measure of the electronic transition probability of a single NBOHC.