36 research outputs found
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
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
Plasmono-Atomic Interactions on a Fiber Tip
Light-atom interaction can be engineered by interfacing atoms with various
specially designed media and optical fibers are convenient platforms for
realization of compact interfaces. Here, we show that an optical fiber sensor
bearing a plasmonic metasurface at its tip can be used to detect modifications
of the Doppler-free hyperfine atomic spectra induced by coupling between atomic
and plasmonic excitations. We observed the inversion of the phase modulation
reflectivity spectra of Cesium vapor in presence of the metamaterial. This work
paves the way for future compact hybrid atomic devices with a cleaved tip as
substrate platform to host various two-dimensional materials.Comment: 12 pages, 3 figure
Image reconstruction through a multimode fiber with a simple neural network architecture
Multimode fibers (MMFs) have the potential to carry complex images for
endoscopy and related applications, but decoding the complex speckle patterns
produced by mode-mixing and modal dispersion in MMFs is a serious challenge.
Several groups have recently shown that convolutional neural networks (CNNs)
can be trained to perform high-fidelity MMF image reconstruction. We find that
a considerably simpler neural network architecture, the single hidden layer
dense neural network, performs at least as well as previously-used CNNs in
terms of image reconstruction fidelity, and is superior in terms of training
time and computing resources required. The trained networks can accurately
reconstruct MMF images collected over a week after the cessation of the
training set, with the dense network performing as well as the CNN over the
entire period.Comment: 17 pages, 10 figure
Retrieving positions of closely packed sub-wavelength nanoparticles from their diffraction patterns
Distinguishing two objects or point sources located closer than the Rayleigh
distance is impossible in conventional microscopy. Understandably, the task
becomes increasingly harder with a growing number of particles placed in close
proximity. It has been recently demonstrated that subwavelength nanoparticles
in closely packed clusters can be counted by AI-enabled analysis of the
diffraction patterns of coherent light scattered by the cluster. Here we show
that deep learning analysis can determine the actual position of the
nanoparticle in the cluster of subwavelength particles from a sing-shot
diffraction pattern even if they are separated by distances below the Rayleigh
resolution limit of a conventional microscope.Comment: 6 pages, 3 figure
Atom/light interaction at the interface of metamaterials
An exciting frontier in the research field of atomic physics is the active engineering of the atomic environment, motivated by the prospect of applications in quantum information science, many-body physics simulation, atom-based metrology and sensor technology. To this end, one active direction in the atomic community is the manipulation of atoms at nanoscale distance from surface plasmons, utilizing the strong confinement of electric field of the surface plasmon to realize atom-trapping, single photon emitter source and strongly coupled system. Towards these goals, we experimentally investigated the coupling of hot atomic Cesium vapor with plasmonic metamaterials. First, we demonstrate tailoring of metamaterial for the tuning of atom-surface Casimir Polder interaction. Next, we realize atom-metamaterial interaction on a fiberized platform. In the atomic spectroscopy realm, we devise a method to study low-lying dipole-forbidden electric quadrupole transition with a non-linear pump-probe technique. Finally, we investigate the possible enhancement of an electric quadrupole transition in the vicinity of a plasmonic metamaterial. Overall, these advances are significant contributions towards achieving subwavelength trapping of atoms at close distance from surface, integrating of fiberized atomic systems for mainstream applications, enabling the studies of the transfer of orbital angular momentum of light to dipole-forbidden transitions and setting forth the investigation direction for dipole-forbidden transitions in an atom-plasmonic system.Doctor of Philosoph
Photoconductive terahertz generation and detection.
In this work, replication of results on measurement of temporal waveform of Terahertz pulses generated by a commercial photoconductive antenna is reported. Experiment analogue to free space Time-Domain Spectroscopy is carried out for the waveform measurement. Fast Fourier Transform is then performed to obtain the frequency spectrum of the Terahertz pulse. The results are compared with the test report of the commercial photoconductive antenna.Bachelor of Science in Physic