Ba0.6 Sr0.4 TiO3-ZnNb2O6复相微波介质陶瓷的结构与介电性能研究

以Ba0.6Sr0.4TiO3为基体材料,采用传统陶瓷制备工艺,制备了Ba0.6 Sr0.4 TiO3-ZnNb2O6(简称BSTZ)复相微波介质陶瓷.结果表明,BSTZ复相陶瓷可在1200℃烧结成瓷,烧结温度明显低于Ba0.6Sr0.4TiO3陶瓷的烧结温度,并反应生成新相BaNb3.6O10.在室温低频下,随ZnNb2O6含量的增加,BSTZ复相陶瓷的介电常数下降;在1.6kV/mm的直流偏压下,各BSTZ复相陶瓷的可调性随ZnNb2O6添加量增加而减小.     

High dielectric tunability with high thermal stability of the (111) highly oriented 0.85Pb(Mg1/3Nb2/3)-0.15PbTiO3 thin film prepared by a sol-gel method

Ferroelectric thin films with high tunability, low dielectric loss, high figure-of-merit (FOM) and high thermal stability are attractive to military and civil tunable devices such as phase shifters, filters, etc. In this work, the (100), (110) and (111) highly oriented 0.85Pb(Mg_1/3Nb_2/3)-0.15PbTiO₃ (PMN-15PT) relaxor ferroelectric thin films were prepared by a sol-gel method. The (111) highly oriented PMN-15PT thin film has high dielectric tunability (η) value of ∼ 80% at 1500 kV/cm, high thermal stability (±2% variation) from room temperature to ∼ 450 K and the dielectric tunability is independent from 500 Hz to 10 kHz. The high dielectric tunability of the (111) highly oriented PMN-15PT thin film is associated to the reorientation of polar nanoregions (PNRs) and intrinsic lattice phonon polarization. Meanwhile, the excellent thermal stability may be attributed to the large dielectric diffuseness degree (γ ∼ 1.81) derived from the modified Curie-Weiss law. It is believed that the (111) highly oriented PMN-15PT thin film is an attractive material in the application of the next-generation tunable devices.     

Tunable optical filters with wide wavelength range based on porous multilayers

A novel concept for micromechanical tunable optical filter (TOF) with porous-silicon-based photonic crystals which provide wavelength tuning of ca. ±20% around a working wavelength at frequencies up to kilohertz is presented. The combination of fast mechanical tilting and pore-filling of the porous silicon multilayer structure increases the tunable range to more than 200 nm or provides fine adjustment of working wavelength of the TOF. Experimental and optical simulation data for the visible and near-infrared wavelength range supporting the approach are shown. TOF are used in spectroscopic applications, e.g., for process analysis.     

含稀土配合物的聚丙烯酸酯的荧光可调控性能研究

用化学络合的方法制得含弱荧光稀土离子镨Pr(Ⅲ)和铒Er(Ⅲ)的单体,并经自由基聚合方法制得含Pr(Ⅲ)和Er(Ⅲ)的聚丙烯酸酯聚合物.通过对聚合物薄膜的荧光分析发现,敏化离子La(Ⅲ)、Y(Ⅲ)、Yb(Ⅲ)的引入,使含弱荧光稀土离子镨Pr(Ⅲ)和铒Er(Ⅲ)的聚丙烯酸酯表现出了明显的荧光发射特性,且通过引入这些敏化离子,可实现对上述聚合物的特征荧光发射光谱的调控作用;同时发现敏化离子Yb(Ⅲ)对上述两种聚合物的荧光调控作用都较为明显.     

丝网印刷B-Li玻璃掺杂Ba0.5Sr0.5TiO3厚膜介电性能研究

钛酸锶钡(BST)陶瓷材料在外置偏压直流电场作用下,具有高的介电可调性,可以广泛地应用于电可调陶瓷电容器以及无源可调微波器件的设计与开发.通过B-Li玻璃的有效掺杂,实现BST陶瓷材料与Ag、Cu贱金属电极材料的低温友好烧结,是发展混合集成厚膜电路的技术要求.主要采用丝网印刷工艺,在Al2O3陶瓷衬底上,制备了B-Li玻璃掺杂的Ba0.5Sr0.5TiO3厚膜材料,并对其最佳烧结温度、物相结构、显微形貌以及介电性能进行了研究.结果表明,B-Li玻璃掺杂的Ba0.5Sr0.5TiO3厚膜材料在950℃可以实现低温烧结,得到了厚度为20μm的均匀致密厚膜材料;相比于BST陶瓷块体材料,5%(质量分数)B-Li玻璃掺杂BST厚膜的居里峰发生了明显的弥散和宽化,介电常数显著降低;在室温和10kHz频率下,其介电常数为210,介电损耗为0.0037,介电可调性可达15%以上,可以适用于厚膜混合集成电路与可调器件的设计和开发.     

全固化可调谐Yb:YAG激光器

实现了半导体激光器抽运的全固化Yb:YAG激光器的可调谐运转,当吸收抽运功率为900mW时,在中心波长1049.5nm处得到66mW的连续激光输出.采用1%的输出耦合镜时单侧抽运阈值为410mW,双侧抽运阈值为380mW,斜率效率为12.7%.对该激光器的可调谐特性进行了详细的研究,得到1030.5～1055.5nm范围内的连续可调谐.同时得到自调Q脉冲序列.     

A novel structure of DFB laser for the generation of 40 GHz self-pulsation

1.55·μm InGaAsP-InP two-section DFB lasers with varied ridge width, both gain-coupled and index-coupled, have been fabricated. Self-pulsations with frequencies around 40 GHz are observed. The related mechanism and the tunability of generated self-pulsations is studied.     

溅射气压对Bi1.5Mg1.0Nb1.5O7薄膜结构及介电性能的影响

采用射频磁控溅射法在Pt/Si基片上沉积了铌酸铋镁(Bi1.5Mg1.0Nb1.5O7,BMN)薄膜.研究了溅射气压对BMN薄膜结构、表面形貌、化学成分及介电性能的影响.结果表明,制备的薄膜具有立方焦绿石结构.高溅射气压下制备的BMN薄膜晶粒的平均尺寸比低溅射气压下制备的薄膜晶粒的大.薄膜的介电调谐率及相对介电常数随溅...     

Harnessing Surface Wrinkle Patterns in Soft Matter

Mechanical instabilities in soft materials, specifically wrinkling, have led to the formation of unique surface patterns for a wide range of applications that are related to surface topography and its dynamic tuning. In this progress report, two distinct approaches for wrinkle formation, including mechanical stretching/releasing of oxide/PDMS bilayers and swelling of hydrogel films confined on a rigid substrate with a depth‐wise modulus gradient, are discussed. The wrinkling mechanisms and transitions between different wrinkle patterns are studied. Strategies to control the wrinkle pattern order and characteristic wavelength are suggested, and some efforts in harnessing topographic tunability in elastomeric PDMS bilayer wrinkled films for various applications, including tunable adhesion, wetting, microfluidics, and microlens arrays, are highlighted. The report concludes with perspectives on the future directions in manipulation of pattern formation for complex structures, and potential new technological applications.     

Reprogrammable Phononic Metasurfaces

Phononic metamaterials rely on the presence of resonances in a structured medium to control the propagation of elastic waves. Their response depends on the geometry of their fundamental building blocks. A major challenge in metamaterials design is the realization of basic building blocks that can be tuned dynamically. Here, a metamaterial plate is realized that can be dynamically tuned by harnessing geometric and magnetic nonlinearities in the individual unit cells. The proposed tuning mechanism allows a stiffness variability of the individual unit cells and can control the amplitude of transmitted excitation through the plate over three orders of magnitude. The concepts can be extended to metamaterials at different scales, and they can be applied in a broad range of engineering applications, from seismic shielding at low frequency to ultrasonic cloaking at higher frequency ranges.