The Effect of Lateral Guiding Mechanism on Noise Characteristics in Semiconductor Lasers

A comparison between intensity noise spectra and also the line shapes of gain-guided, weakly-index-guided, and strongly-index-guided semiconductor lasers are made using numerical solution of Maxwell-Bloch equations including spontaneous emission noise.

A New Thread Guide Mechanism of Rubbed Roving Frame

A new thread guide mechanism of a rubbed roving frame is developed, which consists mainly of a plate cam, a linkage and an air bag spring. Characteristics and design parameters of the air spring are explored in this study. Based on analyses of winding technology for this kind of package, the kinetic laws of the thread guide is put forward. General design equations of the cam profile are derived, and common kinetic laws of II linkage group which is used for such mechanism design is proposed. It proves theoretically that it is practicable. The experimental results indicate that it can meet the needs of technological demands, and the new thread guide mechanism has been used successfully on textile machines.

Quasiperiodic photonic crystal fiber[Invited]

In the fields of light manipulation and localization,quasiperiodic photonic crystals,or photonic quasicrystals[PQs],are causing an upsurge in research because of their rotational symmetry and long-range orientation of transverse lattice arrays,as they lack translational symmetry.It allows for the optimization of well-established light propagation properties and has introduced new guiding features.Therefore,as a class,quasiperiodic photonic crystal fibers,or photonic quasicrystal fibers[PQFs],are considered to add flexibility and richness to the optical properties of fibers and are expected to offer significant potential applications to optical fiber fields.In this review,the fundamental concept,working mechanisms,and invention history of PQFs are explained.Recent progress in optical property improvement and its novel applications in fields such as dispersion control,polarization-maintenance,supercontinuum generation,orbital angular momentum transmission,plasmon-based sensors and filters,and high nonlinearity and topological mode transmission,are then reviewed in detail.Bandgap-type air-guiding PQFs supporting low attenuation propagation and regulation of photonic density states of quasiperiodic cladding and in which light guidance is achieved by coherent Bragg scattering are also summarized.Finally,current challenges encountered in the guiding mechanisms and practical preparation techniques,as well as the prospects and research trends of PQFs,are also presented.

Reprogrammable 3D Mesostructures Through Compressive Buckling of Thin Films with Prestrained Shape Memory Polymer

The mechanically guided assembly that relies on the compressive buckling of strate- gically patterned 2D thin films represents a robust route to complex 3D mesostructures in advanced materials and even functional micro-devices. Based on this approach, formation of complex 3D configurations with suspended curvy features or hierarchical geometries remains a challenge. In this paper, we incorporate the prestrained shape memory polymer in the 2D precur- sor design to enable local rolling deformations after the mechanical assembly through compressive buckling. A theoretical model captures quantitatively the effect of key design parameters on local rolling deformations. The combination of precisely controlled global buckling and local rolling expands substantially the range of accessible 3D configurations. The combined experimental and theoretical studies over a dozen of examples demonstrate the utility of the proposed strategy in achieving complex reprogrammable 3D mesostructures.

Morphable three-dimensional electronic mesofliers capable of on-demand unfolding

Development of miniaturized three-dimensional(3 D)fliers with integrated functional components has important implications to a diverse range of engineering areas.Among the various active and passive miniaturized 3 D fliers reported previously,a class of 3 D electronic fliers inspired by wind-dispersed seeds show promising potentials,owing to the lightweight and noiseless features,aside from the stable rotational fall associated with a low falling velocity.While on-demand shape-morphing capabilities are essential for those 3 D electronic fliers,the realization of such miniaturized systems remains very challenging,due to the lack of fast-response 3 D actuators that can be seamlessly integrated with 3 D electronic fliers.Here we develop a type of morphable3 D mesofliers with shape memory polymer(SMP)-based electrothermal actuators,capable of large degree of actuation deformations,with a fast response(e.g.,~1 s).Integration of functional components,including sensors,controllers,and chip batteries,enables development of intelligent 3 D mesoflier systems that can achieve the on-demand unfolding,triggered by the processing of real-time sensed information(e.g.,acceleration and humidity data).Such intelligent electronic mesofliers are capable of both the low-air-drag rising and the low-velocity falling,and thereby,can be used to measure the humidity fields in a wide 3 D space by simple hand throwing,according to our demonstrations.The developed electronic mesofliers can also be integrated with other types of physical/chemical sensors for uses in different application scenarios.