【作者】 张萌；

【导师】 王鹏飞；

【作者基本信息】 哈尔滨工程大学 ， 光学工程， 2023， 博士

【摘要】 稀土离子具有丰富的能级结构,在泵浦光的激励下,可以产生紫外-可见-红外超宽光谱范围内的跃迁吸收和荧光辐射,因而稀土离子掺杂玻璃材料被广泛的应用在激光器、放大器、光通讯等诸多领域。随着微纳加工技术的提升,可以通过激光熔融等多种方法制备稀土离子掺杂玻璃微球,将传统回音壁模式微腔体积小、易集成的特点与稀土离子掺杂材料优异的光致发光特性相结合,进一步拓展了稀土掺杂玻璃材料的应用领域。然而目前绝大多数都采取近场耦合方式实现对稀土掺杂微球的激发,暴露在空气中的耦合系统稳定性差、易受测试环境参数的影响,难以应用在复杂多变的实际场景中。因此,本论文旨在提出一种新型的稀土掺杂微球耦合和封装方式,制备基于稀土掺杂微球的集成结构,并对其光学特性进行分析,对其在光学传感领域的应用进行探索,为稀土离子掺杂玻璃材料的集成化、小型化发展提供了新的研究思路。本论文的主要研究内容如下:1.对光纤与微球耦合的基本原理以及耦合方程进行了分析和推导,设计并制备了一种三悬挂芯中空光纤,借助其内部的空气孔,完成了无源微球集成结构的制备。然后对该集成结构的传输光谱进行了测试,结果表明微球中的回音壁模式被有效激发,与其他近场耦合方式相比,该结构极大的提高了耦合系统的稳定性。2.探索了稀土离子掺杂玻璃及玻璃微球的制备工艺,分别制备了Er³⁺-Yb³⁺离子共掺锗酸盐玻璃和玻璃微球,并将微球集成在悬挂芯中空光纤内部。在980 nm激光的泵浦下,玻璃及玻璃微球均实现了可见光上转换荧光发光。通过改变Er³⁺、Yb³⁺离子的掺杂浓度以及调节980 nm激光泵浦功率大小,分别实现了对玻璃和玻璃微球集成结构的上转换发光过程的调控,其荧光发光颜色呈现明显的变化,证明该集成器件在彩色成像等领域具有一定的应用潜力。3.探索了Er³⁺-Yb³⁺离子共掺碲酸盐玻璃微球集成器件在温度传感领域中的应用。利用粉末漂浮法制备了Er³⁺-Yb³⁺离子共掺碲酸盐玻璃微球,并将微球集成在悬挂芯中空光纤内部。根据热力学统计原理,稀土离子能级上的粒子数遵循玻尔兹曼分布规律,通过测量受温度影响不同的2个热耦合能级的荧光强度比可以实现光学测温。因此,在980nm激光的泵浦下,得到了Er³⁺离子热耦合能级对应的中心波长在528 nm和549 nm的上转换发光峰。通过测量荧光强度比(I₅₂₈/I₅₄₉)与环境温度的数值关系,在300-380 K范围内,利用该器件实现了最大绝对灵敏度为38.6×10^-4 K^-1的温度传感测量。4.探索了Er³⁺-Yb³⁺离子共掺碲酸盐玻璃微球集成器件在实现水中氨浓度检测上的应用。利用980 nm激光器泵浦Er³⁺-Yb³⁺离子共掺碲酸盐玻璃微球集成器件,实现了Er³⁺离子绿色和红色上转换可见光发光。由于在碱性环境下,苯酚红指示剂的吸收峰漂移至560 nm附近,与Er³⁺离子绿色荧光发射带重叠,因此通过监测荧光强度比（I_绿/I_红）的变化可以实现对水中氨浓度的检测,检测极限为0.5 ppm,响应时间为0.2 s。本论文提出并制备了一种新型的稀土离子掺杂微球耦合结构,实现了对稀土离子掺杂玻璃微球的集成和封装。使用近红外激光泵浦该集成微球器件,特种光纤内置的稀土掺杂微球的光致发光特性被有效激发,对其上转换荧光发光进行调控可以得到明亮且丰富的荧光颜色变化,结合荧光强度比技术可以实现温度传感以及水中氨浓度检测。未来随着研究的深入,该集成器件有望在更多领域中得到应用。更多还原

【Abstract】 Due to their unique photoluminescence properties,rare-earth doped glass materials have been explored and developed for a number of traditional applications such as lasers,amplifiers and other important optical research areas.During the last few decades,based on state-of-the-art fabricating techniques,the application of micro-lasers,especially whispering-gallery mode（WGM）micro-resonator lasers,in chemical and biological sensing has increased due to advances made in reducing the gap between laboratory experiments and their real-world applications.Combining the unique properties of rare-earth doped glass with the WGM resonances make it possible to obtain light emission via rare-earth transitions at different wavelength bands.A range of further promising applications in different areas such as biology,molecular spectroscopy and environmental monitoring are feasible so far.Rare-earth doped glass based WGM microspheres can be fabricated easily and have drawn significant attention because of their added advantages compared with WGM resonators,including narrow linewidth,strong confinement,small volume and ease of integration.However,the traditional microsphere devices are usually excited by near-field coupling methods,which results the coupling system always suffers from environmental turbulence due to the poor mechanical stability.Therefore,in this thesis,a novel WGM integrated device based on the rare-earth doped microsphere embedded into suspended core hollow fiber is designed and manufactured,which makes the entire integrated device more compact and stable,compared with tapered fibre coupling method based devices.Besides,the optical properties and sensing applications of this integrated device have been characterized and investigated.Above all,the main research contents of this thesis are as follows:1.Based on the basic principle of tapered fiber-microsphere coupling system,the suspended tri-core hollow fiber（STCHF）was designed and fabricated.Thanks to the special structure of the suspended fiber cores and the air hole of the STCHF,the microsphere was mechanically placed inside the STCHF.Then the transmission spectrum of this integrated device was measured and the WGM of the microsphere was obtained.Compared with other near-field coupling methods using tapered fiber,the performance of the mechanical stability of this novel integrated device was strongly improved.2.The Er³⁺-Yb³⁺co-doped lead-germanate compound glass and glass microspheres are fabricated respectively and the compound glass microspheres were placed into the STCHF.Both the compound glass and the compound glass microspheres have shown strong up-conversion fluorescence emissions using a 980 nm pump laser.Meanwhile,the behaviors of up-conversion fluorescence of glass and glass microsphere can vary with the doping concentration ratio of Er³⁺and Yb³⁺ions and the power of the 980 nm laser.Therefore,such variations of up-conversion fluorescence of glass and glass microsphere have shown a great potential application in the area of colorful imaging.3.Based on the special 4f energy levels,rare-earth activators have been extensively adopted as temperature measurement when they are doped into appropriate hosts.In this chapter,Er³⁺-Yb³⁺co-doped tellurite glass microspheres are fabricated by the powder floating method and the samples are placed into the STCHF.Then the green luminescence emissions at 528 nm and 549 nm of the tellurite glass microsphere are obtained using a 980 nm near infrared laser excitation.And the fluorescence intensity ratio（FIR）between such two wavelengths can vary with surrounding temperature,because the ²H_11/2 and ⁴S_3/2 levels of the Er³⁺ions are thermally coupled and the transition ²H_11/2→⁴I_15/2 and ⁴S_3/2→⁴I_15/2 can be used for optical thermometry.The temperature sensing properties were studied at the temperature range of 300-380 K and the maximum sensitivity is found to be 38.6×10^-4 K^-1.4.Based on the up-conversion luminescence emissions of Er³⁺ions,the Er³⁺-Yb³⁺co-doped tellurite glass microsphere integrated inside STCHF can be used for ammonia concentration in water detection.In this chapter,Er³⁺-Yb³⁺co-doped tellurite glass microspheres are prepared and packaged inside STCHF.Under 980 nm laser pump,the green and red up-conversion visible luminescence emissions of the glass microsphere were achieved.The main absorption peak of phenol red will shift to 560 nm in alkaline environment,which overlaps with the green luminescence emission of Er³⁺ions.Therefore,the ammonia concentration in water can be detected by monitoring the change of fluorescence intensity ratio between green and red luminescence emission.The limit of detection is 0.5 ppm and the response time is 0.2 s.In this thesis,a novel integrated device consists of rare-earth doped compound glass microsphere and STCHF are investigated comprehensively.The photoluminescence properties of the rare-earth doped glass microspheres are presented using near-infrared laser excitation.Color-tunable up-conversion photoluminescence can be achieved by a number of methods,such as the co-doping ratio and the pump power.The overall results suggest that the proposed integrated device could be an exceptional choice for photoluminescence-based temperature sensing device with a good performance as well as an excellent chemical sensor with high sensitivity for the detection of ammonia concentration in water.更多还原