Broadband all-fiber optical phase modulator based on photo-thermal effect in a gas-filled hollow-core fiber

We report broadband all-fiber optical phase modulation based on the photo-thermal effect in a gas-filled hollow-core fiber.The phase modulation dynamics are studied by multi-physics simulation.A phase modulator is fabricated using a 5.6-cm-long anti-resonant hollow-core fiber with pure acetylene filling.It has a half-wave optical power of 289 mW at 100 kHz and an average insertion loss 0.6 dB over a broad wavelength range from 1450 to 1650 nm.The rise and fall time constants are 3.5 and 3.7μs,respectively,2–3 orders of magnitude better than the previously reported microfiber-based photo-thermal phase modulators.The gas-filled hollow-core waveguide configuration is promising for optical phase modulation from ultraviolet to mid-infrared which is challenging to achieve with solid optical fibers.

Single‐precursor phase‐controlled synthesis of copper selenide nanocrystals and their conversion to amorphous hollow nanostructures

The crystal phases are essential to the physicochemical properties and functionalities of materials.Copper selenide has emerged as an important and appealing semiconductor,which can exist in a variety of polymorphic phases.However,the richness of polymorphs also makes it a challenge to the direct preparation of copper selenide nanocrystals with tunable phases.Herein,two polymorphs,that is,quasitetragonal Cu2−xSe nanocubes and metastable wurtzite Cu2Se nanodisks,are successfully synthesized by using a single precursor,copper(I)selenocyanate(CuSeCN),as the Cu and Se sources.The key to phase modulation is the optimal choice of the ligand in the synthesis.The as‐prepared nanocrystals possess different morphologies and compositions,giving rise to distinct optical properties and electrical conductivities.Interestingly,the copper selenide nanocrystals can provide a platform for the rational construction of two types of amorphous hollow Au─Cu─Se nanostructures by reaction with Au(I)precursor,in which their final shapes are well kept as that of the original nanocrystal templates.This work provides an easy strategy for the phase‐controlled synthesis of copper selenide nanocrystals and enables the design of new materials for broad applications.

Mid-infrared all-optical modulators based on an acetylene-filled hollow-core fiber

We report all-optical mid-infrared phase and intensity modulators based on the photo-thermal effect in an acetylene-filled anti-resonant hollow-core fiber.Optical absorption of the control beam promotes the gas molecules to a higher energy level,which induces localized heating through non-radiative relaxation and modulates the refractive index of the gas material and hence the accumulated phase of the signal beam propagating through the hollow-core fiber.By modulating the intensity of the control beam,the phase of the signal beam is modulated accordingly.By use of a 1.53μm near-infrared control beam,all-optical phase modulation up to 2.2πrad is experimentally demonstrated at the signal wavelength of 3.35μm.With the phase modulator placed in one arm of a Mach-Zehnder interferometer,intensity modulation with on-off ratio of 25 dB is achieved.The gas-filled hollow-core-fiber modulators could operate over an ultra-broad wavelength band from near-to mid-infrared and have promising application in mid-infrared photonic systems.

Surface coatings of two-dimensional metal-organic framework nanosheets enable stable zinc anodes

Aqueous zinc-ion batteries (ZIBs) have been considered as safe and scalable energy storage solutions,but the dendrite and corrosion issues of Zn anodes have hindered their further application.Herein,we demonstrate that two-dimensional metalorganic framework (MOF) nanosheets can act as protective coatings to prevent dendrite formation and hydrogen evolution of Zn anodes.The morphology of MOFs was tuned from octahedral nanoparticles (UiO-67-3D) to nanosheets (UiO-67-2D),leading to significantly enhanced protective performance.UiO-67-2D nanosheets-coated Zn anodes displayed smaller polarization,longer cycling lifetime and lower H_(2) evolution than those of UiO-67-3D nanoparticles in symmetrical cells,which has been attributed to the higher concentration of surface Zr-OH/H_(2)O to induce uniform Zn deposition and one-dimensional (1D) channels perpendicular to the Zn surface to regulate Zn^(2+) diffusion.The assembled UiO-67-2D@Zn||Mn_(2)O_(3)/C full cell shows a high capacity of240 m Ah g^(-1)at 1 A g^(-1) and excellent cycling stability.