[en] Published in summary form only

No abstract available

[en] We present a theoretical treatment of Bragg scattering of a degenerate Fermi gas in the weakly interacting BCS regime. Our numerical calculations predict correlated scattering of Cooper pairs into a spherical shell in momentum space. The scattered shell of correlated atoms is centered at half the usual Bragg momentum transfer, and can be clearly distinguished from atoms scattered by the usual single-particle Bragg mechanism. We develop an analytic model that explains key features of the correlated-pair Bragg scattering, and determine the dependence of that scattering on the initial pair correlations in the gas

[en] Constant-temperature rooms have been widely used in industrial production, quality testing, and research laboratories. This paper proposes a high-precision tilt sensor suitable for a constant- temperature room, which has achieved a wide-range power change while the fiber Bragg grating (FBG) reflection peak wavelength shifted very little, thereby demonstrating a novel method for obtaining a high-precision tilt sensor. This paper also studies the effect of the reflection peak on measurement precision. The proposed sensor can distinguish the direction of tilt with an excellent sensitivity of 403 dBm/° and a highest achievable resolution of 2.481 × 10"−"5 ° (that is, 0.08% of the measuring range). (paper)

[en] The purpose of this paper is to study the polymer coated FBG sensor characteristics. For this study, FBG sensors coated with Acrylate, sensor coated with Ormocer (polymer) and uncoated FBG sensors were arranged in single fiber using wavelength division multiplexing (WDM) scheme. The sensitivity of the gratings coated with Ormocer and acrylate was found to be about 2.7 and 2.3 times greater than that of the bare FBG at low temperature. Also, the sensor array was found to be highly stable and shows good repeatability and reproducibility after 200 thermal cycling. The time response of the Ormocer coated sensor which was protected by a 1.6mm diameter stainless steel capillary tube was found to be nearly 12 sec. Expanded uncertainty of Ormocer coated sensor has been estimated to be 0.13 K at 77 K. (author)

[en] Published in summary form only

[en] Short communication

[en] Interrogating multiple fiber Bragg gratings (FBG) requires highly sensitive spectrum scanning equipment such as optical spectrum analyzers, tunable filters, acousto-optic tunable filters etc, which are expensive, bulky and time consuming. In this paper, we present a new approach for multiple FBG sensor interrogation using long-period gratings and an artificial neural network. The reflection spectra of the multiplexed FBGs are modulated by two long period gratings separately and the modulated optical intensities were detected by two photodetectors. The outputs of the detectors are then used as input in a previously trained artificial neural network to interrogate the FBG sensors. Simulations have been performed to determine the strain and wavelength shift using two and four sensors. The interrogation system has also been demonstrated experimentally for two sensors using simply supported beams in the range of 0–350 μstrain. The proposed interrogation scheme has been found to identify the perturbed FBG, and to determine strain and wavelength shift with reasonable accuracy. (paper)

No abstract available

[en] A unified semiclassical treatment of Bragg scattering from Bose-Einstein condensates is presented. The formalism is based on Gross-Pitaevskii equations driven by a classical light field, and leads to a single-component equation incorporating the effects of mean-field nonlinearity and spatial inhomogeneity. Three-dimensional numerical simulations of this equation in cylindrical symmetry are used to investigate Bragg scattering for a number of cases. Scattering from a condensate released from a trap produces characteristic cycling of the atomic momentum, and an analytic description is given using a linear model incorporating spatial non-uniformity. Simple expressions obtained for the momentum packet cycling are shown to accurately describe the full nonlinear behaviour within a well specified validity range and a transition linewidth is derived. For the case of a trapped condensate, a numerical study of momentum spectroscopy is carried out and the shift of the Bragg resonance condition due to mean-field nonlinearity is investigated. (author)