[en] In this paper, the properties of the combined temperature field of zirconia, alumina and metal have been studied by using the simulation software CGSim. For the first time, a thermal insulation system with the combination of molybdenum, zirconia and alumina screen has been proposed. By keeping the side of the screen thickness unchanged, the heat preservation effect of temperature field turns out to be worse when the molybdenum screen with the same thickness is replaced with alumina. To ensure internal molybdenum screen layers unchanged, the insulation effect of temperature field is significantly enhanced with increasing the thickness of alumina or zirconia, the power consumption is decreased. However, the decrease of power consumption slows down when the thickness of alumina or zirconia increase to a certain thickness. (paper)

[en] A diode-end-pumped acousto-optical Q-switched composite YVO₄/Nd:YVO₄/YVO₄ crystal self-Raman laser at the second-Stokes wavelength of 1314 nm is demonstrated. The maximum average output power at 1314 nm was obtained to be 1.4 W with the corresponding optical conversion efficiency of 4.1%. The shortest pulse width, the maximum pulse energy and the highest peak power were measured to be 1.1 ns, 40 μJ and 28.7 kW, respectively. (letter)

[en] Two-dimensional layered materials have been widely utilized as nonlinear absorption materials to transfer continue-wave into pulse trains in fiber laser systems. Here, we prepare robust GaSe/GeSe composites with high power bearing capacity as saturable absorbers (SAs) and then investigate their nonlinear optical properties via broadband Z-scan measurement at 800 nm and 1550 nm, respectively. The modulation depths of GaSe/GeSe based SAs are measured to be 11.97% and 7.69% at 1550 nm. After incorporating the GaSe/GeSe SAs into an Erbium-doped fiber laser cavity, passively Q-switched pulse trains could be obtained with repetition rates changing from 83.58 to 136.78 kHz (70.41 to 161.65 kHz). The maximum output power and pulse energy are 52.1 mW/370.67 nJ (GaSe) and 21.6 mW/133.74 nJ (GeSe) under the maximum pump power of 600 mW. The results indicate that GaSe and GeSe possess outstanding thermal stability and could be employed as remarkable saturable absorption materials for high-energy pulses generation. (paper)

[en] We propose and numerically investigate a kind of high-efficiency T-shaped optical circulator in a two-dimensional square-lattice photonic crystal. In the T-shaped structure, the single-direction light transmission for 90° light-bending is achieved by coupling two magneto-optical rods. And aided with a side-coupled cavity, two paths of single-direction 90° light-bending are effectively combined, which realizes the nonreciprocal light transmission for two waveguides arranged and linked along a straight line. The optical properties of the system are investigated by finite element method. The circulator considered here can be used for isolating light reflections and improving system stabilization in designing photonic crystal integrated circuits. -- Highlights: ► We design a T-shaped three-port circulator in a magneto-photonic crystal. ► A single-direction 90° light-bending is realized by coupling two magneto-optical rods. ► Two paths of 90° light-bending are effectively combined by a side-coupled cavity. ► The designed circulator has compact structure and high efficiency. ► The circulator can be used to build photonic crystal integrated optical circuits.

[en] We report on the generation of large pulse duration-tuning and wide wavelength-tunable mode-locked pulses, operating in a dissipative soliton resonance (DSR) region, by an all-normal-dispersion Yb-doped figure-eight fibre laser. For the case of a DSR operating at 1045.1 nm, the pulse duration varies from 26.3 ps to 8.621 ns with the increase of pump power. At the maximum pump power of 400 mW, the pulse energy is as high as 4.8 nJ. In particular, through properly adjusting the polarization controllers, the DSR can be wavelength-tuned in a wide range from 1037.3 to 1075.3 nm. To the best of our knowledge, this is the widest tunable range ever reported for DSR operation. This wavelength-tunable mode-locked fibre laser with a high-energy output may be well-suited for many potential applications. (letter)

[en] Bismuth-based binary compounds, including Bi₂Se₃ and Bi₂Te₃, have attracted increasing attention as well-known topological insulators. On the other hand, bismuth-based ternary compounds exhibit diverse properties, such as, ultrahigh carrier mobility, and strong Rashba spin splitting. Moreover, they boast of superior photocatalytic properties, implying great potential to be used in a wide range of applications. The unique structure and properties of two-dimensional (2D) materials, especially the extraordinary electronic and optical properties of 2D Bi₂O₂Se, have given rise to significant research interests for the exploration of 2D bismuth-based ternary compounds. In this review, we will comprehensively discuss the properties of three important families of bismuth-based ternary compounds, including Bi₂O₂X (X = S, Se, Te), BiTeX (X = Cl, Br, I), and BiOX (X = Cl, Br, I). In particular, we have placed emphasis on the latest progress in their 2D forms, including their novel properties and applications. This review would aid in understanding the superior performance of bismuth-based ternary compounds and offer a perspective for future research on these emerging 2D materials. (topical review)

[en] We predict the existence of a surface plasmon polariton (SPP) mode that can be guided by a graphene monolayer, regardless of the sign of the imaginary part of its conductivity. In this mode, in-plane electron oscillations along two surfaces of graphene are of opposite directions, which is very different from conventional SPPs on graphene. Significantly, coating graphene with dielectric films yields a way to guide the SPPs with both sub-wavelength mode widths and ultra-long propagation distances. In particular, the mode characteristics are very sensitive to the chemical potential of graphene, so the graphene-based waveguide can find applications in many optoelectronic devices

[en] This study aims to examine the influence law of polyhedron structure on the spatial mechanical properties of ultra-high-speed rotating mirrors. To this end, polyhedral beryllium alloy rotating mirrors are investigated on the basis of elastoplastic theory and finite element method. The maximum stress is located at the end position of the contact between the shaft and the mirror body. Stress increases with the number of mirror faces. The different structures have a negative stress gradient. The structural strength of rotating mirror is affected by the strength of the mirror body material in high-speed rotation of the tensile force of centrifugal force. The lateral deformation of the mirror surface is caused by the combined effect of compression of centrifugal force generated by the material of sharp-corner and the tretching of tensile force caused by the material at the centre of the mirror at high-speed rotation. The amount of mirror surface deformation is not proportional to the number of faces. The rotating mirror with iso-quadrangular structure has the best lateral deformation effect. This research provides a theoretical basis for the research and design of rotating mirrors with high potential value. (paper)

[en] The present paper introduces micro ultrasonic powder molding (micro-UPM), a novel method for forming micro semi-crystalline polymer parts. In the proposed method, semi-crystalline polymer powder is rapidly heated and plasticized by ultrasonic vibration, after which the microcavity is filled with the melt under sonotrode pressure (P_U) to form a variety of micro polymer parts. Differential scanning calorimetry, scanning electron microscopy, and nanoindentation tests demonstrate that micro-UPM UHMWPE (ultra-high molecular weight polyethylene) parts consists of nascent and melt-recrystallized phases and that energy concentrated at particle interfaces as a result of high-frequency friction, compressive deformation, and ultrasonic radiation leads to rapid diffusion and interpenetration of the chain segment. The particle interface melts result in strong co-crystallization during cooling. To investigate the effect of ultrasonic duration time (T_U) on the quality of micro-UPM UHMWPE parts, different T_U values are utilized to form UHMWPE parts at a P_U of 16 MPa and a holding time of 5.0 s. As T_U increases, the number and sizes of interparticle voids gradually decrease. A rise in the melting peak of the melt-recrystallized phase and a drop in the melting peak of the nascent phrase as well as crystallinity are further observed. When T_U is only 1.5 s, the crystallinity of the micro plastic part reaches a minimum value of 54.3% and the melt-recrystallized phase fraction reaches a maximum value of 98.3%. Powder particle interfaces almost disappear in this case, and optimum quality of the micro-UPM UHMWPE part is achieved. (paper)

[en] Excimer laser emitting at 248 nm is applied to produce microstructures on the surface of aluminum alloy. The surface morphology shows that hotspots and thermal fluidic structures both come to light. Two possible mechanisms of hotspots formation are proposed: near-field diffraction and interference, and extremely fast rapid thermal annealing. And for the formation of thermal fluidic pattern structure, a thin film model is applied.