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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,711 records · Page 95
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

ON DISCOVERING ELECTROMAGNETIC EMISSION FROM NEUTRON STAR MERGERS: THE EARLY YEARS OF TWO GRAVITATIONAL WAVE DETECTORS

We present the first simulation addressing the prospects of finding an electromagnetic (EM) counterpart to gravitational wave (GW) detections during the early years of only two advanced detectors. The perils of such a search may have appeared insurmountable when considering the coarse ring-shaped GW localizations spanning thousands of square degrees using time-of-arrival information alone. Leveraging the amplitude and phase information of the predicted GW signal narrows the localization to arcs with a median area of only a few hundred square degrees, thereby making an EM search tractable. Based on the locations and orientations of the two LIGO detectors, we find that the GW sensitivity is limited to only two of the four sky quadrants. Thus, the rates of GW events with two interferometers is only ≈40% of the rate with three interferometers of similar sensitivity. Another important implication of the sky quadrant bias is that EM observatories in North America and Southern Africa would be able to systematically respond to GW triggers several hours sooner than Russia and Chile. Given the larger sky areas and the relative proximity of detected mergers, 1 m class telescopes with very wide-field cameras are well-positioned for the challenge of finding an EM counterpart. Identification of the EM counterpart amidst the larger numbers of false positives further underscores the importance of building a comprehensive catalog of foreground stellar sources, background active galactic nucleus and potential host galaxies in the local universe. This initial study is based on a small sample of 17 detected mergers; future works will expand this sample.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

PROSPECTS FOR JOINT GRAVITATIONAL-WAVE AND ELECTROMAGNETIC OBSERVATIONS OF NEUTRON-STAR-BLACK-HOLE COALESCING BINARIES

Coalescing neutron-star-black-hole (NS-BH) binaries are a promising source of gravitational-wave (GW) signals detectable with large-scale laser interferometers such as the Advanced Laser Interferometer Gravitational-Wave Observatory and Virgo. They are also one of the main short gamma-ray burst (SGRB) progenitor candidates. If the black hole (BH) tidally disrupts its companion, an SGRB may be ignited when a sufficiently massive accretion disk forms around the remnant BH. Detecting an NS-BH coalescence both in the GW and electromagnetic (EM) spectrum offers a wealth of information about the nature of the source. How much can actually be inferred from a joint detection is unclear, however, as a mass/spin degeneracy may reduce the GW measurement accuracy. To shed light on this problem and on the potential of joint EM+GW observations, we here combine recent semi-analytical predictions for the remnant disk mass with estimates of the parameter-space portion that is selected by a GW detection. We identify cases in which an SGRB ignition is supported, others in which it can be excluded, and finally others in which the outcome depends on the chosen model for the currently unknown NS equation of state. We pinpoint a range of systems that would allow us to place lower bounds on the equation of state stiffness if both the GW emission and its EM counterpart are observed. The methods we develop can broaden the scope of existing GW detection and parameter-estimation algorithms and could allow us to disregard about half of the templates in an NS-BH search following an SGRB trigger, increasing its speed and sensitivity.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Magnetic frame-dragging correction to the electromagnetic solution of a compact neutron star

ABSTRACT Neutron stars are usually modelled as spherical, rotating perfect conductors with a predominant intrinsic dipolar magnetic field anchored to their stellar crust. Due to their compactness, General Relativity corrections must be accounted for in Maxwell’s equations, leading to modified interior and exterior electromagnetic solutions. We present analytical solutions for slowly rotating magnetized neutron stars, taking into account the magnetic frame-dragging correction. For typical compactness values, i.e. Rs ∼ 0.5 [R*], we show that the new terms lead to a per cent order correction in the magnetic field orientation and strength compared to the case, with no magnetic frame-dragging correction. Also, we obtain a self-consistent redistribution of the surface azimuthal current. We verify the validity of the derived solution through two-dimensional particle-in-cell simulations of an isolated neutron star. Defining the azimuthal electric and magnetic field amplitudes during the transient phase as observables, we prove that the magnetic frame-dragging correction reduces the transient wave amplitude, as expected from the analytical solution. We show that simulations are more accurate and stable, when we include all first-order terms. The increased accuracy at lower spatiotemporal resolutions translates into a reduction in simulation runtimes.

Torres, R. (ORCID:0000000291820228)↗
DOE OSTI2023

Quantum Langevin theory for two coupled phase-conjugated electromagnetic waves

We provide a general macroscopic phenomenological formula of quantum Langevin equations for two coupled phase-conjugated electromagnetic fields with linear loss (gain) and complex nonlinear coupling coefficient. The macroscopic phenomenological formula is obtained from the coupling matrix to preserve the field commutation relations and correlations, which does not require knowing the microscopic details of light-matter interaction and internal atomic structures. To validate this phenomenological formula, we take spontaneous four-wave mixing in a double-Λ four-level atomic system as an example to numerically confirm that our macroscopic phenomenological result is consistent with that obtained from the microscopic Heisenberg-Langevin theory. We find that a complex-valued nonlinear coupling coefficient can lead to noises even without linear gain or loss. Lastly, we apply the quantum Langevin equations to study the effects of linear gain and loss, complex phase mismatching, as well as complex nonlinear coupling coefficient in entangled photon pair (biphoton) generation, particularly to their temporal quantum correlations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Conservation law for electromagnetic fields in a space-time-varying medium and its implications

We discuss the propagation of electromagnetic waves in a space-time modulated medium, for which neither energy nor momentum remains conserved. We have found a new conservation law when modulation moves at a constant speed v in a traveling-wave fashion. We use this law to study how light is scattered inside such a medium. We consider both the subluminal (v < c) andsuperluminal (v > c) cases and find that they differ considerably in terms of what remains conserved. We show that the total number of photons is conserved in the subluminal case. In contrast, it is the difference between the forward and backward moving photons that remains conserved in the superluminal case. We also study the reciprocity issue for a space-time modulated medium and found that reciprocity holds in all situations. Here, we develop a quantum formulation of our scattering problem and show that the subluminal case is similar to the action of a beam splitter. In the superluminal case, photon pairs can be generated from vacuum in a fashion analogous to the two-mode frequency down-conversion process.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Narrow-linewidth double-resonance optical pumping spectrum due to electromagnetically induced transparency in ladder-type inhomogeneously broadened media

Based on the cesium 6S{sub 1/2}-6P{sub 3/2}-8S{sub 1/2} ladder-type atomic system, double-resonance optical pumping (DROP) spectra including electromagnetically induced transparency (EIT) effects have been investigated with a room-temperature cesium vapor cell. For both cases of the probe and the coupling laser beams passing through the cesium vapor cell with the counter-propagation (CTP) and co-propagation (CP) configurations, the DROP spectra measured in the experiment display explicitly different linewidths. Thanks to the EIT effect, the linewidth of the DROP spectrum is explicitly narrower for the CTP configuration than for the CP configuration. Experimental results agree with the theoretical analysis considering Doppler averaging. Furthermore, when the coupling laser has moderate power, the DROP spectrum for the CTP configuration clearly shows two components: the narrow part due to the EIT effect and the broad part caused by optical pumping (but these two different components are never seen in the CP configuration). Also, the effect of the intensity of the coupling and probe lasers on the DROP spectra is investigated.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2010

Hanle electromagnetically induced transparency and absorption resonances with a Laguerre Gaussian beam

We describe a computational and experimental study on Hanle electromagnetically induced transparency and absorption resonance line shapes with a Laguerre Gaussian (LG) beam. It is seen that the LG beam profile brings about a significant narrowing in the line shape of the Hanle resonance and ground-state Zeeman coherence in comparison to a Gaussian beam. This narrowing is attributed to the azimuthal mode index of the LG field.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2010

Electromagnetically induced transparency and Autler-Townes splitting: Two similar but distinct phenomena in two categories of three-level atomic systems

Electromagnetically induced transparency (EIT) and Autler-Townes (AT) splitting are two phenomena that could be featured in a variety of three-level atomic systems. The considered phenomena, EIT and AT, are similar ''looking'' in the sense that they are both characterized by a reduction in absorption of a weak field in the presence of a stronger field. In this paper, we explicitly set the threshold of separation between EIT and AT splitting in a unified study of four different three-level atomic systems. Two resonances are studied and compared in each case. A comparison of the magnitudes of the resonances reveals two coupling-field regimes and two categories of three-level system.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2010

Tunable electromagnetically induced transparency and absorption with dressed superconducting qubits

Electromagnetically induced transparency and absorption (EIT and EIA) are usually demonstrated using three-level atomic systems. In contrast to the usual case, we theoretically study the EIT and EIA in an equivalent three-level system: a superconducting two-level system (qubit) dressed by a single-mode cavity field. In this equivalent system, we find that both the EIT and the EIA can be tuned by controlling the level-spacing of the superconducting qubit and hence controlling the dressed system. This tunability is due to the dressed relaxation and dephasing rates which vary parametrically with the level-spacing of the original qubit and thus affect the transition properties of the dressed qubit and the susceptibility. These dressed relaxation and dephasing rates characterize the reaction of the dressed qubit to an incident probe field. Using recent experimental data on superconducting qubits (charge, phase, and flux qubits) to demonstrate our approach, we show the possibility of experimentally realizing this proposal.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2010

Influence of laser beam profile on electromagnetically induced absorption

We compared, experimentally and theoretically, Hanle electromagnetically induced absorption (EIA) obtained using Gaussian and {Pi}-shaped laser beams 3 mm in diameter. The study was done by measuring the transmission of a laser locked to the F{sub g}=2{yields}F{sub e}=3 transition at the D{sub 2} line of {sup 87}Rb in a vacuum cell. EIA linewidths obtained for the two laser profiles were significantly different in the range of laser intensities 1-4 mW/cm{sup 2}. EIA with the {Pi}-shaped laser beam has a broad intensity maximum and linewidths larger than those obtained with the Gaussian beam profile. We also studied Hanle EIA by measuring the transmission of selected segments of the entire laser beam by placing a small movable aperture in front of the detector. Waveforms so obtained in Hanle EIA resonances were strongly influenced both by the radial distance of the transmitted segment from the beam center and by the radial profile of the laser beam. We show that outer regions of Gaussian beam, and central regions of the {Pi}-shaped beam generate the narrowest lines. The different behaviors of EIA owing to different beam profiles revealed by both theory and experiment indicate the importance of the radial profile of the laser beam for proper modeling of coherent effects in alkali metal vapors.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2010

Arrayed and checkerboard optical waveguides controlled by the electromagnetically induced transparency

We introduce two models of quasidiscrete optical systems: an array of waveguides doped by four-level N-type atoms, and a nonlinear checkerboard pattern, formed by doping with three-level atoms of the {Lambda}-type. The dopant atoms are driven by external fields, to induce the effect of the electromagnetically induced transparency (EIT). These active systems offer advantages and additional degrees of freedom, in comparison with ordinary passive waveguiding systems. In the array of active waveguides, the driving field may adjust linear and nonlinear propagation regimes for a probe signal. The nonlinear checkerboard system supports the transmission of stable spatial solitons and their 'fuzzy' counterparts, straight or oblique.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Nondegenerate phase-conjugate wave via stored atomic coherence based on electromagnetically induced transparency in solids

A nondegenerate phase-conjugate wave was generated via stored atomic coherence in a Pr{sup 3+}:Y{sub 2}SiO{sub 5} crystal based on the electromagnetically induced transparency effect, and its capability for wave-front reconstruction of phase distortion was demonstrated experimentally. The phase-matching condition during the storage-retrieval process of the phase-conjugate wave was characterized both experimentally and theoretically in detail. Theoretical simulations fit the experimental data very well. Such a scheme of storage and retrieval of the phase-conjugate wave may have potential applications in optical signal processing and information security.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2011

Measurement of absolute transition frequencies of {sup 87}Rb to nS and nD Rydberg states by means of electromagnetically induced transparency

We report the measurement of absolute excitation frequencies of {sup 87}Rb to nS and nD Rydberg states. The Rydberg transition frequencies are obtained by observing electromagnetically induced transparency on a rubidium vapor cell. The accuracy of the measurement of each state is < or approx. 1 MHz, which is achieved by frequency stabilizing the two diode lasers employed for the spectroscopy to a frequency comb and a frequency comb calibrated wavelength meter, respectively. Based on the spectroscopic data we determine the quantum defects of {sup 87}Rb, and compare it with previous measurements on {sup 85}Rb. We determine the ionization frequency from the 5S{sub 1/2}(F=1) ground state of {sup 87}Rb to 1010.029 164 6(3)THz, providing the binding energy of the ground state with an accuracy improved by two orders of magnitude.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2011

Electromagnetically induced transparency in an inhomogeneously broadened {Lambda} transition with multiple excited levels

Electromagnetically induced transparency (EIT) has mainly been modeled for three-level systems. In particular, considerable interest has been dedicated to the {Lambda} configuration, with two ground states and one excited state. However, in the alkali-metal atoms, which are commonly used, the hyperfine interaction in the excited state introduces several levels which simultaneously participate in the scattering process. When the Doppler broadening is comparable with the hyperfine splitting in the upper state, the three-level {Lambda} model does not reproduce the experimental results. Here we theoretically investigate the EIT in a hot vapor of alkali-metal atoms and demonstrate that it can be strongly reduced by the presence of multiple excited levels. Given this model, we also show that well-designed optical pumping enables us to significantly recover the transparency.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Electrometry near a dielectric surface using Rydberg electromagnetically induced transparency

Electrometry near a dielectric surface is performed using Rydberg electromagnetically induced transparency. The large polarizability of high-n-state Rydberg atoms gives this method extreme sensitivity. We show that dipoles produced by adsorbates on the dielectric surface produce a significant electric field that responds to an applied field with a time constant of order 1 s. For transient applied fields (with a time scale of less than 1 s) we observe good agreement with calculations based on numerical solutions of Laplace's equation using an effective dielectric constant to simulate the bulk dielectric.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Polarization dependence of double-resonance optical pumping and electromagnetically induced transparency in the 5S{sub 1/2}-5P{sub 3/2}-5D{sub 5/2} transition of {sup 87}Rb atoms

The polarization dependence of double-resonance optical pumping (DROP) in the ladder-type electromagnetically induced transparency (EIT) of the 5S{sub 1/2}-5P{sub 3/2}-5D{sub 5/2} transition of {sup 87}Rb atoms is studied. The transmittance spectra in the 5S{sub 1/2}(F=2)-5P{sub 3/2}(F'=3)-5D{sub 5/2}(F''=2,3,4) transition were observed as caused by EIT, DROP, and saturation effects in the various polarization combinations between the probe and coupling lasers. The features of the double-structure transmittance spectra in the 5S{sub 1/2}(F=2)-5P{sub 3/2}(F'=3)-5D{sub 5/2}(F''=4) cycling transition were attributed to the difference in saturation effect according to the transition routes between the Zeeman sublevels and the EIT according to the two-photon transition probability.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Electromagnetic near-field interactions of a dipolar emitter with metal and metamaterial nanoslabs

We investigate the emission properties of a polarizable point dipole placed within a subwavelength distance from a silver or a slightly absorbing, negative-index metamaterial nanoslab. Using electromagnetic theory we show that in the immediate vicinity of the slab the dipole-slab interaction prevents the dipole from radiating. For the metamaterial slab close to the perfect-lens arrangement, the interaction is relatively weak and of short range. In particular, a region exists in the near zone of the metamaterial slab where the dipole emission is not disturbed by the interaction, and a bright intensity distribution of subwavelength width is created on the opposite side of the slab. This suggests that a low-loss metamaterial slab can act as a near-field imaging device which does not disturb the object. For the silver slab the interaction is stronger and it reaches over the near-field zone, adversely influencing the imaging capabilities in terms of brightness and resolution. The results are important for the development of metal and metamaterial superlenses.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Robust quantum gates via a photon triggering electromagnetically induced transparency

We propose a scheme to achieve a parallelized controlled-NOT (c-not) gate based on electromagnetically induced transparency (EIT) and cavity-assisted photon scattering. By using the flying photon as the control bit, we can implement a conditional transfer between two logical states of an atom trapped in the cavity with high fidelity and on a microsecond time scale. Thanks to the fact that the photon is well suited for scalable quantum computation, a quantum c-not gate between the single-photon pulses and the nonlocal gate on remote atoms are obtained by reflecting the photon pulse from an optical cavity with a single-trapped atom. Our protocol is robust for spontaneous emission and works quite well in the bad-cavity limit, which makes it more applicable in the laboratory with current experimental techniques.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗