1,910,984 research outputs found
Demixing light paths inside disordered metamaterials
We experimentally demonstrate the first method to focus light inside disordered photonic metamaterials. In such materials, scattering prevents light from forming a geometric focus. Instead of geometric optics, we used multi-path interference to make the scattering process itself concentrate light on a fluorescent nanoscale probe at the target position. Our method uses the fact that the disorder in a solid material is fixed in time. Therefore, even disordered light scattering is deterministic. Measurements of the probes fluorescence provided the information needed to construct a specific linear combination of hundreds of incident waves, which interfere constructively at the probe.\ud
\u
Amplitude and phase evolution of optical fields inside periodic photonic structures
Optical amplitude distributions of light inside periodic photonic structures are visualized with subwavelength resolution. In addition, using a phase-sensitive photon scanning tunneling microscope, we simultaneously map the phase evolution of light. Two different structures, which consist of a ridge wave-guide containing periodic arrays of nanometer scale features, are investigated. We determine the wavelength dependence of the exponential decay rate inside the periodic arrays. Furthermore, various interference patterns are observed, which we interpret as interference between light reflected by the substrate and light inside the waveguide. The phase information obtained reveals scattering phenomena around the periodic array, which gives rise to phase jumps and phase singularities. Locally around the air rods, we observe an unexpected change in effective refractive index, a possible indication for anomalous dispersion resulting from the periodicity of the array
Comment on "Observation of a push force on the end face of a nanometer silica filament exerted by outgoing light," Phys. Rev. Lett. 101, 243601 (2008)
In a recent paper, W. She, J. Yu and R. Feng reported the slight deformations
observed upon transmission of a light pulse through a fairly short length of a
silica glass nano-fiber. Relating the shape and magnitude of these deformations
to the momentum of the light pulse both inside and outside the fiber, these
authors concluded that, within the fiber, the photons carry the Abraham
momentum. In my view, the authors' claim that they have resolved the
Abraham-Minkowski controversy surrounding the momentum of photons inside
dielectric media is premature. A correct interpretation of the experiments of
She et al requires precise calculations that would properly account not only
for the electromagnetic momentum (both inside and outside the fiber) but also
for the Lorentz force exerted on the fiber by the light pulse in its entire
path through this nano-waveguide.Comment: 2 pages, 4 reference
Control of energy density inside disordered medium by coupling to open or closed channels
We demonstrate experimentally an efficient control of light intensity
distribution inside a random scattering system. The adaptive wavefront shaping
technique is applied to a silicon waveguide containing scattering
nanostructures, and the on-chip coupling scheme enables access to all input
spatial modes. By selectively coupling the incident light to open or closed
channels of the disordered system, we not only vary the total energy stored
inside the system by 7.4 times, but also change the energy density distribution
from an exponential decay to a linear decay and to a profile peaked near the
center. This work provides an on-chip platform for controlling light-matter
interactions in turbid media
Emergence of atom-light-mirror entanglement inside an optical cavity
We propose a scheme for the realization of a hybrid, strongly
quantum-correlated system formed of an atomic ensemble surrounded by a
high-finesse optical cavity with a vibrating mirror. We show that the steady
state of the system shows tripartite and bipartite continuous variable
entanglement in experimentally accessible parameter regimes, which is robust
against temperature
Fighting against fast speckle decorrelation for light focusing inside live tissue by photon frequency shifting
Light focusing inside live tissue by digital optical phase conjugation (DOPC) has drawn increasing interest due to its potential biomedical applications in optogenetics, microsurgery, phototherapy, and deep-tissue imaging. However, fast physiological motions in a live animal, including blood flow and respiratory motions, produce undesired photon perturbation and thus inevitably deteriorate the performance of light focusing. Here, we develop a photon-frequency-shifting DOPC method to fight against fast physiological motions by switching the states of a guide star at a distinctive frequency. Therefore, the photons tagged by the guide star are well detected at the specific frequency, separating them from the photons perturbed by fast motions. Light focusing was demonstrated in both phantoms in vitro and mice in vivo with substantially improved focusing contrast. This work puts a new perspective on light focusing inside live tissue and promises wide biomedical applications
Hadro-Charmonium
We argue that relatively compact charmonium states, , ,
, can very likely be bound inside light hadronic matter, in particular
inside higher resonances made from light quarks and/or gluons. The charmonium
state in such binding essentially retains its properties, so that the bound
system decays into light mesons and the particular charmonium resonance. Thus
such bound states of a new type, which we call hadro-charmonium, may explain
the properties of some of the recently observed resonant peaks, in particular
of Y(4.26), Y(4.32-4.36), Y(4.66), and Z(4.43). We discuss further possible
implications of the suggested picture for the observed states and existence of
other states of hadro-charmonium and hadro-bottomonium.Comment: 4 pages, RevTe
- âŠ