Interference (wave propagation)

About: Interference (wave propagation) is a research topic. Over the lifetime, 26086 publications have been published within this topic receiving 321110 citations.

Measurement of the Amplitude and Phase of a Sculpted Rydberg Wave Packet

Abstract: We have completely determined the amplitude and phase of a quantum wave packet. The wave packet was shaped using a programmable optical pulse. Phase information comes from analysis of covariant fluctuations due to interference between the wave packet and a well-characterized reference.

Interference phenomenon in optical transition radiation and its application to particle beam diagnostics and multiple‐scattering measurements

Abstract: The optical transition radiation emitted by electron‐irradiated aluminum, silver, gold‐coated plates, and self‐supported aluminum and Mylar films has been investigated experimentally. The investigation was made with an electron beam incident at 45 °, having a mean intensity of 1 μA, and an energy which was varied from 35 up to 72 MeV (68.5<γ<140.9). The study of the angular distribution and degree of polarization has shown that the high‐directivity radiation is emitted around the direction of specular reflection and that the contribution of the optical bremsstrahlung is negligible. When two parallel foils are used, the resulting angular distribution exhibits an oscillating behavior arising from the interference of the fields emitted at both interfaces. This interference phenomenon is strongly related to the so‐called formation zone in a vacuum, introduced by Garibyan. The intensity of light integrated in a small aperture at the center of the interference pattern presents a strong γ dependence (of the form γ8) which was exploited in the optimization of the phase adjustment of the electron bunches in the accelerating sections of the machine. In such a device using the interference phenomena in transition radiation, the possibility of measurements of the beam energy with a precision of about 1% has also been shown. On the basis of the visibility of fringes, the angular spread of the electron beam and the mean‐square scattering angle in a given material were also estimated.

Multimode interference couplers for the conversion and combining of zero- and first-order modes

Abstract: Optical waveguide mode-combiners for fundamental and first-order modes, based on multimode interference (MMI) couplers are presented. These devices convert a fundamental mode into a transversal first-order mode and combine it in lossless fashion with a second fundamental mode. They can separate zero- and first-order modes in a common waveguide and allow the splitting and combining of zero- and first-order modes with nonuniform power splitting ratios. Realizations in InGaAsP-InP are demonstrated. These new components have successfully been integrated into all-optical switches and were found to have advantageous characteristics in all-optical devices.

DS/CDMA successive interference cancellation

Abstract: Conventional DS/CDMA detectors operate by enhancing a desired user while suppressing other users, considered as interference (multiple access interference, MAI) or noise. A different viewpoint is to consider other users not as noise but to jointly detect all users' signals (multiuser detection). This has significant potential of increasing capacity and near/far resistance. Optimal multiuser detection is, however, too complex to implement, thus motivating the search for suboptimal algorithms. Our objective is to underline the need for simplicity and to discuss what is a relatively simple form of multiuser detection (at the base station of a cellular system), successive interference cancellation. The cancellation scheme uses only components already present in a conventional detector. >

Transmit Optimization With Improper Gaussian Signaling for Interference Channels

Abstract: This paper studies the achievable rates of Gaussian interference channels with additive white Gaussian noise (AWGN), when improper or circularly asymmetric complex Gaussian signaling is applied. For the Gaussian multiple-input multiple-output interference channel (MIMO-IC) with the interference treated as Gaussian noise, we show that the user's achievable rate can be expressed as a summation of the rate achievable by the conventional proper or circularly symmetric complex Gaussian signaling in terms of the users' transmit covariance matrices, and an additional term, which is a function of both the users' transmit covariance and pseudo-covariance matrices. The additional degrees of freedom in the pseudo-covariance matrix, which is conventionally set to be zero for the case of proper Gaussian signaling, provide an opportunity to further improve the achievable rates of Gaussian MIMO-ICs by employing improper Gaussian signaling. To this end, this paper proposes widely linear precoding, which efficiently maps proper information-bearing signals to improper transmitted signals at each transmitter for any given pair of transmit covariance and pseudo-covariance matrices. In particular, for the case of two-user Gaussian single-input single-output interference channel (SISO-IC), we propose a joint covariance and pseudo-covariance optimization algorithm with improper Gaussian signaling to achieve the Pareto-optimal rates. By utilizing the separable structure of the achievable rate expression, an alternative algorithm with separate covariance and pseudo-covariance optimization is also proposed, which guarantees the rate improvement over conventional proper Gaussian signaling.