Analysis of Diffraction Band Diagrams of a Two-dimensional Photonic Crystal Sensor

• Main Authors: Chien-Chun Chen, 陳建均
• Other Authors: Jian-Jang Huang
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/9t5cq3

碩士 === 國立臺灣大學 === 光電工程學研究所 === 106 === 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.