磁过滤多弧离子镀C/C多层膜在模拟体液中的微磨粒磨损行为

采用磁过滤直流阴极真空弧源沉积技术在Ti6Al4V表面制备C/C多层DLC膜,利用纳米压痕划痕仪测试薄膜的纳米硬度和膜-基结合强度,采用微磨粒磨损试验机对C/C多层DLC膜在模拟体液环境中的磨损性能进行评价,并与Ti6Al4V的耐磨性能进行对比.结果表明:C/C多层DLC膜硬度达54.82 GPa,弹性模量和划痕临界载荷分别为342.27 GPa和0.52 N;在模拟体液环境中DLC膜的耐磨性能显著优于Ti6Al4V合金,DLC膜的磨损机制主要包括二体磨损及混合磨损;随着料浆浓度的增加,DLC膜的磨损机制从二体磨损向混合磨损过渡.     

平面天线在场效应晶体管太赫兹探测器中的应用

为了提高场效应晶体管太赫兹探测器的响应度并降低噪声等效功率,需要对探测器集成平面天线的结构进行合理设计与优化,本文对集成平面天线结构的场效应晶体管太赫兹探测器的研究进行了深入调研。首先,对场效应晶体管太赫兹探测器的工作原理进行了分析,介绍了集成平面天线如何解决耦合太赫兹波效率低的问题。然后,介绍了一些常用的平面天线结构,包括偶极子天线、贴片天线、缝隙天线、grating-gate和其他类型的结构,比较了各种天线的性能以及引入后对太赫兹探测器响应度的影响。通过对比不同天线结构的探测器响应度和噪声等效功率等参数指标,发现:采用平面天线结构之后,场效应晶体管太赫兹探测器的响应度有了大幅度的提升,各种类型的天线对探测器响应度都有不同程度的提升。本文着重介绍了几种集成于场效应晶体管的平面天线结构,包括各种天线的性能和研究进展,最后分析了场效应晶体管太赫兹探测器存在的问题和发展趋势。     

Surface plasmon-enhanced dual-band infrared absorber for VO_x-based microbolometer application

We propose a periodic structure as an extra absorption layer(i.e., absorber) based on surface plasmon resonance effects, enhancing dual-band absorption in both middle wavelength infrared(MWIR) and long wavelength infrared(LWIR)regions. Periodic gold disks are selectively patterned onto the top layer of suspended SiN/VO_2/SiN sandwich-structure.We employ the finite element method to model this structure in COMSOL Multiphysics including a proposed method of modulating the absorption peak. Simulation results show that the absorber has two absorption peaks at wavelengths λ =4.8 μm and λ = 9 μm with the absorption magnitudes more than 0.98 and 0.94 in MWIR and LWIR regions, respectively. In addition, the absorber achieves broad spectrum absorption in LWIR region, in the meanwhile, tunable dual-band absorption peaks can be achieved by variable heights of cavity as well as diameters and periodicity of disk. Thus, this designed absorber can be a good candidate for enhancing the performance of dual band uncooled infrared detector, furthermore, the manufacturing process of cavity can be easily simplified so that the reliability of such devices can be improved.     

Analysis of resonance asymmetry phenomenon in resonator integrated optic gyro

Resonator integrated optic gyro(RIOG) is a high-accuracy gyroscope based on the Sagnac effect. The waveguidetype ring resonator is a key rotation sensing element in the RIOG. An asymmetric resonance line shape is found in the optic resonator. These asymmetries will induce offset errors when the phase modulation spectroscopy technique(PMST)is applied to the RIOG. The polarization errors and the difference among normal mode losses are found to be the two main sources of resonance asymmetry in an experiment. These sources are fully investigated and their contributions to the offset errors are compared. The analysis shows that proper modulation frequencies in clockwise(CW) and counterclockwise(CCW) directions can reduce an RIOG bias error. A transmissive resonator is recommended to obtain a better resonance line shape.     

Optical absorption enhancement in slanted silicon nanocone hole arrays for solar photovoltaics

We investigate slanted silicon nanocone hole arrays as light absorbing structures for solar photovoltaics via simulation.With only 1-μm equivalent thickness, a maximum short-circuit current density of 34.9 m A/cm~2 is obtained. Moreover, by adding an Ag mirror under the whole structure, a short-circuit current density of 37.9 m A/cm~2 is attained. It is understood that the optical absorption enhancement mainly results from three aspects. First, the silicon nanocone holes provide a highly efficient antireflection effect. Second, after breaking the geometric symmetry, the slanted silicon nanocone hole supports more resonant absorption modes than vertical structures. Third, the Fabry–Perot resonance enhances the light absorption after adding an Ag mirror.