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991.
In this work, we study the effect of concentration, host medium, PH and phase states on the fluorescence emission from the
laser dye Rhodamine B pumped by UV laser as exited source. The polymethylmethacrylate PMMA is used as a host medium in case
of solid phase samples while, ethanol and Tetrahydrofuran (THF) are used in case of a liquid one. Laser Induced Fluorescence
(LIF) technique was used to study the fluorescence properties of both cases of liquid and thin film solid-state samples. In
addition, the Dual Thermal Lens (DTL) technique was used to study the quantum yield of these samples. The concentrations of
Rhodamine B in ethanol as solvent between 2 × 10−2 M and 5 × 10−6 M were studied. The maximum fluorescence emission is observed at concentration of Rhodamine B C = 3 × 10−4 M. Comparison studies were investigated for different host medium such as ethanol, THF, PMMA in liquid phase state and PMMA
in solid phase state. The measurements revealed that, the behavior of both phases state was analogous. Rhodamine B/PMMA thin
film sample by ratio of 4:1 and thickness 0.12 mm was found to have the best photostability sample with a quantum yield about
≈0.82. 相似文献
992.
A new type of comb frequency filter based on one-dimensional photonic crystals (1DPC) containing two kinds of single-negative-refractive
media is presented. The filter is a multichannel one with the number of channels being dependent on the number of 1DPC periods.
The position of each channel and its Q value can be adjusted varying the thickness of the material layers. 相似文献
993.
M. A. Geday D. P. Medialdea B. Cerrolaza N. Bennis X. Quintana J. M. Otón 《Opto-Electronics Review》2009,17(2):140-143
The ferroelectric-antiferroelectric transition in greyscale generation of antiferroelectric liquid crystal displays (AFLC)
is a heterogeneous process. The process has been described as the growth of finger-like domains [1]. We have previously studied
the ferroelectric-antiferroelectric phase transition, relaxation that follows the data pulse in surface stabilized asymmetric
antiferroelectric liquid crystal displays using biasless video frequency waveforms [2]. This relaxation involves an intensity
decay of the light transmitted by a pixel and depends on several parameters such as surface stabilization, rotational viscosity
of the AFLC, magnitude of the data pulse, and bias voltage.
The usual multiplexed driving of AFLC displays leads to long-term stabilisation of the grey levels induced by the data pulses
within the selection time. However, depending on the bias level, alternative greyscale mechanisms may be obtained by allowing
the grey levels to decay during the frametime. These greyscales may be advantageous in some instances since they improve the
dynamic response of the AFLC device and reduce the reset time of the waveform.
In this study we extend the previous work to include the effect of bias. We present the measured data, in terms of growth
pattern and speed and present an extension of the previously model on order to explain the results. 相似文献
994.
A nonlocal Euler–Bernoulli elastic beam model is developed for the vibration and instability of tubular micro- and nano-beams conveying fluid using the theory of nonlocal elasticity. Based on the Newtonian method, the equation of motion is derived, in which the effect of small length scale is incorporated. With this nonlocal beam model, the natural frequencies and critical flow velocities for the case of simply supported system and for the case of cantilevered system are obtained. The effect of small length scale (i.e., the nonlocal parameter) on the properties of vibrations is discussed. It is demonstrated that the natural frequencies are generally decreased with increasing values of nonlocal parameter, both for the supported and cantilevered systems. More significantly, the effect of small length scale on the critical flow velocities is visible for fluid-conveying beams with nano-scale length; however, this effect may be neglected for micro-beams conveying fluid. 相似文献
995.
996.
研究了GaN/AlGaN异质结构中的双带(中、远)红外探测及光子频率上转换特性.通过光致发光光谱确认GaN/AlGaN探测器结构中AlGaN本征层的Al组分,讨论了不同Al组分GaN/AlGaN异质结的导带带阶界面功函数差.在拟合单周期GaN/AlGaN探测器中红外和远红外波段响应谱的基础上,研究多周期GaN/AlGaN探测器与GaN/AlGaN发光二极管集成结构的中红外和远红外光子频率上转换效率与GaN发射层厚度、AlGaN本征层厚度、紫光光子出射效率、内量子效率、空间频率和发射层掺杂浓度间的关系,优化
关键词:
双带红外探测
光子频率上转换
响应谱
GaN/AlGaN 相似文献
997.
998.
分析了浅海甚低频声场中的垂直双水听器的互谱特性,尤其关注了声场中只存在两阶简正波时声压互谱的有功分量.数值计算表明:当两个水听器的深度布放合理时,声压互谱有功分量的正负号分布与水平距离无关,选择合适的水听器深度布放组合,可以用于水面目标、水下目标的双择判决;声速分布对该方法的使用影响不大,海底存在吸收将影响算法的作用距离,但在有效作用距离内,该算法仍有较好的稳健性.运用Pekeris波导有效深度的概念建立了声压互谱有功分量正负号分布特性的近似理论分析并可预报双水听器合理的布放深度.理论分析揭示了双水听器布放深度之和应等于波导有效深度,并且在有效深度限制的波导范围内,整个声场的声压互谱有功分量的正负号分布被分为三个水平区域.理论分析加深了对浅海低频声场特性的理解,对该算法的实际使用有指导意义.
关键词:
目标深度分类
浅海低频声场
声压互谱
有功分量 相似文献
999.
1000.
报道了一种LD端面抽运Nd:YAG陶瓷、KTP腔内倍频的全固态连续波绿光激光器.当抽运功率为21.6 W时,1064 nm基频输出达到11.3 W,光—光转换效率为52.3%.采用Ⅱ类切割的KTP晶体作为腔内倍频介质,在直腔结构下获得了最大功率为1.86 W的532 nm绿光输出,光—光转换效率为7%.输出光斑具有高斯型强度分布,1 W输出时的M2因子约为1.7.
关键词:
全固态绿光激光器
Nd:YAG陶瓷
KTP倍频
直腔 相似文献