一种胶体光子晶体修饰的光纤

设计了一种胶体光子晶体修饰的光纤. 采用恒温快速蒸发法直接在经切割刀处理后的光纤端面生长胶体晶体,再与另一根切割后的光纤在毛细玻璃管中完成对接,制备成胶体光子晶体修饰的光纤. 用扫描电子显微镜和光谱分析仪对样品的形貌、结构以及光学特性进行分析. 实验结果表明,粒径为640 nm、体积分数约为0.5%的SiO₂胶体微球溶液在60 ℃的情况下沉积,大约12 h后可得到质量较高的胶体光子晶体. 在SEM下,观察到端面的胶体晶体为面心立方(fcc)结构. 透射光谱证明,该结构在(111)面上     

中心外缺陷对带隙型光子晶体光纤色散特性的影响

利用时域有限差分法(FDTD)模拟仿真了在中心缺陷外出现点缺陷、空气柱位错和内层空气柱发生形变三种缺陷形态对光子带隙型光子晶体光纤(PBG-PCF)色散特性的影响.发现一方面缺陷的出现会使色散曲线趋于平坦,另一方面点缺陷和位错缺陷的出现会使零色散点向长波移动,内层空气柱的形变使零色散点向短波长移动.这对PBG-PCF的实际生产实践会有指导意义.     

光学微盘腔与三能级量子点系统中的模耦合研究

用一种全量子理论方法研究了波导、光学微盘腔与三能级量子点耦合系统的动力学过程,求出其耦合后的透射模和反射模的解析解. 由于微腔表面粗糙引起反向散射,在微腔内形成两简并回音壁耦合共振模,其耦合率为β;量子点的两激发态分别以耦合率g₁,g₂与回音壁耦合共振模产生耦合. 在实数空间里,得出透射光谱和反射光谱的数值解,这些三能级模型结果比二能级模型结果更接近真实光学微盘腔系统,能更好地显示耦合系统的动力学特性.     

双包层多芯光子晶体光纤自相干合成的数值分析与实验

依据耦合模理论分析了双包层多芯光子晶体光纤的超模模场特性,通过倏逝波对7束光的相位调节,可实现相干合成,激光亮度得到很大提高.利用相干合成原理对双包层多芯光子晶体光纤的出射光相干功率密度进行了分析与测量,对此种结构的光子晶体光纤实现自相干合成提出了理论和实验依据.     

掺Eu~(2+)的卤磷酸盐的发光特性和内部能量传递

探讨Ｂａ２＋离子搀杂对（Ｃａ０．５Ｓｒ０．５）５（ＰＯ４）３Ｃｌ：Ｅｕ２＋和（Ｃａ０．４Ｓｒ０．６）５（ＰＯ４）３Ｃｌ：Ｅｕ２＋量子发光效率的影响。当用Ｂａ２＋离子代替Ｃａ２＋或Ｓｒ２＋离子进入晶体时，Ｅｕ２＋离子的发光特性发生改变：发射峰的峰值降低，热猝灭的温度升高。并采用位型坐标理论给予解释。根据晶体的结构特征，对占据两个不等当晶体学位置的Ｅｕ２＋离子发光中心之间的能量传递进行了探讨     

双量子阱结构OLED效率和电流的磁效应

通过结构为ITO/NPB(60 nm)/ Alq₃ ∶1 wt% rubrene(20 nm)/ Alq₃(3 nm)/ Alq₃ ∶1 wt% rubrene(20 nm)/ Alq₃(20 nm)/LiF/Al的双量子阱的黄色有机电致发光器件,研究了不同磁场强度下的发光效率和电流变化特性. 研究结果表明该器件的电流是随着磁场强度的增加而单调下降的,显示了器件的电阻是随着磁场强度的增加而增加的. 同时也得到了该结构有     

水下量子通信的数值模拟及误码率分析

水下量子密钥分配可以为水下通信提供绝对安全的保密手段。本文采用蒙特卡洛方法,结合海水信道的光学性质和光子的量子特性模拟了光子在海水中的传输过程,研究其衰减和偏振特性,计算了接收到的光子数随接收端口径、视场角和传输距离的变化,从保真度的角度分析散射光的偏振变化情况,并结合背景光的影响分析了水下量子通信误码率。结果表明,水下量子通信理论上可以实现百米量级的安全通信。     

各向异性光子晶体中二能级原子和自发辐射场间的纠缠

应用 Von Neumann熵 和 Schmidt number K两种纠缠度量讨论了各向异性光子晶体中二能级原子和自发辐射场间纠缠度的演化性质. 研究发现,原子-光场纠缠度的演化与原子上能级和光子晶体能带带边的相对位置有关,当原子上能级处于光子晶体禁带内,原子-光场纠缠度将保持稳定,当原子上能级处于光子晶体能带中,原子-光场纠缠度先增大后衰减到零. 纠缠度的大小还与原子的初态有关. 可以通过控制原子的初态和原子上能级与带边的相对位置来控制原子-光场纠缠度的演化特性.     

光子晶体光纤带隙及模场的一种综合模拟分析方法

提出直接由MATLAB读入光纤端面图实现复杂结构光子晶体光纤(PCF)模型的快速建立,并综合平面波法(PWM)和频域有限差分(FDFD)法,模拟分析带隙型光子晶体光纤(PBG-PCF)的带隙和模场分布.利用PWM计算得到了在PBG-PCF中传输的光波频率及模式有效折射率范围;基于FDFD法在给定波长及模式有效折射率范围情况下,模拟得到了PBG-PCF中可能存在的模场分布及其他特性.以市售的PBG-PCF为例,验证了数值模拟的正确性,随后系统地分析了结构参数(晶格结构、"原子"占有率、背景材料折射率及"原子     

一种红光增强型白光LED特性研究

通过对YAG:Ce3+荧光粉掺杂方案的改进,引入Pr3+离子,改善了荧光粉发光特性,使白光LED发光光谱在610 nm处出现发射峰,红光成分增强。通过1 400 h左右老化实验,荧光粉发射峰的2个主峰强度变化表明:当Pr3+浓度增大到一定程度,荧光粉稳定性下降;色度变化表明:2种配比荧光粉的LED色偏移量均0.015,具有很好的色度稳定性。     

Determination of stratospheric aerosol parameters from two-wavelength lidar sensing data

We calculate the microphysical characteristics of stratospheric aerosol from lidar-sensing data at wavelengths of 355 and 532 nm using a priori information about the aerosol spectra obtained from balloon and aircraft measurement data. We analyze the mode structure of the spectra and its coupling with the integral microphysical characteristics of aerosol. For most implementations, it was shown that two aerosol modes (of background and volcanic natures) make commensurate contributions to integral aerosol characteristics, which makes it difficult to use the traditional method of model estimates. It is more efficient to use an optical model of a statistical character that is based on approximation dependences between the required integral aerosol characteristics and lidar-measured optical characteristics. We found that the area, volume, and effective size of particles and the lidar ratio at a wavelength of 355 nm correlated with the absolute values of backscattering coefficients at wavelengths of 355 or 532 nm and the lidar ratio at the wavelength of 532 nm correlated with the ratio of backscattering coefficients at these wavelengths. We estimate the error in the determination of integral characteristics of aerosol using the model developed. The model efficiency is demonstrated on real data of stratospheric aerosol lidar sensing.     

基于闪锌矿晶体中受激电磁耦子散射产生可调谐太赫兹波的理论研究

基于受激电磁耦子散射原理,采用已报道的利用非线性光学参量振荡方法产生可调谐太赫兹波的实验条件作为理论分析的实验模型,以GaAs,GaP, InP,ZnTe晶体为代表,计算分析了在闪锌矿晶体中参量振荡产生太赫兹波的吸收、增益特性,对输出THz波的调谐特性给出了详尽分析.分析太赫兹波高效耦合输出的腔型结构,并与掺氧化镁铌酸锂晶体组成的太赫兹波参量振荡器做对比.     

The structure of the nearshore branch of the Tsushima current on the shelf off the San'in coast in summer

Current measurements were made at five moored stations over the continental shelf off the San'in coast of the Japan Sea for a month in the summer of 1980 to study the vertical structure of the nearshore branch of the Tsushima Current. The time-mean current for the observational period is 20 to 25 cm sec^–1 eastward near the surface and about 10 cm sec^–1 westward near the sea bottom except at the shallowest station. The time-mean current,i.e. the nearshore branch of the Tsushima Current is mainly due to the baroclinic modes. The currents are less variable in the first half of the observational period, but fluctuate with a several-day period in the latter half. The obtained current data were decomposed into barotropic and baroclinic modes to investigate the detailed characteristics of the fluctuations. In the latter half, the current fluctuations of the two modes with about a 5-day period are well correlated with each other, as the baroclinic mode lagging behind the barotropic mode by 12 hr. The barotropic current fluctuation is correlated to the sea level, with the former leading the latter by about 12 hr. The baroclinic current is correlated to the temperature at the subsurface layer with a shorter time lag.     

Modification of the spontaneous emission of quantum dots near the surface of a three-dimensional colloidal photonic crystal

This paper demonstrates experimentally and numerically that a significant modification of spontaneous emission rate can be achieved near the surface of a three-dimensional photonic crystal. In experiments, semiconductor core-shell quantum dots are intentionally confined in a thin polymer film on which a three-dimensional colloidal photonic crystal is fabricated. The spontaneous emission rate of quantum dots is characterised by conventional and time-resolved photoluminescence (PL) measurements. The modification of the spontaneous emission rate, which is reflected in the change of spectral shape and PL lifetime, is clearly observed. While an obvious increase in the PL lifetime is found at most wavelengths in the band gap, a significant reduction in the PL lifetime by one order of magnitude is observed at the short-wavelength band edge. Numerical simulation reveals a periodic modulation of spontaneous emission rate with decreasing modulation strength when an emitter is moved away from the surface of the photonic crystal. It is supported by the fact that the modification of spontaneous emission rate is not pronounced for quantum dots distributed in a thick polymer film where both enhancement and suppression are present simultaneously. This finding provides a simple and effective way for improving the performance of light emitting devices.     

Estimation of the necessary contrast of optical interference filters for ozone measurements in the atmosphere

The requirements imposed on the spectral characteristics of optical filters for portable optical ozonometers are analyzed; when satisfied, they make it possible to determine the total atmospheric ozone to an accuracy no lower than the accuracy achieved by complex spectral slit instruments. Considered is the dependence of the calculated ozone absorption coefficients on the spectral characteristic of the filters and total ozone for the nonmonochromatic radiation measured with two optical filters. Estimates of the role of contrast and permissible values of the background transmittance of filters in the range of 294.8–400 nm are presented. With these estimates taken into account, it is recommended in two-filter ozonometers to use interference filters with a transmission maxima at 305.5–307 and 326–330 nm with a spectral width of their bands at half of the height of the maximum transmission of 2–5 nm.     

低维半导体异质结中的量子相干红外发射机理理论研究

给出了一种在非粒子反转条件下量子阱和量子点激光器的红外发射机理. 此种红外发射是基于在同一作用区产生并作为红外场相干源的两种带间跃迁激光场的共振非线性混合. 这种频率下转换机理并不依赖于在半导体激活媒质中的长时相干假定条件,在室温和泵注入电流条件下仍然有效. 频率下转换的固有效率可以达到相当于每个可见光子产生一个红外光子的量子极限值. 根据红外发射的可参变特性,这种非粒子反转的方法尤其适用于长波红外工作范围.     

Validation of ADEOS-II GLI ocean color products using in-situ observations

The Global Imager (GLI) aboard the Advanced Earth Observing Satellite-II (ADEOS-II) made global observations from 2 April 2003 to 24 October 2003. In cooperation with several institutes and scientists, we obtained quality controlled match-ups between GLI products and in-situ data, 116 for chlorophyll-a concentration (CHLA), 249 for normalized water-leaving radiance (nLw) at 443 nm, and 201 for aerosol optical thickness at 865 nm (Tau_865) and Angstrom exponent between 520 and 865 nm (Angstrom). We evaluated the GLI ocean color products and investigated the causes of errors using the match-ups. The median absolute percentage differences (MedPD) between GLI and in-situ data were 14.1–35.7% for nLws at 380–565 nm, 52.5–74.8% nLws at 625–680 nm, 47.6% for Tau_865, 46.2% for Angstrom, and 46.6% for CHLA, values that are comparable to the ocean-color products of other sensors. We found that some errors in GLI products are correlated with observational conditions; nLw values were underestimated when nLw at 680 nm was high, CHLA was underestimated in absorptive aerosol conditions, and Tau_865 was overestimated in sunglint regions. The error correlations indicate that we need to improve the retrievals of the optical properties of absorptive aerosols and seawater and sea surface reflection for further applications, including coastal monitoring and the combined use of products from multiple sensors.     

油藻混合水体遥感反射比光谱分析

辐射传输模式HydroLight是研究水体辐射传输特性的有效工具,同时也是进行石油类水体辐射传输特性的有效模型。本文基于2018年8月在辽宁大连港海域实测的石油类污染水体的表观及固有光学量数据,通过设置不同浓度的配比模拟试验,利用HydroLight对油类物质和藻类物质的单一组分和两者混合水体的遥感反射比（remote sensing reflectance,R_rs）光谱进行了模拟。模拟结果表明：（1）在仅含油类物质单一组分的水体中,R_rs随着油浓度C_oil的变化分为两个特征波段：400~480 nm和480~700 nm。在400~480 nm波段范围内R_rs随C_oil的增加而减小,在480~700 nm随C_oil的增大而增大;（2）在仅含藻类物质的单一成分水体中,叶绿素的光谱特性需要其浓度C_chl达到一定值才能表现出来,在低C_chl时的R_rs光谱特性反映为纯水的光谱特性;（3）在油藻混合水体中,随C_oil的增加会增大叶绿素的R_rs,但不会明显改变叶绿素的R_rs随波长的变化趋势,这说明油藻混合水体的光谱形状主要受叶绿素的影响,油类物质的存在只改变光谱的量值。利用HydroLight对石油类污染水体的R_rs展开研究,有助于丰富水色遥感基础研究,对完善各类水体生物光学模型研究具有重要的理论意义。