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Polymer dielectrics with a high energy density, an outstanding breakdown strength, and a low dielectric loss are currently in great demand in the field of film capacitors. Here, on the basis of fundamental understanding of dielectric relaxation in cellulose, environmentally friendly regenerated cellulose-based dielectrics were fabricated by manipulating their intrinsic hydrogen bonding network, in which hydroxyl groups of cellulose were reacted with epichlorohydrin (ECH) to simultaneously reduce the density of the intra- and intermolecular hydrogen bonding networks and the crystallinity for activating the movement of polar groups. As a result, when the molar ratio of ECH to glucose units of cellulose is 1:1, the regenerated cellulose-based dielectrics exhibited the highest dielectric constant of 9.7 at 103 Hz with the dielectric loss in an order of 10−2 and an energy density of 2.16 J/cm3 with a high charge–discharge efficiency of >85% at 200 MV/m. This methodology presented here provides a promising avenue for designing and improving the dielectric properties of cellulose-based dielectrics.

Mode coupling between a square microcavity and a Fabry-Perot (FP) cavity is proposed and demonstrated for realizing single mode lasers. The modulations of the mode Q factor as simulation results are observed and single mode operation is obtained with a side mode suppression ratio of 46 dB and a single mode fiber coupling loss of 3.2 dB for an AlGaInAs/InP hybrid laser as a 300-μm-length and 1.5-μm-wide FP cavity connected to a vertex of a 10-μm-side square microcavity. Furthermore, tunable single mode operation is demonstrated with a continuous wavelength tuning range over 10 nm. The simple hybrid structure may shed light on practical applications of whispering-gallery mode microcavities in large-scale photonic integrated circuits and optical communication and interconnection.

The coherence of an electron beam is crucial for the performance of electron microscopy, coherent diffractive imaging, holography, and many other advanced instrumentation methods that rely on the phase coherence of electron waves. Here we present a reliable method for preparing a niobium nanoemitter, which is thermally and chemically stable. The tip apex is a (100) facet with a lateral dimension of ∼1 nm, surrounded by four (310) facets. Adsorption of one monolayer of noble gas, particularly Xe, onto the nanoemitter greatly enhances the emission current and current stability. This electron source will probably possess both spatial and temporal coherence if the emitter is cooled below the superconducting temperature.

A doping-free poly-Ge film as channel material was implemented by CVD-deposited nano-crystalline Ge and visible-light laser crystallization, which behaves as a p-type semiconductor, exhibiting holes concentration of 1.8 × 1018 cm−3 and high crystallinity (Raman FWHM ∼ 4.54 cm−1). The fabricated junctionless 7 nm-poly-Ge FinFET performs at an Ion/Ioff ratio over 105 and drain-induced barrier lowering of 168 mV/V. Moreover, the fast programming speed of 100 μs–1 ms and reliable retention can be obtained from the junctionless poly-Ge nonvolatile-memory. Such junctionless poly-Ge devices with low thermal budget are compatible with the conventional CMOS technology and are favorable for 3D sequential-layer integration and flexible electronics.

We experimentally study the characteristics of an integrated semiconductor twin-microdisk laser under mutually optical injection through a connected optical waveguide. Based on the lasing spectra, four-wave mixing, injection locking, and period-two oscillation states are observed due to the mutually optical injection by adjusting the injected currents applied to the two microdisks. The enhanced 3 dB bandwidth is realized for the microdisk laser at the injection locking state, and photonic microwave is obtained from the electrode of the microdisk laser under the period-two oscillation state. The plentifully dynamical states similar as semiconductor lasers subject to external optical injection are realized due to strong optical interaction between the two microdisks.

High-speed directly modulated microlasers are potential light sources for on-chip optical interconnection and photonic integrated circuits. In this Letter, dynamic characteristics are studied for microring lasers by rate equation analysis considering radial carrier hole burning and diffusion and experimentally. The coupled modes with a wide radial field pattern and the injection current focused in the edge area of microring resonator can greatly improve the high speed response curve due to the less carrier hole burning. The small-signal response curves of a microring laser connected with an output waveguide exhibit a larger 3 dB bandwidth and smaller roll-off at low frequency than that of the microdisk laser with the same radius of 15 μm, which accords with the simulation results.

Growth dynamics and unit cell migration of ferroelectric (Ba,Sr)TiO3 thin films were systematically studied with in situ reflective high-energy electron diffraction and atom force microscopy. By measuring the amplitudes of slow surface recovery oscillations of SrTiO3 film grown on (001) SrTiO3 surface, the activation energy of unit cell surface self-diffusion was surprisingly found to be only 0.29±0.01eV. A “unit-cell migration” model was developed to understand the epitaxial growth dynamics of ferroelectric thin films, which is a critical issue in oxide thin film growth and crucial in controlling the atomic structures.

Using large-area graphene sheets of 1-10 layers prepared by the improved liquid phase exfoliation technique, the mode locking operation of a diode-pumped Yb:KGW laser was demonstrated. Near-transform-limited 428 fs pulses were yielded at 1031.1 nm with an output power of 504 mW, corresponding to the slope efficiency of 27% and peak power of 13.8 kW. The output power ratio and the slope efficiency ratio of mode locking to free running were as high as 93% and 100%, respectively. This demonstration may open a proper way to achieve low-cost and efficient femtosecond bulk laser.

This work demonstrates the feasibility of a terahertz time-domain spectrometer based on a subwavelength-diameter plastic wire (SPW) for sensing applications. The dispersion property of the SPW is experimentally and theoretically studied. The SPW exhibits a low and controllable waveguide dispersion, which can be engineered by changing the core diameter, the core index, and the cladding index of the wire. Two white powders, tryptophan and polyethylene, deposited on the bottom of the wire can be successfully distinguished based on the waveguide dispersion of SPW. The SPW would be a promising candidate for combination with biochips for sensing minute molecules.

Perovskite heteroepitaxy was investigated under various conditions using laser molecular beam epitaxy. Well-controlled BaTiO3∕SrTiO3 heterostructure was studied with in situ reflective high energy electron diffraction and ex situ atomic force microscopy, x-ray diffraction, and transmission electron microscopy. The growth mode map of BaTiO3 thin films was obtained as a function of substrate temperature under 600°C for various laser repetition rates. The effective activation energy of surface migration was determined to be 0.33eV. A mechanism of surface migration in BaTiO3 heteroepitaxy was described for a basic understanding of atomic-scale controlled preparation of ferroelectric heterostructures at low temperature.

Oxygen diffusion at the SrTiO3∕Si interface was analyzed. A method called temperature gradient modulation growth was introduced to control oxygen diffusion at the interface of SrTiO3∕Si. Nanoscale multilayers were grown at different temperatures at the initial growing stage of films. Continuous growth of SrTiO3 films was followed to deposit on the grown sacrificial layers. The interface and crystallinity of SrTiO3∕Si were investigated by in situ reflection high energy electron diffraction and x-ray diffraction measurements. It has been shown that the modulated multilayers may help suppress the interfacial diffusion, and therefore improve SrTiO3 thin film properties.

By using ultraviolet photoelectron spectroscopy, the hole-injection barrier of poly-(9,9-dioctylfluorene) (PFO) cast on top of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) electrode is found to vary with thickness of both films, as confirmed by current profiles of hole-dominated and bipolar devices. The variation can be attributed to a migration of PSS chain as a dopant into PFO layer, as indicated by the broadening and shifting (towards higher binding energy) of highest occupied molecular orbital edge peak of PFO film. The barrier at the thinnest PEDOT:PSS film (15nm) is found to be the smallest due to the least extent of doping by PSS chains.