Electrically driven supersymmetric semiconductor laser arrays with single-lobe far-field patterns.

Semiconductor laser arrays based on the third-order supersymmetric (SUSY) transformation are proposed to increase the mode discrimination between fundamental supermode and high-order supermodes. The distance between the edge waveguide of the main array and that of the superpartners is optimized. Then, the electric field distributions of different modes are also calculated, which show that, except for the fundamental supermode, the high-order supermodes penetrate deeper into the superpartner arrays, which accounts for the increased loss of high-order supermodes. The fabricated third-order SUSY laser array can emit light with a single-lobe far-field pattern under an injection current of 70 mA, which is a promising candidate for optical couplings between lasers and optical elements.

Different phases in non-Hermitian topological semiconductor stripe laser arrays.

As a novel branch of topology, non-Hermitian topological systems have been extensively studied in theory and experiments recently. Topological parity-time (PT)-symmetric semiconductor stripe laser arrays based on the Su-Schreiffer-Heeger model are proposed. The degree of non-Hermicity can be tuned by altering the length of the cavities, and PT symmetry can be realized by patterned electrode. Three laser arrays working in different non-Hermitian phases are analyzed and fabricated. With the increasing degree of non-Hermicity, the peaks of output intensities move from the edge to the bulk. The proposed semiconductor stripe laser array can function as an active, flexible, and feasible platform to investigate and explore non-Hermitian topology for further developments in this field.

Electrically injected supersymmetric semiconductor lasers with narrow vertical divergence angle.

Electrically injected supersymmetric (SUSY) semiconductor lasers are proposed and fabricated. Two successive SUSY transformations are applied to the main array arranged along the direction of epitaxial growth, which can remove the propagation constants of the fundamental mode and the leaky mode of the main array from the superpartner while keeping those of other high-order modes. The SUSY laser possesses an excellent mode discrimination and favors the lasing of the fundamental mode. The fabricated SUSY laser can emit light with a single-lobe vertical far-field pattern with the full width at half maximum of 16.87° under an injection current of 1.4 A.

Approaches to tuning the exceptional point of PT-symmetric double ridge stripe lasers.

Electrically injected Parity-time (PT)-symmetric double ridge stripe semiconductor lasers lasing at 980 nm range are designed and measured. The spontaneous PT-symmetric breaking point or exceptional point (EP) of the laser is tuned below or above the lasing threshold by means of varying the coupling constant or the mirror loss. The linewidth of the optical spectrum of the PT-symmetric laser is narrowed, compared with that of traditional single ridge (SR) laser and double ridge (DR) laser. Furthermore, the far field pattern of the PT-symmetric laser with EP below the lasing threshold is compared with that of the PT-symmetric laser with EP above the lasing threshold experimentally. It is found that when the laser start to lase, the former is single-lobed while the latter is double-lobed. when the current continues to increase, the former develops into double lobe directly while the latter first develops into single lobe and then double lobe again.

Ultrasensitive and Wearable Carbon Hybrid Fiber Devices as Robust Intelligent Sensors.

The growing applications of wearable electronics, electronic textiles, and biomedical devices have sparked explosive demand for high-performance flexible sensors. Herein, we report a facile approach for fabricating a highly sensitive carbon hybrid fiber, which is composed of a graphene fiber skeleton and carbon nanotube (CNT) branches. In this hierarchical fiber, in situ grown CNTs prohibit the stacking of graphene sheets and bridge graphene layers simultaneously, making the hybrid fiber fluffy and conductive. Due to the well-designed architecture, the assembled fiber sensor exhibits satisfactory performance with a high gauge factor (up to 1127), a fast response time (less than 70 ms), and excellent reliability and stability (>2000 cycles). This work provides a feasible and scalable pathway for the fabrication of ultrasensitive fiber-based sensors, achieving the full realization of monitoring human physiological signals and architecting a real-time human-machine controlling system. Moreover, these practical sensors are used to monitor the sitting posture to prevent cervical spondylosis and lumbar disc herniation.

Ultrafast Microwave Polarizing Electrons to Form Vertically Aligned Metal Hybrids as Lithiophilic Buffer for Lithium-Metal Batteries.

Lithium-metal batteries (LMBs) have attracted great attention because of their high theoretical capacity and low electrochemical potential. However, uncontrollable Li dendrite growth and significant volume expansion result in safety issues that largely limit their practical applications. Herein, we explore a microwave-assisted strategy for the rapid synthesis of vertically aligned metal hybrids on Cu foil (VAMH@CF). Such an elaborate architecture of VAMH provides a lithiophilic buffer layer after prelithiation, offering vast nucleation sites/seeds for Li deposition (Li@VAMH@CF) and lower nucleation overpotential. Consequently, Li@VAMH@CF exhibits an outstanding cyclability with a long lifespan (up to 5500 cycles) and a low voltage hysteresis (28 mV) in a symmetrical cell at 3 mA cm-2. LiFePO4||Li@VAMH@CF full cells deliver a reversible capacity of about 140 mAh g-1 for 200 cycles, further demonstrating opportunities of the microwave-involved strategy for optimizing Li-metal anodes.

Selective Solid-Liquid Interface Sulfidation Growth of Hierarchical Copper Sulfide and Its Hybrid Nanoflakes for Superior Lithium-Ion Storage.

Two-dimensional metal sulfides and their hybrids are emerging as promising candidates in various areas. Yet, it remains challenging to synthesize high-quality 2D metal sulfides and their hybrids, especially iso-component hybrids, in a simple and controllable way. In this work, a low-temperature selective solid-liquid sulfidation growth method has been developed for the synthesis of CuS nanoflakes and their hybrids. CuS nanoflakes of about 20 nm thickness and co-component hybrids CuOx /CuS with variable composition ratios derived from different sulfidation time are obtained after the residual sulfur removal. Besides, benefiting from the mild low-temperature sulfidation conditions, selective sulfidation is realized between Cu and Fe to yield iso-component FeOx /CuS 2D nanoflakes of about 10-20 nm thickness, whose composition ratio is readily tunable by controlling the precursor. The as-synthesized FeOx /CuS nanoflakes demonstrate superior lithium storage performance (i. e., 707 mAh g-1 at 500 mA g-1 and 627 mAh g-1 at 1000 mA g-1 after 450 cycles) when tested as anode materials in LIBs owing to the advantages of the ultrathin 2D nanostructure as well as the lithiation volumetric strain self-reconstruction effect of the co-existing two phases during charging/discharging processes.

Synthesis and Properties of two CuI Complexes Involving Tetrathia-fulvalene-Fused Phenanthroline Ligand.

Two CuI complexes based on the π-conjugated tetrathiafulvalene-annulated phenanthroline ligands (TTF-Phen, L1 and L2), [CuI(Xantphos)(L1)]BF4 (1, Xantphos = 9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene) and [CuI(Binap)(L2)]BF4 (2, Binap = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl), have been synthesized. They have been fully characterized, and their photophysical and electrochemical properties are reported together with those of L1 and L2 for comparison. Both CuI complexes show metal-to-ligand charge transfer (MLCT) absorption bands, whereas the 3MLCT luminescence is strongly quenched.