摘要
随着信息技术与生物工程技术的发展,生物传感器自20世纪70年代问世以来得到了迅猛发展。生物传感器不仅广泛用于传统医学领域,推动医学发展,而且还在生命科学、食品工业、环境监测等领域广泛应用。如今,人们对生活质量(如医疗卫生、环境质量、食品安全等)的要求越来越高,这推动了新探测技术的发展。结合化学表面处理技术的平面光波导倏逝波传感器就是一种新兴的技术,具有满足未来需求的潜力。本文在平面光波导平台上提出并研究了创新型的结构及新型探测技术,主要分以下几个方面：
(1)提出了并分析了基于级联双环谐振腔的传感器结构,包括一个参考环形谐振腔和一个传感环形谐振腔。第一种探测方式为基于波长探测,与传统单个环形谐振腔传感器相比,透射谱移动因为游标效应而放大,增加了灵敏度,与此同时对可调谐激光器光源的分辨率或光谱仪的分辨率要求大大降低。更进一步的,可以将透射谱的移动转换为透射谱中心双峰强度比的变化,获得更低的探测极限。将透射谱移动探测与透射谱中心双峰强度探测相结合,可以同时实现大探测范围和低探测极限。因为引入了参考环形谐振腔,温度的影响可以自动抵消,所以此传感器具有温度不敏感的优点。另外,级联双环谐振腔的传感器适合进行波分复用,满足多通道多参量探测的需求。
(2)提出并研究了基于强度探测的第二种探测方式。此种方式以低成本宽带光源作为输入光源,对光源波长及功率稳定度容差大,并且无需探测任何波长信息,仅需一个光功率计探测输出功率,与此同时仍保持很低的探测极限。此探测方式结构简单,方便易行,适合将光源和探测器集成在同一芯片上,进一步降低了成本,具有很好的实用化前景。
(3)在SOI平台上对级联双环传感器的制作工艺进行了研究。针对不同的传感探测方式制作了不同的级联双环谐振腔传感器芯片,在实验上实现了基于波长探测和基于能量探测的传感方式,验证了级联双环形谐振腔传感器的可行性。
(4)对影响级联双环谐振腔传感器基于波长或基于强度的多种探测方式工作性能的参数进行了细致的分析,全面比较了各种不同探测方式的适用原则,及各自优缺点,为级联双环传感器探测方式选择与设计给出了指导性建议。
With the development of information technology and bio-engineering techniques, the biosensor has been developing rapidly since its inception in the1970s. The biosensors are not only widely used for medical applications, but also in the field of life science, food industry, environmental monitoring and so on. Nowadays, the demand for high quality life (such as health care, environmental quality, food safety, etc.) is increasing all the time, which has driven the development of new sensing technologies. Planar waveguide evanescent field sensors combined with state-of-the-art surface modification chemistries is one such emerging technology; which has the potential to meet future demand. This thesis is mainly devoted to the study of innovative structure and new detection schemes based on planar waveguides.
We proposed and analyzed an optical waveguide sensor based on two cascaded ring resonators including a reference ring resonator and a sensing ring resonator. The first detection scheme is wavelength interrogation. The sensitivity is increased compared with a single ring resonator sensor because the transmission spectrum shift is amplified by emplying the vernier effect. At the same time the requirement for high resolution tunable laser or optical spectrummeter is decreased. Furthermore, the wavelength shift can be converted into a relative intensity variation between two cetral adjacent resonant peaks to achieve a lower detection limit. By combining the central peak wavelength interrogation with the intensity ratio detection of two central peaks, the sensor can have a large measurement range and also a very low detection limit. Since the temperature effect is automatically compensated by the reference ring, the sensor is temperature insensitive. Besides, the sensor can be operated in array format using wavelength division multiplexing as the addressing scheme.
We also studied a second detection scheme based on intensity interrogation using a low cost broadband light source. The refractive index change of an analyte can be derived from simple relative intensity measurement using a powermeter without requiring any spectral measurement. It has a large tolerance to the wavelength and power stability of the light source while the detection limit is still very low. This detection scheme is simple and easy, suitable for integration of the light sourse and photodetector in one chip with a low cost. It therefore has great potential for many practical applications.
The fabrication process of the sensor in silicon-on-insulator platform is studied and different designs of the cascaded micro-ring resonator sensors are fabricated for different detection schemes. Experimental results are demonstrated for both wavelength interrogation and intensity interrogation, confirming the superior performances of the cascaded-double-ring sensor.
The design parameters influencing the performance of the cascaded-double-ring sensor under both wavelength interrogation and intensity interrogation have been analyzed in detail. The detection limits and the optimum operation conditions of the sensors for the different interrogation schemes are analyzed and compared, providing very useful guidelines for the device design as well as for choosing the appropriate detection schemes based on application requirements.
引文
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