Fano profile in a novel double cavity optomechanical system with harmonically bound mirrors

We investigate a double cavity optomechanical system generating single and double Fano resonance (multi-Fano). By altering a single parameter, the tunnelling rate g of the middle mirror, we are able to switch between single and double Fano line shapes. The first spectral line shape is stronger in the case of multi-Fano than in the case of single Fano. Also the behaviour of the steady state value of the displacement of the middle mirror, with respect to g, heavily influences the behaviour of double Fano lines in our scheme. This tunability along with using a single pump and signal/probe laser has an added advantage in situations where only low power consumption is available.     

Analysis,design and simulation of MIM plasmonic filters with different geometries for technical parameters improvement

In this paper, four optical filter topologies based on metal–insulator–metal waveguides are proposed and the designed structures are investigated numerically using finite-difference timedomain method. Triangular-shaped adjunctions have been added to the filter structures to improve their transmission spectrum. These improved structures consist of air as the insulator and silver as the metal. The relative permittivity of metal has been described via the Drude,Drude–Lorentz, and Palik models. The first filter's transmission spectrum shows an acceptable transmittance. In the second optimized filter, the transmission spectrum has been improved. The transmittance spectrum can be tuned through adjusting the edge of the triangle in these four optimized filters. As a result, the bandwidths of resonance spectra can be adjusted. The theory of such tapered structures will be investigated by the tapered transmission line and will be solved with the transfer matrix method. This method shows a better performance and higher transmission efficiency in comparison with the basic structures. On the other hand, the final filter has been chosen as the best one because of its hexagonal resonator. The main reason for having a better result is due to a longer interaction length in comparison with the circular resonator. This in turn creates much better energy coupling and results in higher transmission.     

无机钙钛矿太阳能电池Cs2SnI6的电子结构和光学性质的第一性原理研究

近年来,Cs2SnI6作为一种无毒性、稳定性好的新型钙钛矿材料应用于太阳能电池中,其电池的光电转换效率由最初不到1%增长到现在的8.5%,使之成为有可能替代铅基钙钛矿太阳能电池的新型太阳能电池。本文采用基于广义密度泛函和杂化密度泛函的第一性原理方法研究了Cs2SnI6的电子结构、光学特性和钙钛矿太阳能电池的光电性能参数。研究结果表明,导带底和价带顶位于同一高对称点Γ而属于直接跃迁型半导体,且电子态主要来自于I-5p轨道和Sn-5s轨道。在近红外和可见光波长范围内有较高的吸收系数,当Cs2SnI6钙钛矿厚度达到10μm时,吸收率在311~989 nm之间接近100%,不考虑潜在损失的情况下,理论上太阳能电池可获得短路电流为32.86 mA/cm2、开路电压0.91 V、填充因子87.4%、光电转换效率26.1%。为实验上制备高效Cs2SnI6钙钛矿太阳能电池提供了参考。     

Dielectrophoretically Modulated Optical Spectroscopy of Colloidal Nanoparticle Solutions in Microfluidic Channels

Optical spectroscopic techniques (e.g., extinction, scattering, and fluorescence spectroscopies) are important for the analysis of colloidal solutions of nanoparticles (NPs). They are routinely applied to plasmonic and quantum-dot NP samples assuming that these contain a single population of particles with modest size and shape dispersity. However, these spectroscopic techniques become less effective when the sample is a mixture of particles with different sizes, shapes, or composition. Here, an original microfluidic method is proposed for the optical spectroscopic analysis of colloidal NP solutions that combines periodic trapping of NPs by dielectrophoresis (DEP) with in situ optical extinction spectroscopy. The periodic trapping leads to modulation of the continuously monitored optical spectrum depending on the DEP properties of the NPs. DEP-modulated spectroscopy is demonstrated using colloidal gold NPs as small as 40 nm diameter. It is found that the DEP modulation is significantly enhanced when employing suitable microfluidic flow over a multielectrode array. Finally, it is shown that the method can identify and characterize the NP species simultaneously present in a mixture of 40 and 80 nm gold NPs, opening the way toward optical spectroscopic analysis of higher complexity NP mixtures through the combination of the DEP-modulated spectroscopy with chemometric methods.     

高分辨率微型星载相机光学系统的设计及应用

为了克服太空环境的复杂性,满足航天工程的空间使用要求,研制一款2 500万像素宽光谱共焦成像的微型星载相机光学系统。该系统适应卫星发射和在轨道运行的恶劣环境,具有抗冲击震动、耐太空高温差强辐射,体积小,质量轻等优点。设计的系统可在450 nm～800 nm的谱段内清晰成像,焦距181 mm,入瞳口径45 mm,视场角10.4°,边缘相对照度0.81,轴上点MTF:0.57@55 lp/mm,0.33@110 lp/mm,畸变1.2%,镜头质量622 g,外形尺寸Φ58.3 mm×117 mm,抗辐照性能≥5 krad。通过温度适应性的模拟和优化,用户进行?30 ℃～+70 ℃光学镜头热真空试验,可正常工作。该系统已成功应用于天宫二号伴飞卫星相机中,获得的图像清晰稳定,为空间遥感实验观测发挥了重要的作用。     

大视场反射式施密特光学系统设计与检测

大视场、低成本、高性能天文望远镜是当前研究和开发的热点。基于像差平衡原理,在正入射施密特矫正板基础上推导出斜入射反射式施密特矫正板方程,针对焦距1 700 mm,成像视场角4°,波段为0.4 μm～0.9 μm,F数为4.25的光学系统,求解出施密特矫正板方程,并作为初始结构参数代入Zemax软件进一步优化。设计结果表明,在全视场范围内,该系统在奈奎斯特频率100 lp/mm处的调制传递函数MTF大于0.35,畸变小于2.5%,成像质量达到了衍射极限。优化设计后施密特矫正板与最近球面最大偏差为0.005 mm,采用特制的补偿器结合干涉仪可完成面形高精度检测。该施密特系统的设计为大视场、宽波段天文望远镜的开发提供了参考。     

FFT动态相位重建算法的滤波窗影响分析

为了优化相位重建算法,针对波面干涉图的傅里叶频谱,分析了不同滤波窗口的分布特征和频谱响应,通过计算机仿真和实验测试,确定了FFT动态相位重建算法的最佳滤波窗口类型。其中处理仿真干涉图重建的波面与原始波面的波面峰谷值残差为0.008 5λ,波面均方根值残差为0.000 1λ;处理实验干涉图获得的波面与移相干涉测量法获得的波面峰谷值残差为0.009 3λ,波面均方根值残差为0.000 5λ。结果表明:选取Hamming窗进行滤波处理并重建的相位经拟合后得到的波面较参考波面的面形残差最小,相位重建精度优于0.01λ,可进一步应用于大口径光学元件的测量中。     

手机虹膜识别镜头设计

随着近年来图像传感器的快速商用化以及生物识别算法的发展,虹膜识别功能得以应用于移动终端设备。获取虹膜图像是虹膜识别的关键一步,运用ZEMAX光学设计软件设计了一款适用于手机的虹膜识别镜头。该镜头采用豪威科技公司OmniVision_OV2281传感器,采用三片式非球面光学塑料设计,F数为2.3,全视场角为34°,在1/2奈奎斯特频率220 lp/mm处MTF值均大于0.39,且系统总长仅3 mm。根据ZEMAX像质评价方法以及公差分析结果可知,该镜头各项光学指标优良,具有像质好、体积小,质量轻、价格低、容易加工等特点。     

暗怪波的相互作用

以耦合非线性薛定谔方程为理论模型,数值研究了两个一阶暗怪波在正常色散单模光纤中的相互作用.基于一阶暗怪波精确解,采用分步傅里叶数值模拟法,从间距、相位差和振幅系数比方面讨论相邻两个一阶暗怪波之间的相互作用.基于二阶暗怪波精确解,讨论了两个一阶暗怪波的非线性相互作用.研究结果表明:同相位情况下,间距参数T1为0、5、20时,相邻两个一阶暗怪波相互作用激发产生“扭结型”暗怪波.相比较于单个暗怪波发生能量的弥散,“扭结型”暗怪波分裂形成多个次暗怪波.反相位情况下,间距参数T1为2、7、12时,相邻两个一阶暗怪波相互作用也可以激发产生“扭结型”暗怪波.并且“扭结型”暗怪波初始激发的空间位置偏离原始单个暗怪波的位置5.振幅系数比越大,该空间位置越接近5.二阶暗怪波可以看作是两个一阶暗怪波的非线性叠加,复合型和三组分型二阶暗怪波与相邻两个一阶暗怪波的相互作用略有相似.     

基于EKF的水下LD通信精对准控制算法

高速激光通信中接收机与光斑中心很难处于精对准状态,导致水下光通信链路难以稳定建立.首先采用蒙特卡洛仿真统计法分析激光光子在海水中传输的接收光强分布规律,再通过实验对接收端的光斑图像进行采样分析,利用曲线拟合得到接收器位置与接收光强的关系.仿真与实验结果表明:光束经过25 m的水下传输,接收光强分布仍近似为高斯分布.采用非线性估计算法(扩展卡尔曼滤波)与基本状态控制反馈理论,根据接收光强度估计接收器当前位置与最大光强处的距离,通过反馈算法实现接收端与光斑中心的主动跟踪对准.算法仿真结果显示,接收端对准误差在2 mm以下,稳定后接收效率超过98%.