One of the most controversial phenomena in nonlinear dynamics is the recurrence of initial conditions. New optical experiments reveal the origin of this enigma and demonstrate the ability to reconstruct the initial condition of an unstable system.

Observation of Fermi-Pasta-Ulam-Tsingou Recurrence and Its Exact Dynamics

Polymer strategies for high-efficiency and stable perovskite solar cells

As atoms and molecules condense to form solids, a crystalline state can emerge with its highly ordered geometry and subnanometric lattice constant. In some physical systems, such as ferroelectric perovskites, a perfect crystalline structure forms even when the condensing substances are non-stoichiometric. The resulting solids have compositional disorder and complex macroscopic properties, such as giant susceptibilities and non-ergodicity. Here, we observe the spontaneous formation of a cubic structure in composite ferroelectric potassium-lithium-tantalate-niobate with micrometric lattice constant, 10(4) times larger than that of the underlying perovskite lattice. The 3D effect is observed in specifically designed samples in which the substitutional mixture varies periodically along one specific crystal axis. Laser propagation indicates a coherent polarization super-crystal that produces an optical X-ray diffractometry, an ordered mesoscopic state of matter with important implications for critical phenomena and applications in miniaturized 3D optical technologies.

/pdf/super-crystals-in-composite-ferroelectrics-1234d1quxs.pdf

Super-crystals in composite ferroelectrics

Design of photonic crystal based compact all-optical 2 × 1 multiplexer for optical processing devices

Multi-band giant circular dichroism based on conjugated bilayer twisted-semicircle nanostructure at optical frequency

We report the lifetime enhancement of light-induced refractive index grating by applying a bias field during writing. In comparison with the lifetime of about 10 hours of the photorefractive grating prepared without a bias field, the lifetime of the grating with a 4  kV/cm bias field can be prolonged to 7.5 years, which is obtained from the dynamic behavior of grating visualized and monitored with digital holographic microscopy. The higher the bias field is applied, the longer the dark decay time of grating can be achieved. The enhanced lifetime of phase grating is attributed to polar nanoregions oriented by external field. This effect is of great significance for electro-holographic device applications.

Field-induced lifetime enhancement of photorefractive gratings in a Mn:Fe:KTN crystal

High performance ultra-flexible lightweight perovskite photodetectors hold promising applications on arbitrary substrates include unmanned aerial vehicles. Herein, we report a facile method to improve the performance of perovskite photodetectors on flexible ultrathin (50 µm) polyimide substrates by tuning the composition with different ratio of cations. In the presence of lead thiocyanate, certain amount of formamidinium introduction could sufficiently enhance the methylammonium lead triiodide perovskite film quality with prolonged carrier lifetime. Perovskite photodetector with response time of ton=89 ms and toff=47 ms is achieved with a very simple device architecture. In addition, our flexible photodetectors maintain good performances after rigid folding and bending, demonstrating excellent mechanical properties, which can be very useful for a variety of applications.

Improving the performance of ultra-flexible perovskite photodetectors through cation engineering

We measure temperature dependence on Kerr coefficient and quadratic polarized optical coefficient of a paraelectric Mn:Fe:KTN crystal simultaneously in this work, based on digital holographic interferometry (DHI). And the spatial distribution of the field-induced refractive index change can also be visualized and estimated by numerically retrieving sequential phase maps of Mn:Fe:KTN crystal from recording digital holograms in different states. The refractive indices decrease with increasing temperature and quadratic polarized optical coefficient is insensitive to temperature. The experimental results suggest that the DHI method presented here is highly applicable in both visualizing the temporal and spatial behavior of the internal electric field and accurately measuring electro-optic coefficient for electrooptical media.

Temperature dependence of Kerr coefficient and quadratic polarized optical coefficient of a paraelectric Mn:Fe:KTN crystal

Plasmonic chiroptical effects have received more and more attention for their wide application in the fields of plasmonic sensing, biological detection, and analytical chemistry. In this study, we propose a bi-layer semi-ring/rod nanostructure array. The results calculated by the finite element method show that under the exciting of left-handed circularly polarized light and right-handed circularly polarized light, the nanostructure can produce strong multi-band circular dichroism (CD) signal due to the different coupling modes of electric dipole-electric dipole or magnetic dipole-electric dipole. In addition, the CD signal is strongly dependent on the tilt angle θ, the length L of nanorod, the radius R2, and the distance D. In particular, the adjustment of θ can realize the switching of the CD signal between appear and vanish, and the change of L can achieve manipulation only for a particular resonance mode. The results in this study show that the bi-layer semi-ring/rod array nanostructure provides guidance for the generation of CD using plasmonic nanostructures, and it also shows potential application in spectral anti-crosstalk.

https://link.springer.com/content/pdf/10.1007%2Fs11468-018-0727-1.pdf

Multi-Band Circular Dichroism Induced by Surface Plasmonic Resonance in Bi-Layer Semi-Ring / Rod Nanostructure

The dynamic refractive-index-change behavior of the light-induced process in an Mn:Fe:KTN crystal illuminated by a focused light sheet can be observed experimentally by digital holographic interferometry. By numerically retrieving a series of sequential phase maps from recording digital holograms, the spatial and temporal evolution of the light-induced refractive-index-change distribution inside the material is visualized in situ and monitored in a quantitative and in full field way. With this technique, the effect of recording parameters, such as writing laser power and polarization, bias voltage, temperature, and writing time, on the Mn:Fe:KTN crystal in the photorefractive effect can be explored. Therefore, optimized recording parameters will be achieved according to the dynamic behavior. The method provides an access to explore the evolution of the photorefractive (PR) effect of electrooptic crystal under various situations.

Visualization of Spatial–Temporal Evolution of Light-Induced Refractive Index in Mn:Fe:KTN Co-Doped Crystal Based on Digital Holographic Interferometry

Baozhen Ge

Papers

Field-induced lifetime enhancement of photorefractive gratings in a Mn:Fe:KTN crystal

Improving the performance of ultra-flexible perovskite photodetectors through cation engineering

Temperature dependence of Kerr coefficient and quadratic polarized optical coefficient of a paraelectric Mn:Fe:KTN crystal

Multi-Band Circular Dichroism Induced by Surface Plasmonic Resonance in Bi-Layer Semi-Ring / Rod Nanostructure

Visualization of Spatial–Temporal Evolution of Light-Induced Refractive Index in Mn:Fe:KTN Co-Doped Crystal Based on Digital Holographic Interferometry