Virtual Journal of Laser

Uniform-field transverse electroreflectance using a mode-locked laser and a radio-frequency bias

Tue, 09 Mar 2010 15:00:15 -0800

J. K. Wahlstrand, H. Zhang, and S. T. Cundiff
We describe a technique for transverse electroreflectance that uses broadband optical pulses from a mode-locked laser and a rapidly oscillating bias with a frequency near half the laser repetition rate. Since the electrodes are electrically isolated from the sample, highly nonuniform trap-enhanced f ... [Appl. Phys. Lett. 96, 101104 (2010)] published Tue Mar 9, 2010.

Angular and prism coupling refractive enhancement in dye solar cells

Tue, 09 Mar 2010 15:00:14 -0800

Lorenzo Dominici, Luigi Vesce, Daniele Colonna, Francesco Michelotti, Thomas M. Brown et al.
We quantify the strong dependence of photocurrent on the angle of incidence of light in a dye solar cell (DSC). Under laser illumination the photocurrent increases for large incidence angles. The enhancements are different upon using or not a coupling prism. They are explained with a model including ... [Appl. Phys. Lett. 96, 103302 (2010)] published Tue Mar 9, 2010.

Spectroscopic determination of rotational temperature in C_2H_4/C_2H_2/O_2 flames for diamond growth with and without tunable CO_2 laser excitation

Wed, 10 Mar 2010 21:00:00 -0800

X. N. He, X. K. Shen, T. Gebre, Z. Q. Xie, L. Jiang, Y. F. Lu
Optical emission spectroscopy (OES) and spectroscopic temperature determination were carried out to study C_2H_4/C_2H_2/O_2 flames used for diamond deposition with and without an excitation by a wavelength-tunable CO_2 laser. Strong emissions from C_2 and CH radicals were observed in the visible ... [Appl. Opt. 49, 1555-1562 (2010)]

Laser optical gas sensor by photoexcitation effect on refractive index

Wed, 10 Mar 2010 21:00:00 -0800

Geunsik Lim, Upul P. DeSilva, Nathaniel R. Quick, Aravinda Kar
Laser optical gas sensors are fabricated by using the crystalline silicon carbide polytype 6H-SiC, which is a wide-bandgap semiconductor, and tested at high temperatures up to 650°C. The sensor operates on the principle of semiconductor optics involving both the semiconductor and optical ... [Appl. Opt. 49, 1563-1573 (2010)]

Generation of ribbons, helicoids, and complex Scherk surfaces in laser-matter interactions

Mon, 08 Mar 2010 16:00:00 -0800

Author(s): S. Lugomer and Y. Fukumoto
Motivated by a diversity of the shape instability phenomena in condensed-matter physics, we study the formation of elastic ribbon structures and transformation into helicoidal structures. Using the multipulse laser-matter interaction with the Co-coated surface, a one-dimensional high-density vortex-...
[Phys. Rev. E 81, 036311] Published Tue Mar 09, 2010

Control of the high harmonic generation spectra by changing the molecule-laser field relative orientation

Tue, 02 Mar 2010 21:00:00 -0800

Rosalba Daniele, Francesca Morales, Giuseppe Castiglia, Pietro Paolo Corso, Gianfranco Orlando, Emilio Fiordilino
The time dependent Schrödinger equation of a homonuclear diatomic molecule in the presence of a linearly polarized laser field is numerically solved by means of a split-operator parallel code. The calculations are carried out by assuming a single active electron model with fixed nuclei; a ... [J. Opt. Soc. Am. B 27, 625-630 (2010)]

Few-cycle optical pulse production from collimated femtosecond laser beam filamentation

Mon, 08 Mar 2010 21:00:00 -0800

Daria Uryupina, Maria Kurilova, Anna Mazhorova, Nikolay Panov, Roman Volkov, Stepan Gorgutsa, Olga Kosareva, Andrei Savel'ev, See Leang Chin
A scheme for stable shot-to-shot few-cycle pulse production has been realized by launching an initially collimated laser beam into a gas tube. We found that the optimum parameters for the sevenfold compression of 55 fs, 5 mJ, Ti:Sapphire laser pulses are the following: 0.8-0.9 atm argon gas ... [J. Opt. Soc. Am. B 27, 667-674 (2010)]

Sensitive detection of metals in water using laser-induced breakdown spectroscopy on wood sample substrates

Mon, 08 Mar 2010 21:00:00 -0800

Zhijiang Chen, Yogesh Godwal, Ying Yin Tsui, Robert Fedosejevs
Water contaminated with toxic heavy metals can be a great risk to humans. Laser-induced breakdown spectroscopy (LIBS) is a promising candidate to monitor heavy metals in aqueous solutions on site, but the sensitivity is still a major problem. To perform sensitive analysis of analyte metals in ... [Appl. Opt. 49, C87-C94 (2010)]

Development of microwave-enhanced spark-induced breakdown spectroscopy

Mon, 08 Mar 2010 21:00:00 -0800

Yuji Ikeda, Ahsa Moon, Masashi Kaneko
We propose microwave-enhanced spark-induced breakdown spectroscopy with the same measurement and analysis processes as in laser-induced breakdown spectroscopy, but with a different plasma generation mechanism. The size and lifetime of the plasma generated can contribute to increased measurement ... [Appl. Opt. 49, C95-C100 (2010)]

Double-pulse and single-pulse laser-induced breakdown spectroscopy for distinguishing between gaseous and particulate phase analytes

Mon, 08 Mar 2010 21:00:00 -0800

Michael E. Asgill, Michael S. Brown, Kyle Frische, William M. Roquemore, David W. Hahn
We explore the use of a combination of double-pulse and single-pulse laser-induced breakdown spectroscopy (LIBS) methodologies as a means of differentiating between solid-phase and gaseous-phase analytes (namely, carbon) in an aerosol stream. A range of spectral data was recorded for double-pulse ... [Appl. Opt. 49, C110-C119 (2010)]

Archaeological applications of laser-induced breakdown spectroscopy: an example from the Coso Volcanic Field, California, using advanced statistical signal processing analysis

Tue, 09 Mar 2010 21:00:00 -0800

Jeremiah J. Remus, Jennifer L. Gottfried, Russell S. Harmon, Anne Draucker, Dirk Baron, Robert Yohe
Over the past quarter century, multielement chemical analysis has become a common means for attributing the provenance of archaeological materials. The Coso Volcanic Field (CVF) in California, USA, contains at least 38 high-silica rhyolite domes, many of which contain obsidian glass that has been ... [Appl. Opt. 49, C120-C131 (2010)]

Laser-induced onset of electrospinning

Mon, 08 Mar 2010 16:00:00 -0800

Author(s): R. Sahay, C. J. Teo, and S. T. Thoroddsen
We present a method to start electrospinning from a polymeric drop. This method uses a pulsed laser which is focused inside the drop close to the liquid surface. The pulse cavitates the liquid and produces a protrusion from the tip of the drop. The protrusion narrows by drainage and vertical stretch...

[Phys. Rev. E 81, 035302] Published Tue Mar 09, 2010

Photoassociation spectra and the validity of the dipole approximation for weakly bound dimers

Sun, 07 Mar 2010 16:00:00 -0800

Author(s): Daniel G. Cocks and Ian B. Whittingham
Photoassociation (PA) of ultracold metastable helium to the 2s2p manifold is theoretically investigated using a nonperturbative close-coupled treatment in which the laser coupling is evaluated without assuming the dipole approximation. The results are compared with our previous study [D. G. Cocks an...
[Phys. Rev. A 81, 033406] Published Mon Mar 08, 2010

Two-dimensional atom localization in a four-level tripod system in laser fields

Sun, 07 Mar 2010 16:00:00 -0800

Author(s): Vladimir Ivanov and Yuri Rozhdestvensky
We propose a scheme for two-dimensional (2D) atom localization in a four-level tripod system under an influence of two orthogonal standing-wave fields. Position information of the atom is retained in the atomic internal states by an additional probe field either of a standing or of a running wave. I...
[Phys. Rev. A 81, 033809] Published Mon Mar 08, 2010

Spatiotemporal polarization gradients in phase-bearing light

Sun, 07 Mar 2010 16:00:00 -0800

Author(s): V. E. Lembessis and M. Babiker
It is shown how the interference of two circularly polarized laser beams endowed with orbital angular momentum can give rise to spatial and temporal polarization gradients, displaying axial as well as angular symmetry properties. Illustrations are given with reference to circularly polarized Laguerr...
[Phys. Rev. A 81, 033811] Published Mon Mar 08, 2010

Growth modes of ZnO nanostructures from laser ablation

Mon, 08 Mar 2010 16:00:11 -0800

I. Amarilio-Burshtein, S. Tamir, and Y. Lifshitz
ZnO nanowires (NWs) and other nanostructures were grown by laser ablation of a ZnO containing target onto different substrates with and without the presence of an Au catalyst. The morphology and structure of the NWs were studied using high resolution scanning and transmission electron microscopes [i ... [Appl. Phys. Lett. 96, 103104 (2010)] published Mon Mar 8, 2010.

Anisotropic heat propagation velocity in quantum cascade lasers

Mon, 08 Mar 2010 14:00:16 -0800

Miriam S. Vitiello and Gaetano Scamarcio
We report on the time-resolved measurement of the in-plane (v) and cross-plane (v) components of the heat transfer velocity in GaAs/AlGaAs quantum-cascade heterostructures. We compared the heating and cooling stages both in the active region and in the substrate with models of heat transfer in nanos ... [Appl. Phys. Lett. 96, 101101 (2010)] published Mon Mar 8, 2010.

Si/SiGe quantum cascade superlattice designs for terahertz emission

Mon, 08 Mar 2010 12:00:30 -0800

G. Matmon, D. J. Paul, L. Lever, M. Califano, Z. Ikonic et al.
Quantum cascade lasers (QCLs) are compact sources that have demonstrated high output powers at terahertz (THz) frequencies. To date, all THz QCLs have been realized in III-V materials. Results are presented from SiGe quantum cascade superlattice designs emitting at around 3 THz which have been grown ... [J. Appl. Phys. 107, 053109 (2010)] published Mon Mar 8, 2010.

Stress and doping uniformity of laser crystallized amorphous silicon in thin film silicon solar cells

Mon, 08 Mar 2010 12:00:29 -0800

R. M. B. Agaiby, M. Becker, S. B. Thapa, U. Urmoneit, A. Berger et al.
Simultaneous and locally resolved determination of the mechanical stress variation and the free hole concentration using Raman spectroscopy is demonstrated in laser crystallized amorphous silicon layers. Such layers are often used for the fabrication of thin film solar cells, e.g., on borosilicate g ... [J. Appl. Phys. 107, 054312 (2010)] published Mon Mar 8, 2010.

Morphological evolution of pulsed laser deposited ZrO thin films

Mon, 08 Mar 2010 12:00:27 -0800

R. Alvarez, A. Palmero, L. O. Prieto-Lopez, F. Yubero, J. Cotrino et al.
Morphological evolution of ZrO thin films deposited during pulsed laser deposition of Zr in O atmosphere has been experimentally studied at two different film deposition temperatures, 300 and 873 K. The roughness exponent, alpha, the growth exponent, beta, the coarsening exponent, 1/z, and the expon ... [J. Appl. Phys. 107, 054311 (2010)] published Mon Mar 8, 2010.

Laser-catalyzed spin-exchange process in a Bose-Einstein condensate

Sun, 07 Mar 2010 16:00:00 -0800

Author(s): H. Jing, Y. Jiang, Weiping Zhang, and P. Meystre
We show theoretically that it is possible to optically control collective spin-exchange processes in spinor Bose condensates through virtual photoassociation. The interplay between optically induced spin exchange and spin-dependent collisions provides a flexible tool for the control of atomic spin d...

[Phys. Rev. A 81, 031603] Published Mon Mar 08, 2010

Passive mode-locking of a diode-pumped Nd:YVO_4 laser by intracavity SHG in PPKTP

Sun, 07 Mar 2010 21:00:00 -0800

Hristo Iliev, Danail Chuchumishev, Ivan Buchvarov, Valentin Petrov
Experimental results on passive mode-locking of a Nd:YVO_4 laser using intracavity frequency doubling in periodically poled KTP (PPKTP) crystal are reported. Both, negative cascaded χ^(2) lensing and frequency doubling nonlinear mirror (FDNLM) are exploited for the laser mode-locking. The ... [Opt. Express 18, 5754-5762 (2010)]

Anomalous State Sandwiched between Fermi Liquid and Charge Ordered Mott-Insulating Phases of Ti_{4} O_{7}

Sun, 07 Mar 2010 16:00:00 -0800

Author(s): M. Taguchi, A. Chainani, M. Matsunami, R. Eguchi, Y. Takata, M. Yabashi, K. Tamasaku, Y. Nishino, T. Ishikawa, S. Tsuda, S. Watanabe, C.-T. Chen, Y. Senba, H. Ohashi, K. Fujiwara, Y. Nakamura, H. Takagi, and S. Shin
The Magnéli phase Ti_{4} O_{7} exhibits two sharp jumps in resistivity with coupled structural transitions as a function of temperature at T_{c1} ∼142 K and T_{c2} =154 K. We have studied electronic structure changes across the two transitions using 7 eV laser, soft x-ray, and hard x-r...
[Phys. Rev. Lett. 104, 106401] Published Mon Mar 08, 2010

Ho:YAG ceramic laser pumped by Tm:YLF lasers at room temperature

Sun, 07 Mar 2010 20:41:00 -0800

Lasers from Ho:YAG ceramic were reported in this paper. The Ho:YAG ceramic slab was end-pumped by a Tm:YLF laser whose central wavelength was 1.91 [mu]m. At room temperature, with doping concentrations of 1 at.% Ho:YAG ceramic slab, continuous wave output power of 1.2 W at 2.09 [mu]m was obtained under the absorbed pump power of 5 W, corresponding to a slope efficiency of 42.6% and a conversion efficiency of 24%. (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)

All-fiber pulsewidth tunable actively Q-switched erbium fiber laser using abrupt-tapered Mach-Zehnder block filter

Sun, 07 Mar 2010 20:41:00 -0800

We demonstrate pulsewidth tunable Q-switched erbium fiber lasers using in-line high extinction ratio (>30 dB) abrupt-tapered fiber Mach-Zehnder block filter and tunable Fabry-Perot filter in laser cavity. The pulsewidth can be tuning over 78 ns - 23 ms. (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)