二維光子晶體感測器之折射能帶分析

Abstract

近年來隨著科技以及網路的發展，物聯網(IOT)逐漸興起，穿戴式裝置以及建構物聯網之感測器需求也隨之越來越大。其中的智慧健康照護以及床邊檢測的應用因具有提前預防並能夠提供醫生精確的資訊做出即時判斷，也越來越受重視。對於各種病毒或者抗體抗原的檢測，最重要的就是生物感測器的部份，其成為一個好的感測器有極高的靈敏度以及極低的量測極限是必備的。因此本篇論文提出一種創新概念的光學量測方法應用於折射率偵測，並且得到超越許多先前生物感測器文獻報告的元件效能。 在第一部分的研究中，我們展示了一個具有高靈敏度、微型量測系統的二維光子晶體感測器。我們所設計的六角週期排列光子晶體，能夠在空間中將光束衍射到不同的角度平面，並且利用位於滿足項為匹配方程式與成為消逝波之間的臨界波長來判別施加在元件表面待測物的濃度折射率變化。本實驗中使用葡萄糖作為量測對象，我們的感測器呈現對於折射率變化有極高的敏感度以及極低的測量極限，我們的量測系統的靈敏度能使每單位折射率產生3091奈米的波長變化，並且葡萄糖解析濃度達到0.1mM，一般人體中血糖的正常範圍是4 ~ 7 mM，結果顯示我們已經可以應用於偵測臨床糖尿病患者的血糖含量。 接下來，在第二部分中我們為了更進一步的提升元件效能，我們將光子晶體獨特衍射光學特性與波導模態共振結合，在元件上沉積一層氮化矽薄膜作為導通層，進而將特定波長的光侷限在導通層，在衍射光的頻譜圖上可以觀測到某個波段會有強度下降的現象，此為滿足項為匹配方程式以及滿足於波導的解的結果，因此此現象會對折射率變化更加敏感。在量測的部分也呈現了靈敏度的提升以及更低的量測極限，此元件的靈敏度可以達到每單位折射率產生9173.88奈米的波長變化，且葡萄糖的量測極限達到0.01mM，量測極限範圍達到 〖10〗^(-8) 至 〖10〗^(-9) 的折射率變化，我們的研究結果展示了我們所設計的元件結構以及光學量測分析是非常具有淺力應用於生物感測器當中。

With the developments of technology and the internet, Internet of Things (IOT) become more and more popular, wearable device and various of sensor which construct the IOT have tremendous demand. Developing smart health care and the point of care testing (POCT) application are also getting more and more attention because it can prevent the diseases and provide doctors with accurate information to make the correct diagnosis. For the detection of various viruses or antibody antigens, the most important part is the biosensor, which have the high sensitivity and the extremely low limit of detection. Therefore, this thesis proposes an innovative concept of optical measurement for the detection of the refractive index, and the performance of our device already exceed the previous reports of other biosensor. In the first part, we demonstrate a hexagonal photonic crystal (PhC) biosensor with high sensitivity and compact measurement system. The PhCs are able to diffract optical beams to various angles in the azimuthal space. The critical wavelength that satisfies the phase matching or becomes evanescent is employed to benchmark the refractive index of analyte on the sensor surface. Using goucose solution as the analyte, our sensor demonstrates very high sensitivity and low limits of detection (LOD). The sensitivity of our measurement is calculated to be 3091 nm/RIU and the LOD is 0.1 mM, and the normal range of blood sugar in the human body is 4 ~ 7 mM. The result shows our sensor is capable of detecting clinical cut-off blood sugar for Diabetes patients. We next integrated the unique optical diffractive properties of 2D PhCs with guided mode resonance in order to further improve the performance of the sensor. The sensor was deposited with a SiNx layer as the guiding layer for confining the light of the specific wavelength. In the spectra of the diffraction beam, we can observe it has a dip in the specific wavelength. This is the results of satisfying the phase matching condition and being a solution of the waveguide’s equations. Thus, this phenomenon is more sensitive to the changes of the refractive index. In the measurement, it also shows an increase in sensitivity and a lower LOD. The sensitivity of measurement system was calculated to be 9173.88 nm/RIU and the limit of detection was 0.01 mM. The range of the limit of detection in our experiment is from 〖10〗^(-8) to 〖10〗^(-9) (RIU). We are quite confident that our device has great performance of biosensor for real-time, label-free, rapid detection.