Dynamical phase diagram of parity-time symmetry with competing saturable channels

Nonlinear channels play a critical role in realizing dynamical functions. Neural ionic channels and non-volatile memristors each derive representative biological and electrical functionalities, such as repetitive firing or pinched hysteresis. In electromagnetics, saturable channels of amplification or absorption provide a large nonlinearity for nonequilibrium wave dynamics, from conventional lasing to mode locking to recent achievements of the non-reciprocity in complex potentials. Here, we investigate the dynamical phase diagram of parity-time symmetric systems, governed by competing nonlinear channels of saturable amplification and absorption. Determined by the relative strength and saturation level of the channels, three distinctive phases of fast- and slow-response equilibriums, and an oscillating nonequilibrium are demonstrated. On phase boundaries, we also reveal the chaotic existence of the strong oscillation state, which allows the non-reciprocal realization of repetitive resonator firing with fully tunable time delays. This work will promote the wave-based realization of nonlinear and chaotic temporal functions, toward light-based neural systems

Transverse spinning of light with globally unique handedness

Access to the transverse spin of light has unlocked new regimes in topological photonics and optomechanics. To achieve the transverse spin of nonzero longitudinal fields, various platforms that derive transversely confined waves based on focusing, interference, or evanescent waves have been suggested. Nonetheless, because of the transverse confinement inherently accompanying sign reversal of the field derivative, the resulting transverse spin handedness experiences spatial inversion, which leads to a mismatch between the densities of the wavefunction and its spin component and hinders the global observation of the transverse spin. Here, we reveal a globally pure transverse spin in which the wavefunction density signifies the spin distribution, by employing inverse molding of the eigenmode in the spin basis. Starting from the target spin profile, we analytically obtain the potential landscape and then show that the elliptic-hyperbolic transition around the epsilon-near-zero permittivity allows for the global conservation of transverse spin handedness across the topological interface between anisotropic metamaterials. Extending to the non-Hermitian regime, we also develop annihilated transverse spin modes to cover the entire Poincare sphere of the meridional plane. Our results enable the complete transfer of optical energy to transverse spinning motions and realize the classical analogy of 3-dimensional quantum spin states

Progress toward high-Q perfect absorption: A Fano antilaser

Here we propose a route to the high-Q perfect absorption of light by introducing the concept of a Fano anti-laser. Based on the drastic spectral variation of the optical phase in a Fano-resonant system, a spectral singularity for scatter-free perfect absorption can be achieved with an order of magnitude smaller material loss. By applying temporal coupled mode theory to a Fano-resonant waveguide platform, we reveal that the required material loss and following absorption Q-factor are ultimately determined by the degree of Fano spectral asymmetry. The feasibility of the Fano anti-laser is confirmed using a photonic crystal platform, to demonstrate spatio-spectrally selective heating. Our results utilizing the phase-dependent control of device bandwidths derive a counterintuitive realization of high-Q perfect conversion of light into internal energy, and thus pave the way for a new regime of absorption-based devices, including switches, sensors, thermal imaging, and opto-thermal emitters

Chirality in non-Hermitian photonics

Chirality is ubiquitous from microscopic to macroscopic phenomena in physics and biology, such as fermionic interactions and DNA duplication. In photonics, chirality has traditionally represented differentiated optical responses for right and left circular polarizations. This definition of optical chirality in the polarization domain includes handedness-dependent phase velocities or optical absorption inside chiral media, which enable polarimetry for measuring the material concentration and circular dichroism spectroscopy for sensing biological or chemical enantiomers. Recently, the emerging field of non-Hermitian photonics, which explores exotic phenomena in gain or loss media, has provided a new viewpoint on chirality in photonics that is not restricted to the traditional polarization domain but is extended to other physical quantities such as the orbital angular momentum, propagation direction, and system parameter space. Here, we introduce recent milestones in chiral light-matter interactions in non-Hermitian photonics and show an enhanced degree of design freedom in photonic devices for spin and orbital angular momenta, directionality, and asymmetric modal conversion.Comment: 25 pages, 6 figures, accepted in Current Optics and Photonics as an invited revie

Update on εK\varepsilon_K with lattice QCD inputs

We report updated results for $\varepsilon_K$, the indirect CP violation parameter in neutral kaons, which is evaluated directly from the standard model with lattice QCD inputs. We use lattice QCD inputs to fix $\bar{B}_K$, $|V_{cb}|$, $\xi_0$, $\xi_2$, $|V_{us}|$, and $m_c(m_c)$. Since Lattice 2016, the UTfit group has updated the Wolfenstein parameters in the angle-only-fit method, and the HFLAV group has also updated $|V_{cb}|$. Our results show that the evaluation of $\varepsilon_K$ with exclusive $|V_{cb}|$ (lattice QCD inputs) has $4.0\sigma$ tension with the experimental value, while that with inclusive $|V_{cb}|$ (heavy quark expansion based on OPE and QCD sum rules) shows no tension.Comment: 8 pages, 7 figures, Lattice 2017 proceeding, references update

Metadisorder for designer light in random-walk systems

Disorder plays a critical role in signal transport, by controlling the correlation of systems. In wave physics, disordered potentials suppress wave transport due to their localized eigenstates from random-walk scattering. Although the variation of localization with tunable disorder has been intensively studied as a bridge between ordered and disordered media, the general trend of disorder-enhanced localization has remained unchanged, failing in envisaging the existence of delocalization in highly-disordered potentials. Here, we propose the concept of 'metadisorder': tunable random-walk systems having a designed eigenstate with unnatural localization. We demonstrate that one of the eigenstates in a randomly-coupled system can always be arbitrarily molded, regardless of the degree of disorder, by adjusting the self-energy of each element. Ordered waves are then achieved in highly-disordered systems, including planewaves and globally- collective resonances. We also devise counterintuitive functionalities in disordered systems, such as 'small-world-like' transport from non-Anderson-type localization, phase-conserving disorder, and phase-controlled beam steering

Lithiation and electrophilic substitution of dimethyl triazones

The lithiation and electrophilic substitution of dimethyl triazones is described. Directed lithiation or tin–lithium exchange of dimethyl triazones afforded the corresponding dipole stabilized nucleophiles that were trapped with various electrophiles. Keto-triazone derivatives accessed by acylation of such nucleophiles were readily converted into the corresponding imidazolone heterocycles.National Institutes of Health (U.S.) (National Institute of General Medical Sciences (U.S.) GM074825

Update on B→D∗ℓνB\to D^\ast \ell \nu form factor at zero-recoil using the Oktay-Kronfeld action

We present an update on the calculation of $\bar{B}\to D^\ast \ell \bar{\nu}$ semileptonic form factor at zero recoil using the Oktay-Kronfeld bottom and charm quarks on $N_f=2+1+1$ flavor HISQ ensembles generated by the MILC collaboration. Preliminary results are given for two ensembles with $a\approx 0.12$ and $0.09$ fm and $M_\pi\approx 310$ MeV. Calculations have been done with a number of valence quark masses, and the dependence of the form factor on them is investigated on the $a\approx 0.12$ fm ensemble. The excited state is controlled by using multistate fits to the three-point correlators measured at 4--6 source-sink separations.Comment: 7 pages and 4 figures. Talk at The 36th Annual International Symposium on Lattice Field Theory - LATTICE201