38 research outputs found
Polarization shaping for control of nonlinear propagation
We study the nonlinear optical propagation of two different classes of
space-varying polarized light beams -- radially symmetric vector beams and
Poincar\'e beams with lemon and star topologies -- in a rubidium vapour cell.
Unlike Laguerre-Gauss and other types of beams that experience modulational
instabilities, we observe that their propagation is not marked by beam breakup
while still exhibiting traits such as nonlinear confinement and self-focusing.
Our results suggest that by tailoring the spatial structure of the
polarization, the effects of nonlinear propagation can be effectively
controlled. These findings provide a novel approach to transport high-power
light beams in nonlinear media with controllable distortions to their spatial
structure and polarization properties.Comment: 5 pages, and 4 figure
Nondestructive Measurement of Orbital Angular Momentum for an Electron Beam
Free electrons with a helical phase front, referred to as "twisted"
electrons, possess an orbital angular momentum (OAM) and, hence, a quantized
magnetic dipole moment along their propagation direction. This intrinsic
magnetic moment can be used to probe material properties. Twisted electrons
thus have numerous potential applications in materials science. Measuring this
quantity often relies on a series of projective measurements that subsequently
change the OAM carried by the electrons. In this Letter, we propose a
nondestructive way of measuring an electron beam's OAM through the interaction
of this associated magnetic dipole with a conductive loop. Such an interaction
results in the generation of induced currents within the loop, which are found
to be directly proportional to the electron's OAM value. Moreover, the electron
experiences no OAM variations and only minimal energy losses upon the
measurement, and, hence, the nondestructive nature of the proposed technique.Comment: 5 pages, 3 figures, and supplemental material that is comprised of
text and 4 figure
Measuring the orbital angular momentum spectrum of an electron beam
Electron waves that carry orbital angular momentum (OAM) are characterized by a quantized and unbounded magnetic dipole moment parallel to their propagation direction. When interacting with magnetic materials, the wavefunctions of such electrons are inherently modified. Such variations therefore motivate the need to analyse electron wavefunctions, especially their wavefronts, to obtain information regarding the material’s structure. Here, we propose, design and demonstrate the performance of a device based on nanoscale holograms for measuring an electron’s OAM components by spatially separating them. We sort pure and superposed OAM states of electrons with OAM values of between −10 and 10. We employ the device to analyse the OAM spectrum of electrons that have been affected by a micron-scale magnetic dipole, thus establishing that our sorter can be an instrument for nanoscale magnetic spectroscopy
Scalable photonic integrated circuits for programmable control of atomic systems
Advances in laser technology have driven discoveries in atomic, molecular,
and optical (AMO) physics and emerging applications, from quantum computers
with cold atoms or ions, to quantum networks with solid-state color centers.
This progress is motivating the development of a new generation of
"programmable optical control" systems, characterized by criteria (C1) visible
(VIS) and near-infrared (IR) wavelength operation, (C2) large channel counts
extensible beyond 1000s of individually addressable atoms, (C3) high intensity
modulation extinction and (C4) repeatability compatible with low gate errors,
and (C5) fast switching times. Here, we address these challenges by introducing
an atom control architecture based on VIS-IR photonic integrated circuit (PIC)
technology. Based on a complementary metal-oxide-semiconductor (CMOS)
fabrication process, this Atom-control PIC (APIC) technology meets the system
requirements (C1)-(C5). As a proof of concept, we demonstrate a 16-channel
silicon nitride based APIC with (5.80.4) ns response times and -30 dB
extinction ratio at a wavelength of 780 nm. This work demonstrates the
suitability of PIC technology for quantum control, opening a path towards
scalable quantum information processing based on optically-programmable atomic
systems
Towards a holographic approach to spherical aberration correction in scanning transmission electron microscopy
Recent progress in phase modulation using nanofabricated electron holograms has demonstrated how the phase of an electron beam can be controlled. In this paper, we apply this concept to the correction of spherical aberration in a scanning transmission electron microscope and demonstrate an improvement in spatial resolution. Such a holographic approach to spherical aberration correction is advantageous for its simplicity and cost-effiectiveness