158 research outputs found
Preparation of an Exponentially Rising Optical Pulse for Efficient Excitation of Single Atoms in Free Space
We report on a simple method to prepare optical pulses with exponentially
rising envelope on the time scale of a few ns. The scheme is based on the
exponential transfer function of a fast transistor, which generates an
exponentially rising envelope that is transferred first on a radio frequency
carrier, and then on a coherent cw laser beam with an electro-optical phase
modulator (EOM). The temporally shaped sideband is then extracted with an
optical resonator and can be used to efficiently excite a single Rb-87 atom.Comment: 3 pages, 4 figures, small technical not
Doppler-free approach to optical pumping dynamics in the electric quadrupole transition of Cesium vapor
The electric quadrupole transition is investigated in
Cesium vapor at room temperature via nonlinear Doppler-free 6P-6S-5D
three-level spectroscopy. Frequency-resolved studies of individual E2 hyperfine
lines allow one to analyze optical pumping dynamics, polarization selection
rules and line intensities. It opens the way to studies of transfer of light
orbital angular momentum to atoms, and the influence of metamaterials on E2
line spectra.Comment: 4 pages, 5 figures, minor updates from previous versio
Excitation of a single atom with exponentially rising light pulses
We investigate the interaction between a single atom and optical pulses in a
coherent state with a controlled temporal envelope. In a comparison between a
rising exponential and a square envelope, we show that the rising exponential
envelope leads to a higher excitation probability for fixed low average photon
numbers, in accordance to a time-reversed Weisskopf-Wigner model. We
characterize the atomic transition dynamics for a wide range of the average
photon numbers, and are able to saturate the optical transition of a single
atom with ~50 photons in a pulse by a strong focusing technique. For photon
numbers of ~1000 in a 15ns long pulse, we clearly observe Rabi oscillations.Comment: 5 pages, 6 figure
Tailoring optical metamaterials to tune the atom-surface Casimir-Polder interaction
Metamaterials are fascinating tools that can structure not only surface
plasmons and electromagnetic waves but also electromagnetic vacuum
fluctuations. The possibility of shaping the quantum vacuum is a powerful
concept that ultimately allows engineering the interaction between macroscopic
surfaces and quantum emitters such as atoms, molecules or quantum dots. The
long-range atom-surface interaction, known as Casimir-Polder interaction, is of
fundamental importance in quantum electrodynamics but also attracts a
significant interest for platforms that interface atoms with nanophotonic
devices. Here we perform a spectroscopic selective reflection measurement of
the Casimir-Polder interaction between a Cs(6P_{3/2}) atom and a nanostructured
metallic planar metamaterial. We show that by engineering the near-field
plasmonic resonances of the metamaterial, we can successfully tune the
Casimir-Polder interaction, demonstrating both a strong enhancement and
reduction with respect to its non-resonant value. We also show an enhancement
of the atomic spontaneous emission rate due to its coupling with the evanescent
modes of the nanostructure. Probing excited state atoms next to nontrivial
tailored surfaces is a rigorous test of quantum electrodynamics. Engineering
Casimir-Polder interactions represents a significant step towards atom trapping
in the extreme near field, possibly without the use of external fields.Comment: 21 pages, 9 figure
Coupling of atomic quadrupole transitions with resonant surface plasmons
We report on the coupling of an electric quadrupole transition in atom with
plasmonic excitation in a nanostructured metallic metamaterial. The quadrupole
transition at 685 nm in the gas of Cesium atoms is optically pumped, while the
induced ground state population depletion is probed with light tuned on the
strong electric dipole transition at 852 nm. We use selective reflection to
resolve the Doppler-free hyperfine structure of Cesium atoms. We observed a
strong modification of the reflection spectra at the presence of metamaterial
and discuss the role of the spatial variation of the surface plasmon polariton
on the quadrupole coupling.Comment: 6 pages, 5 figure
A new code for optical code division multiple access systems
A new code structure based on Double-Weight (DW) code families is proposed for Spectral-Amplitude-Coding Optical Code Division Multiple Access (OCDMA) system. The constraint of a constant weight of 2 for the DW code can be relaxed using a mapping technique. By using this technique, codes that have a larger number of weight can be developed. Modified Double-Weight (MDW) Code is another variation of a DW code family that can has a variable weight greater than two. The MDW code possesses ideal cross-correlation properties and exists for every natural number n. A much better performance can be provided by using the MDW code compared to the existing codes such as Hadamard and Modified Frequency-Hopping (MFH) codes. This has been demonstrated from the theoretical analysis and simulation
Design configuration of encoder and decoder modules for modified double weight (MDW) code spectral amplitude coding (SAC) optical code division multiple access (OCDMA) based on fiber Bragg gratings
In this work, we are proposing the serial and parallel configurations of encoder and decoder modules to encode and decode a new developed spectral amplitude coding (SAC) known as modified double weight (MDW) code for optical code division multiple access (OCDMA) system. This coding scheme is designed in a way to decrease the number of FBGs used in the encoder and decoder modules and to maintain the cross-correlation parameter to 1
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