2,334 research outputs found
Amplification of Angular Rotations Using Weak Measurements
We present a weak measurement protocol that permits a sensitive estimation of
angular rotations based on the concept of weak-value amplification. The shift
in the state of a pointer, in both angular position and the conjugate orbital
angular momentum bases, is used to estimate angular rotations. This is done by
an amplification of both the real and imaginary parts of the weak-value of a
polarization operator that has been coupled to the pointer, which is a spatial
mode, via a spin-orbit coupling. Our experiment demonstrates the first
realization of weak-value amplification in the azimuthal degree of freedom. We
have achieved effective amplification factors as large as 100, providing a
sensitivity that is on par with more complicated methods that employ quantum
states of light or extremely large values of orbital angular momentum.Comment: 5 pages, 3 figures, contains supplementary informatio
Experimental generation of an optical field with arbitrary spatial coherence properties
We describe an experimental technique to generate a quasi-monochromatic field
with any arbitrary spatial coherence properties that can be described by the
cross-spectral density function, . This is done by using a
dynamic binary amplitude grating generated by a digital micromirror device
(DMD) to rapidly alternate between a set of coherent fields, creating an
incoherent mix of modes that represent the coherent mode decomposition of the
desired . This method was then demonstrated experimentally
by interfering two plane waves and then spatially varying the coherent between
these two modes such that the interference fringe visibility was shown to vary
spatially between the two beams in an arbitrary and prescribed way.Comment: 6 pages, 5 figur
Bacterial contamination of table eggs and the influence of housing systems
With the introduction of alternative housing systems for laying hens in the EU, recent research has focussed on the bacterial contamination of table eggs, e.g. eggshell and egg content contamination. Contamination of eggshells with aerobic bacteria is generally higher for nest eggs from non-cage systems compared to nest eggs from furnished cages or eggs from conventional cages. Studies indicate limited or no systematic differences in eggshell contamination with aerobic bacteria between eggs laid in the nest boxes of furnished cages and eggs laid in conventional cages. The major differences found in experimental studies between cage- and non-cage systems are less pronounced under commercial conditions. The effect of housing system on eggshell contamination with specific groups of bacteria is variable. Limited information is available on the influence of housing system on egg content contamination. Recent research does not indicate large differences in egg content contamination between eggs from cage- and non-cage systems (ignoring outside nest and floor eggs). The microflora of the eggshell is dominated by Gram-positive bacteria, whereas Gram-negative bacteria are best equipped to overcome the antimicrobial defences of the egg content. Much of the research on eggshell and egg content contamination focuses on Salmonella, since infection with Salmonella enteritidis, resulting from the consumption of contaminated eggs or egg products, is still a major health problem. Observed Salmonella prevalence on the eggshell and in the egg content vary, depending on the fact whether investigations were based on randomly sampled table eggs or on eggs from naturally infected hens. The limited information available on other pathogens shows that they are exclusively isolated from the eggshell and not from the internal contents
Multiplexing Free-Space Channels using Twisted Light
We experimentally demonstrate an interferometric protocol for multiplexing
optical states of light, with potential to become a standard element in
free-space communication schemes that utilize light endowed with orbital
angular momentum (OAM). We demonstrate multiplexing for odd and even OAM
superpositions generated using different sources. In addition, our technique
permits one to prepare either coherent superpositions or statistical mixtures
of OAM states. We employ state tomography to study the performance of this
protocol, and we demonstrate fidelities greater than 0.98.Comment: 4 pages, 3 figure
Rapid Generation of Light Beams Carrying Orbital Angular Momentum
We report a technique for encoding both amplitude and phase variations onto a
laser beam using a single digital micro-mirror device (DMD). Using this
technique, we generate Laguerre-Gaussian and vortex orbital-angular-momentum
(OAM) modes, along with modes in a set that is mutually unbiased with respect
to the OAM basis. Additionally, we have demonstrated rapid switching among the
generated modes at a speed of 4 kHz, which is much faster than the speed
regularly achieved by spatial light modulators (SLMs). The dynamic control of
both phase and amplitude of a laser beam is an enabling technology for
classical communication and quantum key distribution (QKD) systems that employ
spatial mode encoding
Influence of Atmospheric Turbulence on Optical Communications using Orbital Angular Momentum for Encoding
We describe an experimental implementation of a free-space 11-dimensional
communication system using orbital angular momentum (OAM) modes. This system
has a maximum measured OAM channel capacity of 2.12 bits/photon. The effects of
Kolmogorov thin-phase turbulence on the OAM channel capacity are quantified. We
find that increasing the turbulence leads to a degradation of the channel
capacity. We are able to mitigate the effects of turbulence by increasing the
spacing between detected OAM modes. This study has implications for
high-dimensional quantum key distribution (QKD) systems. We describe the sort
of QKD system that could be built using our current technology.Comment: 6 pages, 5 figure
Free-space communication through turbulence: a comparison of plane-wave and orbital-angular-momentum encodings
Free-space communication allows one to use spatial mode encoding, which is
susceptible to the effects of diffraction and turbulence. Here, we discuss the
optimum communication modes of a system while taking such effects into account.
We construct a free-space communication system that encodes information onto
the plane-wave (PW) modes of light. We study the performance of this system in
the presence of atmospheric turbulence, and compare it with previous results
for a system employing orbital-angular-momentum (OAM) encoding. We are able to
show that the PW basis is the preferred basis set for communication through
atmospheric turbulence for a large Fresnel number system. This study has
important implications for high-dimensional quantum key distribution systems
Optical ptychography with extended depth of field
Ptychography is an increasingly popular phase imaging technique. However, like any imaging technique it has a depth of field that limits the volume of a thick specimen that can be imaged in focus. Here, we have proposed to extend the depth of field using a multislice calculation model; an optical experiment successfully demonstrates our proposal
Simulating thick atmospheric turbulence in the lab with application to orbital angular momentum communication
We describe a procedure by which a long () optical
path through atmospheric turbulence can be experimentally simulated in a
controlled fashion and scaled down to distances easily accessible in a
laboratory setting. This procedure is then used to simulate a 1-km-long
free-space communication link in which information is encoded in orbital
angular momentum (OAM) spatial modes. We also demonstrate that standard
adaptive optics methods can be used to mitigate many of the effects of thick
atmospheric turbulence.Comment: Rewritten abstract and introductory section to emphasize the
importance of the work and to make it accessible to a more general audience.
Section 2 was expanded to include some background on the physics of
turbulence to allow the paper to be self-contained and understood by
nonspecialist
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