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Laser Physics

Quantum optical measurements in ultracold gases: Macroscopic Bose-Einstein condensates

Thu, 2010-02-18 08:52 — Guest
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Abstract  
We consider an ultracold quantum degenerate gas in an optical lattice inside a cavity. This system represents a simple but
key model for “quantum optics with quantum gases,” where a quantum description of both light and atomic motion is equally
important. Due to the dynamical entanglement of atomic motion and light, the measurement of light affects the many-body atomic
state as well. The conditional atomic dynamics can be described using the Quantum Monte Carlo Wave Function Simulation method.
In this paper, we emphasize how this usually complicated numerical procedure can be reduced to an analytical solution after
some assumptions and approximations valid for macroscopic Bose-Einstein condensates (BEC) with large atom numbers. The theory
can be applied for lattices with both low filling factors (e.g. one atom per lattice site in average) and very high filling
factors (e.g., a BEC in a double-well potential). The purity of the resulting multipartite entangled atomic state is analyzed.

Quantum entanglement via superradiance of a Bose-Einstein condensate

Thu, 2010-02-18 08:52 — Guest
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points

Abstract  
We adopt the coherence and built-in swap mechanism in sequential superradiance as a tool for obtaining continuous-variable
(electric/magnetic fields) quantum entanglement of two counter-propagating pulses emitted from the two end-fire modes. In
the first-sequence, end-fire modes are entangled with the side modes. In the second sequence, this entanglement is swapped
to in between the two opposite end-fire modes. Additionally, we also examine the photon number correlations. No quantum correlations
is observed in this variable.

Frequency and phase synchronization in neuromagnetic cortical responses to flickering-color stimuli

Thu, 2010-02-18 08:52 — Guest
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points

Abstract  
In our earlier study dealing with the analysis of neuromagnetic responses (magnetoencephalograms—MEG) to flickering-color
stimuli for a group of control human subjects (9 volunteers) and a patient with photosensitive epilepsy (a 12-year old girl),
it was shown that Flicker-Noise Spectroscopy (FNS) was able to identify specific differences in the responses of each organism.
The high specificity of individual MEG responses manifested itself in the values of FNS parameters for both chaotic and resonant
components of the original signal. The present study applies the FNS cross-correlation function to the analysis of correlations
between the MEG responses simultaneously measured at spatially separated points of the human cortex processing the red-blue
flickering color stimulus.

Application of mid-infrared laser radiation for lithotripsy

Thu, 2010-02-18 08:52 — Guest
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points

Abstract  
The perforation effects of Er:YAG (2940 nm) and Ho:YAG (2100 nm) lasers radiation on human urinary stones model made from
compressed plaster and real human samples were compared in vitro. For mid-infrared laser radiation delivery the special COP/Ag
hollow glass waveguides were used. From the interaction experiments the perforation rates were derived and compared for both
lasers. From the results it can be evaluated that Er:YAG laser radiation is favourable in comparison with Ho:YAG laser in
case of artificial samples perforation efficiency.

Doped biocompatible layers prepared by laser

Thu, 2010-02-18 08:52 — Guest
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points

Abstract  
The contribution deals with KrF laser synthesis and study of doped biocompatible materials with focus on diamond-like carbon
(DLC) and hydroxyapatite (HA). Overview of materials used for dopation is given. Experimental results of study of HA layers
doped with silver are presented. Films properties were characterized using profilometer, SEM, WDX, XRD and optical transmission.
Content of silver in layers moved from 0.06 to 13.7 at %. The antibacterial properties of HA, silver and doped HA layers were
studied in vivo using Escherichia coli cells.

Diode-pumped 1028 nm Ytterbium-doped fiber laser with near 90% slope efficiency

Thu, 2010-02-18 08:52 — Guest
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Abstract  
Highly efficient laser action from an Ytterbium-doped fiber (YDF) is demonstrated using a fiber Bragg grating (FBG) in conjunction
with a 4% Fresnel reflection at room temperature. The YDF used is drawn from Yb2O3-doped preform, fabricated through deposition of porous layer of composition SiO2-GeO2 by the MCVD process in conjunction with a solution doping technique. The fabricated YDF has a core composition of 0.2 wt
% of Yb2O3, 1.8 wt % of Al2O3 and 23 wt % of GeO2 with a pump absorption of 9.0 dB/m. The fiber laser operates at wavelength of 1028 nm with a slope efficiency of 88% with
respect to the launched 976 nm pump power using the YDF length of 7 m.

Dual wavelength lasers

Thu, 2010-02-18 08:52 — Guest
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Abstract  
Dual wavelength lasers are discussed, covering fundamental aspects on the spectroscopy and laser dynamics of these systems.
Results on Tm:Ho:Er:YAG dual wavelength laser action (Ho at 2.1 μm and Er at 2.9 μm) as well as Nd:YAG (1.06 and 1.3 μm) are
presented as examples of such dual wavelength systems. Dual wavelength lasers are not common, but there are criteria that
govern their behavior. Based on experimental studies demonstrating simultaneous dual wavelength lasing, some general conclusions
regarding the successful operation of multi-wavelength lasers can be made.

Influence of electron irradiation on optical properties of scheelite crystals

Thu, 2010-02-18 08:52 — Guest
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points

Abstract  
Optical transmission spectra of nominally pure BaWO4 and SrMoO4 and doped BaWO4:La3+ and SrMoO4:Yb3+ crystals are measured after irradiation with a 6-MeV 5-μs pulse electron beam at room temperature. It is shown that the irradiation
effect strongly depends on the crystals composition, the type, and the concentrations of doping ions. Possible mechanisms
responsible for the spectra transformations and the correspondent formulas of chemical reactions addressing these mechanisms
are proposed.

Bismuth-based erbium-doped fiber as a gain medium for L-band amplification and Brillouin fiber laser

Thu, 2010-02-18 08:52 — Guest
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Abstract  
Bismuth-based erbium-doped fiber (Bi-EDF) is demonstrated as an alternative medium for optical amplification and nonlinear
applications. The bismuth glass host provides the opportunity to be doped heavily with erbium ions to allow a compact optical
amplifier design. The bismuth-based erbium-doped fiber amplifier (Bi-EDFA) is demonstrated to operate at wavelength region
from 1570 to 1620 nm using only a 215 cm long of gain medium. The maximum gain of 15.8 dB is obtained at signal wavelength
of 1610 nm with the corresponding noise figure of about 6.3 dB. A multi-wavelength laser comb is also demonstrated using a
stimulated Brillouin scattering in the 215 cm long Bi-EDF assisted by the 1480 nm pumping. The laser generates more than 40
lines of optical comb with a line spacing of approximately 0.08 at 1612.5 nm region using 152 mW of 1480 nm pump power.

Numerical calculation of strong-field laser-atom interaction: An approach with perfect reflection-free radiation boundary conditions

Thu, 2010-02-18 08:52 — Guest
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points

Abstract  
The time-dependent, single-particle Schrödinger equation with a finite-range potential is solved numerically on a three-dimensional
spherical domain. In order to correctly account for outgoing waves, perfect reflection-free radiation boundary conditions
are used on the surface of a sphere. These are computationally most effective if the particle wavefunction is expanded in
the set of spherical harmonics and computations are performed in the Kramers-Henneberger accelerated frame. The method allows
one to solve the full ionization dynamics in intense laser fields within a small region of atomic dimensions.

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