A comparison of high-order time integrators for thermal convection in rotating spherical shells

A numerical study of several time integration methods for solving the three-dimensional Boussinesq thermal convection equations in rotating spherical shells is presented. Implicit and semi-implicit time integration techniques based on backward differentiation and extrapolation formulae are considered. The use of Krylov techniques allows the implicit treatment of the Coriolis term with low storage requirements. The codes are validated with a known benchmark, and their efficiency is studied. The results show that the use of high-order methods, especially those with time step and order control, increase the efficiency of the time integration, and allows to obtain more accurate solutions.     

Optical decoherence and persistent spectral hole burning in Er:LiNbO3

Developing new resonant optical materials for spatial-spectral holography and quantum information applications requires detailed knowledge of the decoherence and population relaxation dynamics for the quantum states involved in the optical transitions, motivating the need for fundamental material studies. We report recent progress in studying these properties in erbium-doped lithium niobate at liquid helium temperatures. The influence of temperature, applied magnetic fields, measurement timescale, and dopant concentration were probed using photon echo spectroscopy and time-resolved spectral hole burning on the 1532 nm transition of Er³⁺:LiNbO₃. Effects of spectral diffusion due to interactions between Er³⁺ ions and between the Er³⁺ ion and ⁷Li and ⁹³Nb nuclear spins in the host lattice were observed. In addition, long-lived persistent spectral storage of seconds to minutes was observed due to non-equilibrium population redistribution among superhyperfine states.     

Line shape in far wings and water vapor absorption in a broad temperature interval

Despite the long-term history of extensive studies on water vapor continuum absorption it can hardly be said that an exhaustive consideration has been given to this problem both from experimental and theoretical viewpoints. For instance, deficiency remains concerning the precise data on the absorption coefficient as a function of temperature, especially at reduced temperatures. New experimental data on water vapor continuum absorption in the 800-1250 cm⁻¹ spectral region at temperatures from 311 to 363 K have become available quite recently [15]. Two advanced variants of the line wing theory - asymptotic and quasistatic - are briefly outlined. The asymptotic line wing theory has been used successfully to describe the absorption coefficient both at elevated temperatures of the Baranov study and at the temperatures of earlier experimental data. Comparison is made with the results obtained from the quasistatic line wing theory.     

GOSAT-2009 methane spectral line list in the 5550-6236 cm range

A methane spectral line list for the 5550-6236 cm⁻¹ range with the intensity cut off 4×10⁻²⁶ cm/molecule at 296 K is presented. The line list is based on new extensive measurements of methane spectral line parameters performed at different temperatures and pressures of methane and buffer gases N₂, O₂ and air. This spectral line list is prepared in HITRAN-2008 format and contains the following spectral line parameters of about 11,000 lines: position, intensity, energy for lower state (where possible), air-broadening and air-shifting coefficients, exponent of temperature dependence of air-broadening coefficient and self-broadening coefficient.     

An analytical study on absorptive lineshape of a driven N-type open four-level system: Quantum interference effects

An open four-level system of having two pairs of closely spaced levels (N-type configuration) is driven by a single electromagnetic field and tuned resonant with the average frequency of four dipole allowed transitions. Under the Doppler free condition and by using a semiclassical formulation of atom-field interaction for four dipole allowed transitions, we derive the optical Bloch equations for the said four-level system coupled to the driving field. In order to obtain the field induced polarization and hence the absorptive lineshapes, we use the usual perturbation method for getting the approximate analytical solution to the coupled optical Bloch equations for the density matrix elements. Through the off-diagonal complex density matrix elements, we introduce the field dependent phase angles arising out of the quantum interference between the levels participating in dipole allowed transitions. The difference between the field dependent and field independent phases are pointed out. In particular, we investigate the effects of Rabi frequencies and the field dependent phases on the absorptive lineshape. The analytical expressions for the effective linewidths, effective detunings and the induced polarization clearly indicate the role of quantum interference.     

Distributed strain measurement using a tellurite glass fiber with Brillouin optical correlation-domain reflectometry

A tellurite glass fiber with a high Brillouin gain was employed for distributed strain measurement with Brillouin optical correlation-domain reflectometry (BOCDR). First, the spatial resolution of BOCDR was evaluated using the tellurite fiber. With the high Brillouin gain of the fiber, it was confirmed clearly in the experiment that the spatial resolution is limited by the Rayleigh scattering-induced noise. Then, the dependence of the Brillouin frequency shift (BFS) on strain in the tellurite fiber was investigated, showing a negative dependence with a coefficient of −0.023 MHz/με. Using this tellurite fiber, the distribution of the BFS around a 1-cm strain-applied section was successfully measured with BOCDR of a nominal spatial resolution of 6 mm.     

Comment on “A special attack on the multiparty quantum secret sharing of secure direct communication using single photons”

In this comment, we show that the special attack [S.-J. Qin, F. Gao, Q.-Y. Wen, F.-C. Zhu, Opt. Commun. 281 (2008) 5472.], which claims to be able to obtain all the transmitted secret message bit values of the protocol of the multiparty quantum secret sharing of secure direct communication using single photons with random phase shift operations, fails. Furthermore, a class of similar attacks are also shown to fail to extract the secrete message.     

Phase response of omnidirectional reflection one-dimensional photonic crystals and defect modes

In this paper, we investigate the phase properties of light reflected from one-dimensional omnidirectional reflection photonic crystal. We observe that the phase changes drastically at large incident angles. This asymmetrical phase change should be considered at oblique incidence, and various phase compensators and retarders can be designed by this nonlinear curved surface of phase shift. Furthermore, for the coupled defect 1D PC, the phase change depends mainly on the top of the sharp peak of the weak undulation within the rectangular defect band, because the top of the peak of the undulation is very sharp, i.e. large phase change look like within almost a single frequency. This drastic phase change can be used to design phase controllers.     

Analysis of athermalizing performance of thermal infrared optical system with Cassegrain antenna

The thermal infrared imaging system is of greatest importance in modern optics and the image quality closely relies on the accuracy of the optical system. Heat-induced mirror deformation influences the transmission performance of the optical antenna system significantly, which further degrades the accuracy of the whole system. In this work, the simulation on lens deformation circumstances under the thermal environment is carried out using the finite-element analysis software ANSYS. The focus shift property caused by the thermal effect is studied in the cases of reflective and refractive Cassegrain optical antennas, and the athermalizing performance of Cassegrain optical antenna system is also concluded. This work presents a direction to accurate designing of the thermal infrared optical system.     

Resolvent and spectral measure on non-trapping asymptotically hyperbolic manifolds III: Global-in-time Strichartz estimates without lossRésolvante et mesure spectrale sur des variétés non-captives asymptotiquement hyperboliques III : Estimations de Strichartz sans perte et globales en temps

In the present paper, we investigate global-in-time Strichartz estimates without loss on non-trapping asymptotically hyperbolic manifolds. Due to the hyperbolic nature of such manifolds, the set of admissible pairs for Strichartz estimates is much larger than usual. These results generalize the works on hyperbolic space due to Anker–Pierfelice and Ionescu–Staffilani. However, our approach is to employ the spectral measure estimates, obtained in the author's joint work with Hassell, to establish the dispersive estimates for truncated/microlocalized Schrödinger propagators as well as the corresponding energy estimates. Compared with hyperbolic space, the crucial point here is to cope with the conjugate points on the manifold. Additionally, these Strichartz estimates are applied to the $L^2$ well-posedness and $L^2$ scattering for nonlinear Schrödinger equations with power-like nonlinearity and small Cauchy data.