Topic
Optical polarization
About: Optical polarization is a research topic. Over the lifetime, 13992 publications have been published within this topic receiving 244284 citations.
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TL;DR: In this paper, the first optical linear polarization measurement for the magnificent seven (M7) was obtained with the Very Large Telescope (VLST) for the first ever for one of the M7.
Abstract: The ‘Magnificent Seven’ (M7) are a group of radio-quiet isolated neutron stars discovered in the soft X-rays through their purely thermal surface emission Owing to the large inferred magnetic fields (B ≈ 1013 G), radiation from these sources is expected to be substantially polarized, independently of the mechanism actually responsible for the thermal emission A large observed polarization degree (PD) is, however, expected only if quantum-electrodynamic (QED) polarization effects are present in the magnetized vacuum around the star The detection of a strong linearly polarized signal would therefore provide the first observational evidence of QED effects in the strong-field regime While polarization measurements in the soft X-rays are not feasible yet, optical polarization measurements are within reach also for quite faint targets, like the M7 which have optical counterparts with magnitudes ≈26–28 Here, we report on the measurement of optical linear polarization for the prototype, and brightest member, of the class, RX J18565−3754 (V ∼ 255), the first ever for one of the M7, obtained with the Very Large Telescope We measured a PD = 1643 ± 526 per cent and a polarization position angle PA = 145°39 ± 9°44, computed east of the North Celestial Meridian The PD that we derive is large enough to support the presence of vacuum birefringence, as predicted by QED
153 citations
TL;DR: The experimental results match well with theory, showing that the transversal filter is a competitive solution to implement advanced adaptive RF filters with broad operational bandwidth, high frequency selectivity, high reconfigurability, and potentially reduced cost and footprint.
Abstract: We demonstrate a photonic radio frequency (RF) transversal filter based on an integrated optical micro-comb source featuring a record low free spectral range of 49 GHz, yielding 80 micro-comb lines across the C -band. This record high number of taps, or wavelengths for the transversal filter results in significantly increased performance including a Q RF factor more than four times higher than previous results. Furthermore, by employing both positive and negative taps, an improved out-of-band rejection of up to 48.9 dB is demonstrated using a Gaussian apodization, together with a tunable center frequency covering the RF spectra range, with a widely tunable 3-dB bandwidth and versatile dynamically adjustable filter shapes. Our experimental results match well with theory, showing that our transversal filter is a competitive solution to implement advanced adaptive RF filters with broad operational bandwidth, high frequency selectivity, high reconfigurability, and potentially reduced cost and footprint. This approach is promising for applications in modern radar and communications systems.
152 citations
TL;DR: In this paper, the authors report the first demonstration of a long-distance ultra-stable frequency dissemination in the microwave range, using an 86-km urban optical link with a fractional frequency instability of 1.3×10−15 at 1-s integration time and below 10−18 at one day.
Abstract: We report the first demonstration of a long-distance ultra-stable frequency dissemination in the microwave range. A 9.15-GHz signal is transferred through an 86-km urban optical link with a fractional frequency instability of 1.3×10−15 at 1-s integration time and below 10−18 at one day. The optical link phase noise compensation is performed with a round-trip method. To achieve such a result we implement light polarisation scrambling and dispersion compensation. This link outperforms all the previous radio-frequency links and compares well with recently demonstrated full optical links.
152 citations
TL;DR: In this article, the probability density functions and lower-order moments of the four Stokes parameters are obtained as a function of the degree of polarization and the mean intensities of the two field components.
Abstract: The probability-density functions and lower-order moments of the four Stokes parameters are obtained as a function of the degree of polarization and the mean intensities of the two field components.
152 citations
TL;DR: In this paper, the fabrication of thin GaAs quantum wires (120-200 A)×(200-300 A) by a novel metal-organic chemical-vapordeposition growth technique is reported.
Abstract: Successful fabrication of thin GaAs quantum wires (120–200 A)×(200–300 A) by a novel metal‐organic chemical‐vapor‐deposition growth technique is reported. The GaAs quantum wires were grown on a V groove formed by two GaAs triangular prisms which were selectively grown on SiO2 masked substrates. The V groove has a very sharp corner at the bottom, which results in reduction of the effective width of the quantum wire structures. The measurement of photoluminescence and photoluminescence excitation spectra with polarization dependence indicate the existence of the quantized state in the quantum wires.
151 citations