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<jats:title>Abstract</jats:title> <jats:p>Monolayer transition metal dichalcogenides (TMDs) are widely used for integrated optical and photoelectric devices. Owing to their broken inversion symmetry, monolayer TMDs have a large second-order optical nonlinearity. However, the optical second-order nonlinear conversion efficiency of monolayer TMDs is still limited by the interaction length. In this work, we theoretically study the second harmonic generation (SHG) from monolayer tungsten sulfide (WS<jats:sub>2</jats:sub>) enhanced by a silica microsphere cavity. By tuning the position, size, and crystal orientation of the material, second-order nonlinear coupling can occur between the fundamental pump mode and different second harmonic cavity modes, and we obtain an optimal SHG conversion efficiency with orders of magnitude enhancement. Our work demonstrates that the microsphere cavity can significantly enhance SHG from monolayer 2D materials under flexible conditions.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Magnetoresistance (MR) provides rich information about Fermi surface, carrier scatterings, and exotic phases for a given electronic system. Here, we report a study of the magnetoresistance for the metallic states in twisted double bilayer graphene (TDBG). We observed quadratic magnetoresistance in both moiré valence band (VB) and moiré conduction band (CB). The scaling analysis shows validity of Kohler’s rule in the moiré valence band. On the other hand, the quadratic magnetoresistance appears near the halo structure in the moiré conduction band, and it violates Kohler’s rule, demonstrating the MR scaling related to band structure in TDBG. We also proposed an alternative scaling near the halo structure. Further analysis implies the observed quadratic magnetoresistance and alternative scaling in conduction band are related to the halo boundary. Our results may inspire investigation on MR in twisted 2D materials and provide new knowledge for MR study in condensed matter physics.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We theoretically investigate the yield enhancement of elliptical high harmonics in the interaction of molecules with bicircular laser pulses by solving the time-dependent Schrödinger equation. It is shown that, through adjusting the relative intensity ratio of the two bicircular field components in specific ranges, the yield of the molecular high harmonics for the plateau and cutoff regions can be respectively enhanced. To analyze this enhancement phenomenon, we calculate the weights of the electron classical trajectories. Additionally, we also study the ellipticity distribution of harmonics for different intensity ratios. It is found that these enhanced harmonics are elliptically polarized, which is mainly attributed to the recombination dipole moment of the major weighted trajectories. These enhanced elliptical extreme ultraviolet and soft x-ray radiations may serve as essential tools for exploring the ultrafast dynamics in magnetic materials and chiral media.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this paper, we investigate certain rogue waves of a (3 + 1)-dimensional BKP equation via the Kadomtsev-Petviashili hierarchy reduction method. We obtain semirational solutions in the determinant form, which contain two special interactions:(1) one lump develops from a kink soliton and then fuses into the other kink one; (2) a line rogue wave arises from the segment between two kink solitons and then disappears quickly. We find that such a lump or line rogue wave only survives in a short time and localizes in both space and time, which performs like a rogue wave. Furthermore, the higher-order semi-rational solutions describing the interaction between two lumps (one line rogue wave) and three kink solitons are presented.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A flower-like SnO<jats:sub>2</jats:sub>-SnO/porous GaN (FSS/PGaN) heterojunction was fabricated for the first time via a facile spraying process, the whole process also involved hydrothermal preparation of FSS and electrochemical wet etching of GaN, and SnO<jats:sub>2</jats:sub>-SnO composites with p-n junctions were loaded onto PGaN surface directly applied to H<jats:sub>2</jats:sub>S sensor. Meanwhile, the excellent transport capability of heterojunction between FSS and PGaN facilitates electron transfer, that is, a response time as short as 65 s and a release time up to 27 s can be achieved merely at 150 ℃ nder 50 ppm H<jats:sub>2</jats:sub>S concentration, which has laid a reasonable theoretical and experimental foundation for the subsequent PGaN-based heterojunction gas sensor. The lowering working temperature and high sensitivity (23.5 at 200 ppm H<jats:sub>2</jats:sub>S) are attributed to the structure of PGaN itself and the heterojunction between SnO<jats:sub>2</jats:sub>-SnO and PGaN. In addition, the as-obtained sensor showed ultra-high test stability. The simple design strategy of FSS/PGaN-based H<jats:sub>2</jats:sub>S sensor highlights its potential in various applications.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The high efficiency and low production cost enable the halide perovskite solar cells as a promising technology for the next generation photovoltaics. Nevertheless, the relatively poor stability of the organic-inorganic halide perovskites hinders their commercial applications. In the past few years, two-dimensional (2D) perovskite has emerged as a more stable alternative to the three-dimensional (3D) counterparts and attracted intense research interests. Although many attempts and advances have been made, it is still ambiguous that whether the 2D perovskites could bring closure to the stability issue. To answer this essential question, a systematic study of the nature of 2D halide perovskites is necessary. Here, we focus on the stability investigations of 2D perovskites from different perspectives, especially light, heat, ion migration and strain. Several remaining challenges and opening problems are also discussed. With further material and device engineering, we believe that the 2D perovskites would promote perovskite solar cells to a promising future.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The multiplexing technology based on the superconducting quantum interference device (SQUID) is crucial to the cryogenic readout of superconducting transition-edge sensor (TES) arrays. The demands for large-scale TES arrays promote the development of multiplexing technologies towards large multiplexing factors and low readout noise. The development of multiplexing technologies also facilitates new applications of TES arrays in a wide range of frequencies. Here this paper summarizes different types of SQUID-based multiplexing technologies including time-division multiplexing, code-division multiplexing, frequency-division multiplexing and microwave SQUID multiplexing. The advances and parameter constraints of each multiplexing technology are also discussed.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>There exists an optimal range of intensity of chaotic force in which the behaviors of chaos‐driven bistable system with two weak inputs can be consistently mapped to specific logic output. The phenomenon is called logical chaotic resonance (LCR). However, realization of reliable exclusive disjunction (XOR) through LCR has not been reported. Here, we explore the possibility of using chaos to enhance the reliability of XOR logic operation in a triple‐well potential system via LCR. The success probability <jats:italic>P</jats:italic> of obtaining XOR logic operation can take maximum value 1 in an optimal window of intensity <jats:italic>D</jats:italic> of chaotic force. Namely, success probability <jats:italic>P</jats:italic> displays characteristic bell‐shaped behavior by altering intensity of chaos driving force, indicating the occurrence of LCR phenomenon. Further, the effects of periodic force on LCR have been investigated. For subthreshold chaotic force, periodic force with appropriate amplitude and frequency can help to enhance the reliability of XOR logic operation. Thus, LCR can be effectively regulated by changing amplitude and frequency of periodic force.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Broad area semiconductor lasers (BAL) have poor lateral beam quality due to lateral mode competition, which limits its application as a high-power optical source. The paper presents the study and results of distributed Bragg reflector laser diode with tapered grating (TDBR-LD). By introducing variation in lateral width, the tapered grating increases the loss of high-order lateral modes, thus improving the lateral characteristics of the laser diode. The measuring results show that the TDBR-LD can achieve single-lobe output under 0.9A. In contrast to straight distributed Bragg reflector laser diode (SDBR-LD), the lateral far field divergence of TDBR-LD was measured to be 5.23° at 1A, representing a 17% decline. The linewidth of TDBR-LD is 0.4nm at 0.2A, which is reduced by nearly 43% compared with that of SDBR-LD. Meanwhile, both of the devices have a maximum output power of approximate 470mW.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Models based on a parabolic equation (PE) can accurately predict sound propagation problems in range-dependent ocean waveguides. Consequently, this method has developed rapidly in recent years. Compared with normal mode theory, PE focuses on numerical calculation, which is difficult to use in the mode domain analysis of sound propagation, such as the calculation of mode phase velocity and group velocity. To broaden the capability of PE models in analyzing the underwater sound field, a wave mode calculation method based on PE is proposed in this study. Step-split Padé PE recursive matrix equations are combined to obtain a propagation matrix. Then, the eigenvalue decomposition technique is applied to the matrix to extract sound mode eigenvalues and eigenfunctions. Numerical experiments on some typical waveguides are per-formed to test the accuracy and flexibility of the new method. Discussions on different orders of Padé approximant demonstrate angle limitations in PE and the missing root problem is also discussed to prove the advantage of the new method. The PE mode method can be expanded in the future to solve smooth wave modes in ocean waveguides, including fluctuating boundaries and sound speed profiles.</jats:p>