1,721,161 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Decay of stationary light pulses in ultracold atoms
No full textWe develop a general scheme for studying the optical response of ultracold atoms driven into a regime of standing-wave electromagnetically induced transparency. We rely on full numerical solutions of the Maxwell-Liouville equations without invoking secular and adiabatic approximations and arbitrary initial state assumptions. These approximations and assumptions can conceal, e.g., significant loss and diffusion responsible for the decay of stationary light pulses in cold atomic samples. The complex decay dynamics of a stationary light pulse is here analyzed in terms of higher-order spin and optical coherences that arise from nonlinear interactions of the stationary light pulse with the two counterpropagating components of a standing-wave driving field. Specific results for stationary light pulses in cold (87)Rb atoms have been discussed for temperature regimes where the residual Doppler broadening is negligible
A 400-mu W IoT Low-IF Voltage-Mode Receiver Front-End With Charge-Sharing Complex Filter
No full textThis work reports on a low-intermediate frequency (IF) voltage-mode receiver front-end for Internet-of-Things (IoT) applications. Design and noise analysis of an unbalanced gate-boosted common-gate low-noise amplifier (LNA) is presented, showing 50% lower power dissipation compared with the conventional balanced topology. Improved linearity is achieved thanks to channel-selection, consisting of two complex poles centered at 2 MHz IF. The first complex pole is embedded in the passive down-conversion mixer for improved frequency selectivity in front of the baseband voltage amplifier. Built in a 28-nm CMOS process, the proposed front-end occupies an active area of 0.175 mm(2), it is supplied with 1 V and consumes only 400 mu W, while showing a minimum noise figure (NF) of 6.8 dB and an out-of-band (OOB) IIP3 of -0.35 dBm. The performance meets Bluetooth low-energy (BLE) requirements and is competitive with other sub-mW receivers
Controlled light-pulse propagation in driven color centers in diamond
No full textInhomogeneously broadened optical transitions of nitrogen-vacancy centers in diamond may be employed to attain fully developed photonic band-gap structures with negligible absorption via coherent optical nonlinearities. For realistic material parameters, the resulting band gap may be tuned via the coupling field to acquire reflectivities very close to unity and sufficiently large bandwidths. We anticipate that this can be used to optically control with remarkable experimental simplicity the reflected and transmitted parts of an incident light pulse
All-Optical Light Confinement in Dynamic Cavities in Cold Atoms
No full textWe show how to realize in a cold atomic sample a dynamic magneto-optically controlled cavity in which a slow-light pulse can be confined and released on demand. The probe optical pulse is retrieved from the atomic spin coherence initially stored within the cavity and is subsequently confined there subject to a slow-light regime with little loss and diffusion for time intervals as long as a few hundred microseconds before being extracted from either side of the cavity. Our proof-of-principle scheme illustrates the underlying physics of this new mechanism for coherent light confinement and manipulation in cold atoms. This may ease the realization of nonlinear interactions between weak light pulses where strong atom-photon interactions are required for quantum information processing
Stationary light pulses in cold thermal atomic clouds
No full textFourier-expanded Maxwell-Liouville equations are employed to study the light pulse dynamics in atomic samples coherently driven by a standing-wave light field. Solutions are obtained by a suitable truncation of the Maxwell-Liouville equations that contain the number of spin and optical Fourier coherence components appropriate to the sample temperature. This approach is examined here for cold but thermal atoms where the Doppler broadening is still not negligible and familiar secular approximations no longer hold. In this temperature regime higher-order momentum Fourier coherence components are shown to be important for achieving excellent agreement with a recent experiment done in cold (87)Rb clouds at several hundred microkelvins
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