Wideband wavelength conversion using double-pass cascaded χ:χ interaction in lossy waveguides

We report the wavelength conversion based on double-pass cascaded nonlinear interaction (χ⁽²⁾:χ⁽²⁾) of sum and difference frequency generation in quasi-phase matched lithium niobate waveguides and compare it with double-pass cascaded second harmonic generation and difference frequency generation with and without waveguide loss. It is shown that the efficiency decreases considerably even for the low-loss waveguide compared to the lossless one especially for long waveguides and to achieve the higher efficiency for the same length, the amount of the extra power to compensate the loss increases. Also, an increased detuning of pump wavelength is proposed to flatten the response with a small efficiency penalty. The detuning- and loss-compensating pump powers can be found using the design diagrams in which the criteria for the design of waveguide length and the assignment of pumps power to obtain the desired efficiency, ripple and bandwidth are presented assuming a 75-nm pump wavelength difference.     

Quadripartite entanglement from cascaded χ nonlinear interactions

We theoretically analyze the generation of quadripartite continuous-variable entanglement, with different frequency, by cascaded nonlinear process in a quadruply resonant optical cavity. This process is realized by one optical parametric down-conversion operated below threshold cascaded by two sum-frequency generations in a quasiperiodic optical supperlattice. It shows that the signal, idler and two sum frequency modes are entangled according to the sufficient inseparability criterion proposed by van Loock and Furusawa. The quantum correlation spectra among these four modes versus normalized analysis frequency and nonlinear coupling coefficients are discussed as well in detail.     

Measurement of the branching ratios for the decays J/ψ → ϱπ and J/ψ → γη′

Decays of the J/ψ (3.1) resonance into final states with two charged hadrons and two photons are investigated. Branching ratios for the decays J/ψ → ?π and J/ψ → γη′ are determined to be

$\text{Г(J/ψ → pφ)}\text{Г(J/ψ → all)}\text{= (1.0± 0.2) ·10}{}^{\mathrm{?2}}\text{,}\text{Г(J/ψ → γη′)}\text{ГJ/ψ → all)}\text{= (2.0± 0.7) ·}{}^{\mathrm{?3}}$

Upper limits for the same decay modes of ψ′ (3.7) are also determined.     

χ measurement and optical limiting studies of urea picrate

The molecular charge complex urea picrate (UP) was synthesized and its third order nonlinear optical properties have been investigated using a single beam Z-scan technique with nanosecond laser pulses at 532 nm. Open aperture data of the compound indicates two photon absorption at this wavelength. The nonlinear refractive index n₂, nonlinear absorption coefficient β, magnitude of effective third order susceptibility χ⁽³⁾, the second order hyperpolarizability γ_h and the coupling factor ρ have been estimated. The experimentally determined values of β, n₂, Re χ⁽³⁾ and Im χ⁽³⁾, γ_h and ρ of the compound UP are 2.146 cm/GW, −1.258×10⁻¹¹ esu, −1.347×10⁻¹³ esu, 0.377×10⁻¹³ esu, 0.69×10⁻³² esu and 0.28, respectively. The compound exhibits good optical limiting at 532 nm with the limiting threshold of 80 μJ/pulse. Our studies suggest that compound UP is a potential candidate for optical device applications such as optical limiters.     

μ–τ symmetry in Zee–Babu model

We study the Zee–Babu two-loop neutrino mass generation model and look for a possible flavor symmetry behind the tri-bimaximal neutrino mixing. We find that there probably exists the μ–τ   symmetry in the case of the normal neutrino mass hierarchy, whereas there may not be in the inverted hierarchy case. We also propose a specific model based on a Froggatt–Nielsen-like Z₅$Z_5$ symmetry to naturally accomplish the μ–τ symmetry on the neutrino mass matrix for the normal hierarchy case.     

Second-order optical nonlinearities from χ gratings induced by holographic all-optical poling

The paper presents the second-order optical nonlinearities from χ⁽²⁾ gratings induced by holographic all-optical poling for azobenzene polymer. Second harmonic (SH) signal along the directions with two different vectors was measured. One is strong SH signal diffracted in the same direction as 2ω writing beam with wave vector k_2ω and the other is weak SH signal diffracted in the direction of wave vector of 4k_ω - k_2ω + Δk where k_ω is wave vector of ω beam and Δk is the wave vector mismatch whose vector is parallel to k_ω. The latter signal was used as a tool to monitor the formation of holographic χ⁽²⁾ gratings in real-time because it has off-axis wave vector different from both k_ω and k_2ω. The increase of 2ω intensity on poling process led to the large increase of second-order optical nonlinearity. The real-time monitoring showed that it also gave the large relaxation of second-order optical nonlinearity on poling process. The increase of 2ω (532 nm) energy enhanced the increase of local heating, which led to easier alignment of azobenzene chromophore and also larger relaxation of aligned chromophore.     

A correlation between the two ratios γ/χ(0) and |Jm|/TK in Kondo system

Using the approach based on molecular field calculations for resonant level model; a close relationship between the two ratios γ/χ(0) and |J_m|/T_K is obtained. Where γ represents the electronic contribution in the specific heat, χ(0) is the susceptibility at zero temperature, J_m is the molecular field parameter and T_K is the Kondo temperature.     

Inflationary predictions at small γ

This Letter explores single field inflation models with a constant, but arbitrary speed of sound cs$c_s$, obtained by deforming the kinetic energy terms to a Dirac–Born–Infeld form. Allowing cs<1$c_s<1$ provides a simple parametrization of non-Gaussianity. The dependence of inflationary observables on the parameter cs$c_s$ is considered in the leading order slow roll approximation. The results show that in most cases the dependence is actually rather weak for the range of cs$c_s$ allowed by existing bounds on non-Gaussianity.     

Application of the vector ε and ρ extrapolation methods in the acceleration of the Richardson-Lucy algorithm

The vector ε and ρ extrapolation methods are applied in accelerating the convergence of the Richardson-Lucy (R-L) algorithm and its damped version. The theory and implementation are discussed in detail, and relevant numerical results are given, including the cases of noise-free images and images corrupted by the Poisson noise. The results show that the vector ε and ρ extrapolations of 9 orders can speed the convergence quite efficiently, and the ρ(9) method is more powerful than the ε(9) method for noisy degraded images. The extra computation burden due to the extrapolation is limited, and is well paid back by the accelerated convergence. The performances of these two methods are compared with the famous automatic acceleration method. For noise-free degraded images, the vector ε(9) and ρ(9) methods are more stable than the automatic method. For noisy degraded images, the damped R-L algorithm accelerated by vector ρ(9) or automatic methods is more powerful, and the instability of the automatic method is restrained by the damping strategy. We explain the instability of the method in accelerating the normal R-L algorithm by the numerical noise due to its frequent applications in the run.     

Sharper focal spot below λ/4 of azimuthally polarized illumination phase-encoded by the binary 0/π phase plate

The intensity distribution in the focal region for the azimuthally polarized beam phase-encoded by the binary 0/π phase plate is calculated on the basis of the vector diffraction theory. With the annular pupil aperture employed, the resolution of the focal spot will be improved remarkably. We demonstrate a sharper focal spot with full width at half maximum (FWHM) of 0.223λ (below λ/4), significantly smaller that of linear, circular and radial polarization beam under the same condition. The focusing phenomena for illumination beam with various polarization status and beam shapes are analyzed explicitly. This analysis could have potential applications in confocal microscopy and two-photo microscopy for polarization difference imaging.     

Doubly heavy baryon production at γγ collider

The inclusive production of doubly heavy baryons Ξ_cc${\Xi }_{cc}$ and Ξ_bb${\Xi }_{bb}$ at γγ collider is investigated. It is found that the contribution from the heavy quark pair QQ in color triplet and color sextet are important.     

A deformed relativity with the quantum ℏ

Quantum relativity as a generalized, or rather deformed, version of Einstein relativity may offer a new framework to think about the structure of space–time at the true microscopic/quantum level. The approach typically gives some picture of a noncommutative (quantum) space–time. We propose a formulation with two deformations implemented on the Poincaré symmetry, using the independent Planck mass and Planck length as the invariant constraints. Together, they give the quantum ?  . The scheme leads to SO(2,4)$\mathit{SO}(2,4)$ as the relativity symmetry. We present a linear realization on a classical six-geometry beyond the familiar setting of space–time. Two extra coordinates to be considered as neither space nor time are needed. The last deformation step implementing the Planck length invariant constraines the six-geometry, as an extension of 4D space–time, giving it the structure of a AdS hypersurface. The resulted quantum world hence does not admit coordinate translation symmetries, which terminates further extension to an unstable symmetry. The quantum world is shown to be parallel to the “conformal universe”, but not scale invariant.     

Large N flavor β-functions: A recap

β-Functions for abelian and nonabelian gauge theories are studied in the regime where the large N   flavor expansion is applicable. The first nontrivial order in the 1/N$1/N$ expansion is known for any value of Nα, and there are also various indications as to the nature of higher order effects. The singularity structure as a function of Nα has implications for the existence of nontrivial fixed points.