Cost-effective and dispersion-tolerant cascade modulation for millimeter-wave-over-fiber applications

In millimeter-wave-over-fiber (MWoF) feeder systems, the received millimeter-wave signals at the remote antennas (RAs) can suffer from signal fading by chromatic dispersion of optical fiber. This can be substantially mitigated by Mach-Zehnder modulator (MZM) based photonic up-conversion technique. In this technique, the data signals at intermediate frequency (IF) are frequency up-converted to millimeter-wave frequency by an MZM biased at its transmission null point. However, this scheme requires a costly, high-speed MZM, which will hinder the widespread of this technique for cost-sensitive MWoF applications. Hence, we propose and demonstrate a cost-effective way of reducing the cost of MWoF optical transmitters based on photonic up-conversion technique. We employ a dual wavelength source composed of a directly modulated laser and a polarimetric filter. This source is used to generate a millimeter-wave tone signal and to frequency up-convert the IF data signals to millimeter-wave frequency. The dual wavelength source is also shared with numerous RAs for further cost reduction. Our experimental demonstration performed with 30 Msymbol/s 16-quadrature amplitude modulation signals shows that we can transmit the 20 GHz millimeter-wave signals over 25 km standard single-mode fiber without any transmission penalty.     

掺Er~(3+)的氟氧化物微晶玻璃上转换及近红外光谱性质

研究了组份为46SiO2-46PbF2-5Al2O3-3ZnF2(mol%),外掺4ErF3(mol%)的氟氧化物玻璃样品在微晶化前后的性能。根据样品的DTA曲线分析了其热稳定性,测试了微晶化前后Er3+的吸收光谱、上转换及近红外荧光光谱,根据样品的XRD图谱对比得到了其微晶相PbF2。结合能级图和荧光光谱分析了微晶化对光谱性质的影响。研究表明,微晶化后上转换荧光强度得到了极大的提高,特别对667nm的红光,其作用更为明显,微晶化对1.5μm荧光的有效半高宽几乎没有影响,但却极大地削减了峰值发射截面,显著地减小了Δλeff×eδ。     

溶胶-凝胶制备ZnO-SiO2复合膜的量子效应和上转换发光

采用溶胶-凝胶技术在玻璃衬底上制备了ZnO薄膜和ZnO-SiO₂复合膜.原子力显微镜照片显示ZnO薄膜具有球状纳米晶粒;可见光-紫外透射光谱表明ZnO-SiO₂复合膜在可见光区的透过率大约是85%,透过率从330 nm开始下降,到290 nm附近降为零.由于量子效应,吸收边出现明显的蓝移.在室温下用不同波长的光激发ZnO-SiO₂复合膜,光致发光谱显示ZnO-SiO₂复合膜对应于激子发射的290 nm附近的紫外发光峰与透射谱所显示的吸收边位置一致,没有出现斯托克斯红移.同时,ZnO-SiO₂复合膜出现了双光子和三光子吸收现象和上转换发光现象. 关键词： 2')" href="#">ZnO-SiO₂ 量子效应 双光子和三光子吸收 上转换发光     

Preparation of NaYF4:,Er3+/TiO2 composite and up-conversion luminescence properties under visible light excitation

The up-conversion luminescence composite NaYF 4:Er 3+ /TiO 2 is prepared using the sol-gel method.The specimen has good crystallinity and two shapes,i.e.,viereck and round,while the sizes of viereck and round particles are both micron-sized.The TiO 2 has an anatase structure,while the NaYF 4 has a hexagonal phase,which can be hardly obtained through the common sol-gel method.Due to the big particle size and the high crystallinity of pure NaYF 4:Er 3+,the composite has a small specific surface area that is less than Degussa P25 TiO 2.The NaYF 4:Er 3+ /TiO 2 composite shows several emission peaks at 211,237,and 251 nm under the excitation of 388 nm,at 395 nm and 411 nm under the excitation of 500 nm,and at 467,481,492,and 508 nm under the excitation of 570 nm.     

稀土离子的上转换敏化发光

选择合适的稀土离子敏化是提高上转换发光效率的最有效途径之一。本文总结了在玻璃中常见的稀土元素敏化离子对在不同泵浦方式下的发光方式,并讨论了稀土离子间的敏化发光的研究前景。     

Gd3+,Yb3+和Tm3+共掺杂氟化物纳米晶中Yb3+-Tm3+-Gd3+间的能量传递

用水热法合成了Y_0.8-x-yF₃∶Gd_x³⁺,Yb_0.2³⁺,Tm_y³⁺纳米晶的上转换发光材料。在典型的Y_0.595F₃∶Gd_0.200³⁺,Yb_0.200³⁺, Tm_0.005³⁺纳米微晶中,在980 nm激光激发下,观察到了Tm³⁺的紫外、紫色上转换发射明显增强和来自于Gd³⁺的⁶D_9/2、⁶I_J、⁶P_5/2及⁶P_7/2能级到基态⁸S_7/2能级的紫外发射。通过比较Y_0.8-x-yF₃∶Gd_x³⁺ ,Yb_0.2³⁺,Tm_y³⁺纳米晶样品的上转换发光性质以及Tm³⁺和Gd³⁺中一些激发态的能级寿命,借助于能级图描述了Yb³⁺-Tm³⁺-Ga³⁺之间的有效的能量传递过程。     

提高能量上转换效率的实验探讨

通过以TeO₂,GeO₂,ZnF₂,SiO₂,PbF₂等为主体的氟氧化物玻璃陶瓷基质材料的研究提出了提高上转换效率的某些条件.选择低声子能量的基质,且基质的M系数接近稀土离子的M系数的氟氧化物基质材料是高效上转材料的基础,选择激发光光子能量与稀土离子、敏化稀土离子能级匹配是高效上转换材料的必要条件.为设计研究稀土掺杂能量上转换材料提供了有理论和应用价值的结果. 关键词： 能量上转换 氟氧化物玻璃陶瓷 稀土掺杂     

BLUE COOPERATIVE UP-CONVERSION LUMINESCENCE OF Yb3+ IONS IN OXYFLUORIDE GLASS EXCITED BY 960 nm LASER

Investigates the up-conversion luminescence of Yb-doped oxyfluoride glass excited by a 960nm-diode laser. A new up-conversion cooperative radiation luminescence is found, which is rather strong and positioned at 476.1 nm. It comes from the coupled states of two-Yb^{3+-ions cluster. It is significant because it is an effective and convenient method of producing blue light.}     

CaF2：xYb3+, yEr3+纳米颗粒的合成及其上转换发光性质

采用水热合成法制备了CaF₂：xYb³⁺,yEr³⁺（x=0.1~0.8,y=0.01~0.08）纳米颗粒,利用X射线粉末衍射仪、透射电子显微镜和F-4600荧光分光光度计表征了样品的物相和形貌尺寸,并探究了Yb³⁺和Er³⁺掺杂浓度对样品的上转换发光性质的影响。结果表明,所合成的样品为立方相,球形颗粒,平均直径为 12 nm,敏化剂Yb³⁺的最佳掺杂摩尔分数为20%,而激活剂Er³⁺的最佳掺杂摩尔分数为6%。此时,绿光与红光的强度之比最大。     

Er3+浓度对Er3+/Yb3+共掺氟氧化物玻璃陶瓷上下转换发光的调控

在980 nm激光激发下,Er³⁺/Yb³⁺共掺的发光材料既可以在可见光范围产生上转换发光,也可以在近红外波段产生下转换发光,二者存在竞争关系。本文利用熔融淬火法制备了一系列掺杂不同Er³⁺/Yb³⁺浓度的氟氧化物玻璃陶瓷,测量了样品在980 nm激光激发下的上转换及下转换发射光谱。研究发现,改变Er³⁺的掺杂浓度可以调控上下转换的发光强度。在此基础上,提出了上下转换发光的能量传递模型。本文的研究结果有利于该类材料在不同领域中的应用。