6,629 research outputs found
CW-pumped telecom band polarization entangled photon pair generation in a Sagnac interferometer
A polarization entangled photon pair source is widely used in many quantum
information processing applications such as teleportation, quantum swapping,
quantum computation and high precision quantum metrology. Here, we report on
the generation of a continuous-wave pumped degenerated 1550 nm polarization
entangled photon pair source at telecom wavelength using a type-II
phase-matched periodically poled KTiOPO4 crystal in a Sagnac interferometer.
Hong-Ou-Mandel-type interference measurement shows the photon bandwidth of 2.4
nm. High quality of entanglement is verified by various kinds of measurements,
for example two-photon interference fringes, Bell inequality and quantum states
tomography. The wavelength of photons can be tuned over a broad range by
changing the temperature of crystal or pump power without losing the quality of
entanglement. This source will be useful for building up long-distance quantum
networks
Realization of Zero-Refractive-Index Lens with Ultralow Spherical Aberration
Optical complex materials offer unprecedented opportunity to engineer
fundamental band dispersion which enables novel optoelectronic functionality
and devices. Exploration of photonic Dirac cone at the center of momentum space
has inspired an exceptional characteristic of zero-index, which is similar to
zero effective mass in fermionic Dirac systems. Such all-dielectric zero-index
photonic crystals provide an in-plane mechanism such that the energy of the
propagating waves can be well confined along the chip direction. A
straightforward example is to achieve the anomalous focusing effect without
longitudinal spherical aberration, when the size of zero-index lens is large
enough. Here, we designed and fabricated a prototype of zero-refractive-index
lens by comprising large-area silicon nanopillar array with plane-concave
profile. Near-zero refractive index was quantitatively measured near 1.55 um
through anomalous focusing effect, predictable by effective medium theory. The
zero-index lens was also demonstrated to perform ultralow longitudinal
spherical aberration. Such IC compatible device provides a new route to
integrate all-silicon zero-index materials into optical communication, sensing,
and modulation, and to study fundamental physics on the emergent fields of
topological photonics and valley photonics.Comment: 14 pages, 4 figure
A Transmissive X-ray Polarimeter Design For Hard X-ray Focusing Telescopes
The X-ray Timing and Polarization (XTP) is a mission concept for a future
space borne X-ray observatory and is currently selected for early phase study.
We present a new design of X-ray polarimeter based on the time projection gas
chamber. The polarimeter, placed above the focal plane, has an additional rear
window that allows hard X-rays to penetrate (a transmission of nearly 80% at 6
keV) through it and reach the detector on the focal plane. Such a design is to
compensate the low detection efficiency of gas detectors, at a low cost of
sensitivity, and can maximize the science return of multilayer hard X-ray
telescopes without the risk of moving focal plane instruments. The sensitivity
in terms of minimum detectable polarization, based on current instrument
configuration, is expected to be 3% for a 1mCrab source given an observing time
of 10^5 s. We present preliminary test results, including photoelectron tracks
and modulation curves, using a test chamber and polarized X-ray sources in the
lab
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