以蓝色发光材料DPVBi为基质的白色发光器件

白色有机发光器件是实现彩色平板显示的重要方案之一。利用蓝色发光材料DPVBi[4，4′—(2，2—苯乙烯基)—1，1′—联苯]掺杂红光染料DCJTB[4—氰甲烯基—2—叔丁基—6—(1，1，7，7—四甲基久洛尼定基—9—烯炔基—4H—吡喃)]作发光层制备了白色发光器件。研究了DPVBi掺杂不同浓度IDCJTB薄膜的光致发光性质，根据光致发光结果，制备了以DPVBi掺杂不同浓度DCJTB作发光层的电致发光器件，其结构为ITO／GuPc／NPB／DPVBi：DCJTB／Alq3／LiF／Al。当DCJTB质量分数为0．0008时，器件实现了白色发光(色度x=0．25，y=0．32)，电致发光和光致发光的掺杂比例基本相符，表明器件的白色发光主要是由基质DPVBi向掺杂剂DCJTB的能量传递产生的。研究还发现：白色器件随电压升高，光谱中蓝色成分相对于红色成分的比例略有增加，文章对此现象进行了分析。该白光器件在14V时达到最高亮度7822cd／cm^2，在20mA／cm^2电流密度下的亮度为-489cd／cm^2，最大流明效率为1．75lm／W。     

蓝色发光材料DPVBi掺杂DCJTB发光性质的研究

对蓝光材料DPVBi掺杂红光染料DCJTB的发光性质进行了研究。首先研究了DPVBi掺杂不同质量浓度DCJTB的光致发光，当掺杂质量浓度为0.1％时，光致发光得到白光(色度x=0．36，y=0．34)。基于光致发光的实验结果，以DPVBi掺杂不同质量浓度DCJTB作发光层，制备了结构为ITO／CuPc／NPB／DPVBi：DCJTB/Alq3／LiF／Al的器件，当掺杂质量浓度为0．08％时器件实现了白色发光(色度为x=0．25，y=0．32)。研究了该白光器件的电致发光性质，白光器件在14V时达到最高亮度7822cd／m^2。在20mA／cm^2电流密度驱动下的亮度为489cd/m^2，最大流明效率为1．75lm／W。     

发光层厚度对联苯乙烯衍生物蓝色有机发光器件性能的影响

本文制备了联苯乙烯衍生物(4, 4'-bis(2, 2'-diphenylvinyl)-1, 1'-biphenyl, DPVBi) 为发光层的蓝色有机电致发光器件. 器件性能随发光层厚度变化而变. 在DPVBi厚度为10---50 nm范围内, 同样电流密度下器件亮度及效率随DPVBi厚度增加先增后减, 40 nm时最佳, 最高亮度达到15840 cd/m², 最高外量子效率达到3.2%, 器件色坐标(Commission Internationale de l'Eclairage (CIE) co-ordinates) 为(0.15, 0.15). DPVBi厚度超过40 nm时器件发光光谱出现红移而致色度变差, 其原因可归于微腔效应所致. 同时, 通过实验结果分析表明DPVBi中激子扩散长度位于20---30 nm范围.     

一种白光有机电致发光器件的制备

通过对器件结构的优化设计，提高了白光电致发光器件中蓝光成分的发光效率，从而得到了一种较为理想的有机白光电致发光器件。驱动电压为5V时，电流密度J=0．5mA／cm^2，器件的效率达到最大，流明效率为1．92 lm／W，此时器件的发光亮度接近20cd／m^2。色坐标为(x=O．317，y=0．328)。非常接近白光等能点．是色度很好的白光。并且在很大范围内，色度随器件的驱动电压或电流变化不大，当驱动电压变化至15V时。f=232mA／cm^2，色坐标变化至(x=0．338，y=O．353)。在电压为22V时，器件的亮度达到最大，为17 000cd／m^2。此外器件结构相对简单。器件制备的可重复性得到很大程度的改善。     

稳定的光谱不随电流变化而改变的白色有机发光器件

使用新材料构成了两种结构白色有机薄膜电致发光器件，一种是蓝色及红色发射在同一层中，另一种是蓝色发射和红色发射分别在两层中，器件结构分别为ITO／CuPc／NPB／JBEM（P）：DCJT／Alq／MgAg（器件1）和ITO／CuPc／NPB／JBEM（P）／Alq：DCJT／Alq／MgAg（器件2）。这里（CuPc）是空穴注入层；N，N’－bis－（1－naphthyl）－N，N’－diphenyl－1，1’bipheny1－4－4’－diamine（NPB）是空穴传输层（HTL）；9，10－bis（3’5’－diaryl）phenyl anthracene（JBEM）是蓝色发射层；tris（8－quinolinolato）aluminium complex（Alq）是电子传输层（ETL）；DCJT是红色染料。在器件1中得到稳定的且色度不随电流增在而变化的白色发射。它的最大亮度为14850cd/m^2，最大效率2．88lm/W，色度x＝0．31，y＝0．38（从4mA/cm^2到200mA/cm^2），半亮度寿命为2860小时（初始亮度1000cd/m^2）。比较了两种结构的器件，蓝红色发射在同一层结构的器件，在亮度、效率及稳定性上都优于蓝红发射在不同层结构的器件。     

高效率高亮度红色有机电致磷光器件

在一种红色有机电致磷光器件中采用双(2-甲基-8-喹啉)4-联本氧基铝[bis(2-methyl-8-quinolinato)4-phenylphenoJate aluminum,BAlq]为空穴和激子阻挡层,得到了效率、亮度和色度俱佳的发光器件。器件最高亮度为10362cd／m^2,最高外量子效率为7．0％,器件色坐标[Commission Internationale de l’Eclairage(C1E)coordinates]为(0．672,0．321)。另外在大电流密度100mA／cm^2下,量子效率仍有4．3％。该器件性能指标基本能够满足彩色动态显示中对红色发光的要求。     

两种蓝色有机电致发光材料

重点研究以两种蓝色OEL材料蒽类衍生物JBEM和联苯乙烯衍生物DPVBi分别作基质，以perylene作掺杂剂的器件的电致发光性能，特别研究了它稳定性，在这度和效率方面，两种器件并没有很大差别，然而在稳定性方面却有很大差别，蒽类衍生物JBEM的器件在100cd/m^2初始亮度下，半亮度寿命可达1035h，而DPVBi的器件在同样条件下，半亮度寿命为255h。通过分析两种器件的能级图，认为稳定性的差别可能源于两种蓝光材料本身的热稳定性不同，JBEM优于DPVBi，是一种很有前途的蓝色发光材料。     

两种不同结构的蓝色有机发光二极管

制备了两种不同结构的蓝色发光器件。其中阻挡层结构的器件为：ITO／CuPc/NPB/TPBi/Alq/MgAg;夹心型结构的器件为：ITO／CuPc/NPB/DPVBi:perylene/Alq/MgAg。两种器件的发射光谱分别为NPB和perylene的特征光谱,最高亮度和最大效率分别为3700cd/cm^2、6123cd/cm^2和0.781m/W,0.831m/W。然而,两种器件稳定性差异较大。用能级结构图分析了两种器件的发光特性和稳定性差异的原因。     

发光效率及稳定性改善的有机薄膜电致发光器件

不久前,我们报导了以TPD为空穴传输层,Alq为电子传输兼发光层的双层薄膜电致发光器件,在定电流密度6mA/cm2连续驱动下,初始亮度106cd/m2下降至一半亮度的时间为120小时,而继续操作500小时,亮度仍有38cd/m2[1]。在这篇文章中,我们将报道一个在上述器件的空穴传输层TPD中掺杂而构成的新器件。这个新器件发光亮度和效率比原器件增加了50%,而稳定性增加了近10倍,初始亮度165cd/m2的半亮度寿命达1200小时。     

一种利用双发光区的有机红光电致发光器件

针对一般掺杂结构的红光有机电致发光器件效率随外加电压的增加而迅速下降。同时色度逐渐变差的特点,我们引入了在NPB层和Alq3层内同时掺杂DCJTB的具有双发光区的器件结构。制备的双发光区掺杂器件在驱动电压8—20V内发光效率只下降了4％;而色度从8V时的(x=0．6287,y=0．3663)变化到20V时的(x=0．6075,y=0．3841);器件的发光亮度从8V时的178cd／m^2变化到20V时的5962cd／m^2,具有较好的性能水平。观察到器件效率基本上不依赖于外加电压的变化而变化的特性,同时器件也保持一个比较好的色纯度,并对结果进行了分析。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.     

Fiber Modal Index Measurements Based on Fiber Gratings

A novel method based on fiber gratings for measuring the effective indices of fiber modes is proposed. The effective index difference between the core mode and a cladding mode was obtained by analyzing the interference fringe of a pair of cascaded long-period fiber gratings. In order to extract the core mode index from the measured index difference, an index matching oil immersion method is proposed. By analyzing the interaction between the cladding mode and the oil applied on the cladding surface, the mode order and the effective index of the involved cladding mode might be calculated. Experimental results about the interference fringe shifts induced by the oil index and the oil-applied length are also presented.     

Optical Pulse Compression Schemes That Use Nonlinear Bragg Gratings

Nonlinear optical pulse compression of picosecond pulses typically requires long lengths of optical fiber and multiple components. Periodic structures, such as fiber Bragg gratings, are highly dispersive at wavelengths outside of the photonic bandgap. This implies that such gratings can be used as very short all-fiber compressors. In this paper a number of such compression schemes are reviewed involving uniform and nonuniform fiber Bragg gratings, relying on both soliton and nonsoliton compression principles. Experimental results supporting the corresponding underlying theory are also presented. Finally, an extension of one of the compression schemes is shown, which allows the generation of adjustable high-repetition rate soliton trains.