Inspired by the quantum spin Hall effect shown topological insulators, we propose a plate structure that can be used to demonstrate pseudospin for flexural waves. The system consists of thin with periodically arranged resonators mounted on its top surface. We extend technique based plane-wave expansion method identify double Dirac cone emerging due zone-folding in frequency band structures. This particular design allows us move lower than resonating local resonators. then manipulate pattern...

Although there have been intense efforts to fabricate large three-dimensional photonic crystals in order realize their full potential, the technologies developed so far are still beset with various material processing and cost issues. Conventional top-down fabrications costly time-consuming, whereas natural self-assembly bottom-up often result high defect density limited dimensions. Here we report fabrication of extraordinarily monocrystalline by controlling processes which occur unique...

Smart glass offers dynamic control over the transmission of light to address various needs in energy conservation, privacy, and information display; yet, most existing technologies still require continuous power for operation are limited single functions (usually either tint or haze control). In this work, we have developed a versatile tristable smart based on cholesteric liquid crystal (CLC). The is voltage-switchable among three field-free stable states different optical properties, each...

Soft-matter-based photonic crystals like blue-phase liquid (BPLC) have potential applications in wide-ranging and bio-chemical systems. To date, however, there are limitations the fabrication of large monocrystalline BPLCs. Traditional crystal-growth process involves transition from a high-temperature disordered phase to an ordered (blue) is generally slow (takes hours) with limited achievable lattice structures, efforts improve molecular alignment through post-crystallization field...

Random lasing actions have been observed in optically isotropic pure blue-phase and polymer-stabilized liquid crystals containing laser dyes. Scattering, interferences recurrent multiple scatterings arising from disordered platelet texture as well index mismatch between polymer mesogen these materials provide the optical feedbacks for action. In stabilized crystals, coherent random could occur ordered blue phase with an extended temperature interval state. The dependence of wavelength range,...

Highly tunable 3D liquid photonic crystals are demonstrated using low-dc-field-driven polymer-stabilized blue-phase crystals. The central wavelength of the band gap can be reversibly shifted to more than 200 nm away from original position. Besides, by controlling polymerization-induced morphology variations, also expanded a bandwidth around 30 at least 310 nm, first time "white" blue phase is observed. Both types band-gap modulation, namely, shifting and expansion, independently manipulated...

The key challenge for high-power delivery through optical fibers is overcoming nonlinear effects. To keep a smooth output beam, most techniques mitigating nonlinearities are restricted to single-mode fibers. Moving out of the paradigm, we show experimentally that wavefront-shaping coherent input light highly multimode fiber can increase power threshold stimulated Brillouin scattering (SBS) by an order magnitude, whilst simultaneously controlling beam profile. SBS suppression results from...

The discovery of topologically non-trivial electronic systems has opened a new age in condensed matter research. From topological insulators to superconductors and Weyl semimetals, it is now understood that some the most remarkable robust phases (e.g., Quantum Hall or Anomalous Hall) are result protection. These powerful ideas have recently begun be explored also bosonic systems. Topologically protected acoustic, mechanical, optical edge states been demonstrated number recreate requisite...

High-power fiber laser amplifiers have enabled an increasing range of applications in industry, science, and defense. The power scaling for is currently limited by transverse mode instability. Most techniques suppressing the instability are based on single- or few-mode fibers order to output a clean collimated beam. Here, we study theoretically using highly multimode amplifier with many-mode excitation efficient suppression thermo-optical nonlinearity We find that mismatch characteristic...

Transverse Mode Instability (TMI) that results from dynamic nonlinear thermo-optical scattering is the primary limitation to power scaling in high-power fiber lasers and amplifiers. It has been proposed TMI can be suppressed by exciting multiple modes a highly multimode fiber. We derive semi-analytic frequency-domain theory of threshold for onset narrowband amplifiers under arbitrary input excitation general geometries. Our detailed model includes effect gain saturation, pump depletion,...

We demonstrate a normally transparent smart window based on cholesteric liquid crystal with negative dielectric anisotropy. The is electrically switchable between clear and diffuse states. state exhibits well-aligned planar texture stable in the absence of an electric field, while switched when applying field higher than undulation instability threshold. degree translucency can be controlled by varying strength. When applied removed, relaxes back to spontaneously. It also found that much...

The recent emergence of topological insulators in condensed matter physics has inspired analogous wave phenomena mechanical systems. However, to date, the design these systems been limited mostly discrete lattices or perforated structures. Here, we take a ubiquitous bolted elastic plate and demonstrate that it can guide flexural waves crisply around sharp bends. We show this continuum system eliminates unwanted in-plane modes allows manipulation low-frequency by exploiting local resonance...

This paper reports in situ formation of Au/Pt bimetallic nanoparticles on the surface polystyrene microspheres. was accomplished by dispersion copolymerization styrene and a poly(N-isopropylacrylamide) (PNIPAAm) macromonomer ethanol−water media presence HAuCl4 H2PtCl6. The particle size morphology microspheres can be changed varying molar ratio Au/Pt. propagation oligomer radicals nucleation were controlled ratio. A monodisperse microsphere, with as core PNIPAAm corona, obtained at 2/8....

This work proposes two mechanisms for switching the direction of stripes in cholesteric liquid crystal (CLC) gratings. The stripe depends on ratio cell gap to natural pitch length (d/P0) a CLC sample. Electrical is based different pitches at planar and transient states. Optical switching, however, changes by using photo-isomerization effect azobenzene doped Using mechanisms, we can switch directions orthogonal directions. Furthermore, beam-steering capability gratings also remains effective after

An electrically activated bistable light shutter that exploits polymer-stabilized cholesteric liquid crystal film was developed. Under double-sided three-terminal electrode driving, the device can be and switched between focal conic homeotropic textures with a uniform in-plane vertical electrical field. The transparent state transmittance of 80% opaque/scattering 13% realized without any optical compensation film, each simply to other by applying pulse voltage. Also, gray-scale selection...

Photorefractive effects manifested in two beam coupling and side diffractions are observed fullerene-C60 doped blue-phase liquid crystals (BPLC-C60) upon application of a DC bias field. The mechanism at work here is attributed to BPLC lattice distortion by the combined (Edc)+ photorefractive space-charge (Ephoto) fields, addition + optical field induced reported previous studies dye-doped system. first order diffraction efficiency ∼2×10-3 gain over 2% 55 μm thick sample with input laser...

We have experimentally demonstrated the feasibility of direct compression, or stretching and recompression laser pulses in a very wide temporal time scale spanning 10's fs to ~1 ps with sub-mm thick cholesteric liquid crystal (CLC) cells. The mechanisms at work here are strong dispersion photonic band-edges nonlinear phase modulation associated non-resonant ultrafast molecular electronic optical nonlinearity. observed pulse compression limit, spectral characteristics intensity dependence...

Liquid crystal random fiber lasers (LC-RFLs) exhibit low spatial coherence, extraordinary tunability, and high flexibility are therefore promising for use in imaging related applications. They nevertheless suffer from ineffective emission along the axis. This work develops an end-emitting LC-RFL that is based on a pump-induced gain–loss structure, which effectively modulates optical feedback, thereby providing directional lasing fiber. The laser comprises ∼10 000 transverse modes mutually...