输出红光的电子俘获材料及其在图像存储和减法中的应用

研究了输出红光的电子俘材料的光学性质和物理机制。利用－２００μｍ厚的电子俘获薄膜在实验上证明了图像存储和图像减法的可能性。实验表明，这种材料对光存储和光学信息处理应用，具有很多有吸引力的优点，如：可擦除，可重写，高分辨，高速度，以及模拟和并行操作等。     

电子俘获型红外上转换屏

利用溶液悬浮分层提取技术获得粒度较为一致的电子俘获材料（ＥＴＭ）粉末，考虑ＥＴＭ屏空间分辨率、红外→可见发光亮度、ＥＴＭ化学稳定性和膜层均匀性等主要因素，采用不同方法制作了ＥＴＭ屏，较好地解决了ＥＴＭ膜层均匀性及器件封装后的化学稳定性等问题，并通过测试比较，提出了一种兼顾空间分辨率和红外上转换发光亮度的微镶嵌屏制作技术方案．     

电子俘获材料的光学性质及光存储机制研究

报道在硫化锶中掺入Ｅｕ、Ｓｍ和Ｃｅ、Ｓｍ两种激活剂的具有良好的光存储功能的新型光子学材料。以紫外到绿光之间不同波长的光写入信息，用近红外光读出，读出信号为橙色或绿色发光。系统的光响应速率小于２０ｎｓ，写／读／擦速度快；光存储机制为电子的俘获和释放，无热效应，比目前的其他光存贮系统更优越。     

电子俘获材料的红外上转换效率

采用稀土直接掺杂工艺提高了电子俘获材料CaS:Eu,Sm和CaS:Ce,Sm的发光亮度和制备效率,并利用超短脉冲红外激光测试了它们的红外上转换效率.借助等离子体质谱技术检测了硫化助熔剂法和稀土直接掺杂工艺合成电子俘获材料中主要掺杂剂的化学计量比,分析了影响电子俘获材料上转换发光效率的主要因素.     

高效的红外到可见上转换氟氧化物玻璃材料

本文报道了一种高效的Ｅｒ＾３＋掺杂红外到可见的上转换氟氧化物玻璃材料。材料的组份为６０ＴｅＯ２－８ＰｂＦ２－１０ＡｌＦ３－１０ＢａＦ２－１０ＮａＦ－２ＥｒＯ３／２,给出了样品的制血方法。测量了该材料在室温下的吸收光谱,在８０８和９７０ｎｍＬＤ激发下观察到了非常强的上转换荧光,测量了在不同激发波长激发下Ｅｒ＾３＋的绿色荧光,讨论了在８０８和９７０ｎｍ激发下上转换发光的机理。测量了上转换发射光谱,研     

蓝光LED激发深紫外上转换发光材料的光学定位与追踪应用

光发射波长小于320nm的深紫外发光材料具有光子能量高和不受室内环境光干扰等特性,在光化学与光医学领域具有重要应用前景,近年来受到国内外学者的广泛关注。本文利用固相合成法制备了Pr³⁺单掺和Pr³⁺⁃Gd³⁺共掺的LiYSiO₄∶Pr³⁺和Li（Y,Gd）SiO₄∶Pr³⁺深紫外上转换发光材料。在450nm蓝光（激光或LED）激发下分别实现了C区紫外和窄带B区紫外上转换发光,发光峰值分别位于280nm和313nm。系统研究了蓝光激发功率对深紫外上转换发光性能的影响规律,证实了蓝光激发下的双光子上转换发光物理机制。探索利用LiYSiO₄∶Pr³⁺作为光转换层,以蓝光LED作为激发源,设计构筑了新型荧光转换型UVC光源,并展示了该光源在室外光学定位与追踪领域的应用。     

Yb3+和Er3+共掺杂氟硼酸盐玻璃材料光学跃迁及红外到可见上转换

利用Ｊ－Ｏ理论和吸收光谱实验数据计算了Ｅｒ＾３＋掺杂的氟硼酸盐玻璃材料的光学跃迁参数,从而得到了一些能级间跃迁的振子强度、跃迁几率、分支比、及寿命等数据。在室温下观察到了在９７０ｎｍＬＤ激发下红色和绿色上转换发光,讨论了红色上转换发光强度与ＬＤ电流的关系。     

Tm3+掺杂锗酸盐玻璃材料上转换发光的研究

测量了50GeO₂-40PbF₂-9.9WO₃-0.1Tm₂O₃玻璃材料的Raman光谱。确定了Tm³⁺离子在这种材料中¹G₄上转换发射的有效激发波长为650nm,并且观测了在650nm激发下Tm³⁺的¹G₄上转换发光及其斜率效率。采用ASE(Amplified Spontaneous Emission)技术测量了⁴G₄上转换发射的光学增益系数。     

方波激发下Er3+上转换绿光发光动力学过程的研究

用方波电源驱动808 nm,980 nm激光二极管(LD)激发Er3+掺杂的亚碲酸盐氟氧化物玻璃,测量2H11/2,4S3/2能级上转换发光的上升和衰减,不同波长激发下的上升时间常数不同,说明808 nm LD和980 nm LD激发下2H11/2,4S3/2能级上转换激发途径不同.通过建立速率方程模型分析了4S3/2能级的上升特性与中间能级寿命的关系,从而确定了两种波长激发下上转换绿光的激发机理.     

稀土离子的上转换发光及研究进展

稀土离子的上转换发光由于其在短波长激光器方面的潜在应用而受到了广泛的重视,本文总结了稀土离子中常见的几种不同的发光机制,分析了几种常见稀土离子在不同的泵浦方式下的发光方式,讨论了稀土离子上转换发光对基质成分的依赖性及其研究进展,并对稀土离子上转换发光的研究及应用进行了展望。     

基于多参考点的X线双能量减影算法

提出了不直接依赖于入射X线强度的基于多参考点的双能量减影算法.该算法选取图像中的若干个像素点作为参考点,在对这些参考点进行平滑处理后分别求解双能量方程以产生多幅具有相同纹理的减影图像,将这些图像进行平均后得到保留着动态信息的骨骼和软组织图像.该算法将减影和滤波过程同时进行,提高了结果图像的质量.实验表明该算法具有较强的稳定性,实现了计算机自动处理.     

Flat-top ultra-wideband photonic filters based on mutual coherence function synthesis

A novel all-incoherent optical circuit that allows for band-pass microwave-photonic filter design is presented and verified through numerical simulation. In contrast to conventional spectrum-sliced optical architectures that operate on the basis of a finite number of discrete taps, our proposal is based on arbitrary shaping of the spectrum of the broadband optical source in a conventional frequency encoder. This fact dramatically increases the free spectral range of the filter with respect to the conventional discrete-time optical processing. The filter transfer function is given by the mutual coherence function of the filtered source which allows, through an inverse problem, sculpting the RF filter response. The effect of higher-order dispersion terms is also included by means of the optical coherence theory. Finally, some strategies are provided in order to alleviate the baseband resonance constraint. Numerical results are also included.     

Edge linking and image segmentation by combining optical and digital methods

We present a hybrid method for segmentation of intensity images, which combines an optical contouring technique and digital algorithms for linking edge points or image segmentation. In a first stage, the digital image to be processed is displayed in a twisted-nematic liquid-crystal display (LCD), which is placed between a polarizer–analyzer pair at 45 deg (instead of 90 deg as occurs in standard LCDs). It is not difficult to demonstrate that the proposed setup produces a resultant image with very pronounced dark contours at middle intensity. After the optical preprocessing, two different digital algorithms are applied: an edge linking algorithm (modified chain code) and a simple thresholding technique for image segmentation. The proposed procedure works well with monochromatic and color images. The method could be useful as a robust technique for segmentation of large images in real-time, which presents potential applications in medical and biological imaging.     

Extraction of difference of two images using periodic carrier modulation

The optical method of extraction of difference between transparencies using periodic carrier modulation was first proposed and successfully demonstrated by Pennington. His method was based on the modulation of each of the image transparencies by the same grating with the difference that one modulating carrier was shifted by half-period with respect to the other. In order to ensure extraction of difference signal from unwanted sum signal, the modulating carrier frequency must be too low. This poses a serious problem because shifting a high frequency grating exactly by a half-period is not an easy task. In order to surmount this difficulty Belvaux and Lowenthal proposed that instead of using a grating, the images transparencies can be modulated by fringes obtained in a Wollaston prism. It is well-known that these fringes can be shifted by a half-period by rotating an analyzer at the output side by 90°. The optical methods of subtraction of images suffer from the disadvantage that the photographic record has to be developed and fixed by wet processes. The processed record is then Fourier transformed and suitably filtered to extract the difference signal. In the present paper we have carried out extraction of difference of two images using the principle of periodic carrier modulation by carrying out spatial frequency filtering of the total irradiance distribution numerically. Some of the results of subtraction are presented.     

Novel 160-GHz wavelength converter based on a SOA and a long period grating

The proposed converter is based on cross-phase modulation (XPM) in a semiconductor optical amplifier (SOA). The predominantly phase-encoded signal at the SOA output is converted to a purely amplitude-modulated signal using a long period grating. First, we design the converter in terms of power conversion efficiency and pulse pedestal suppression. Subsequent analysis for the delayed-interference signal-wavelength converter (DISC) revealed that our device offers 5 dB higher power conversion efficiency and gives shorter pulses at the converter output. In the proof-of-principle experiment, good agreement with the theoretical predictions is obtained.     

Simple optical preprocessing for optical clock recovery using a single fiber Bragg grating filter

We propose a simple optical preprocessing for optical clock recovery using a fiber Bragg grating (FBG) filter. In the proposed scheme, the signal preprocessing is performed by suppressing the carrier component through the FBG filter, and experiment shows that the clock component is larger than about 10 dB compared with other rf components within a distance of from the clock frequency component.     

共焦光学传感头用于红外上转换油墨的微弱光检测

提出了采用共焦光学传感头检测红外上转换油墨(IRink)的上转换弱光信号的方法,采用了专门设计的光学元件和检测放大电路,实现了红外油墨上转换发光的微弱光检测,对不同混合比例红外上转换油墨进行了检测,分析了实验结果.其结构简单、取样准确,可实现探测器的袖珍化.     

Partially coherent optical processor for enhancement of partial second order derivatives of an image: Analysis and implementation

We present an optical processor capable to perform partial second derivatives of an image working with partially coherent illumination. The proposed system utilizes a liquid crystal display, onto which images to be derived are displayed. The method is based on the capacity of these devices to generate simultaneously a contrast reverted replica of the image displayed on it. A positive replica of original image is obtained when the LCD is between crossed polarizers, while the negative one is obtained with the LCD is between parallel polarizers. Since the LCD is a diffraction element, both polarizer arrangements may be simultaneously implemented, for example, in a 4f optical processor using polarization filtering of the different diffraction orders. When three images (two replicas of original image displaced in opposite direction and the other one with contrast reverted and centered at the origin.) are imagined across a slightly defocused plane, one obtains an image with enhanced second derivatives in a given direction. No other incoherent (or partially coherent) optical system is presently known which can perform partial second-order derivatives of an image. Experimental results obtained are presented.     

All-optical demultiplexing of 4-ASK optical signals with four-wave mixing optical gates

A new all-optical technique to demultiplex quaternary-amplitude-shift keying (4-ASK) signals into two on-off keying (OOK) signals is proposed. We show that such quaternary-to-binary conversion may be performed with two types of optical gates (OGs); a first one that implements an S-shaped optical power transfer function (TF), which is also the characteristic TF of optical pulse reshaping devices, and a second type that implements a U-shaped TF. Furthermore, we describe a heuristic approach to design such OGs by using the fiber four-wave mixing effect in highly non-linear dispersion-shifted fibers. The performance of the technique is evaluated by simulating the demultiplexing of 4-ASK signals with these OGs. Results indicate that the proposed devices are able to provide binary signals with acceptable BERs even after the 4-ASK signals are propagated through a cascade of eight fiber links of 50 km followed by optical amplifiers with a 4.5-dB noise figure.