A grating-based plasmon biosensor utilizing phase detection to realize high resolution

利用金属光栅上的等离子体表面波激发，我们进行了研制一个折射率传感器的研究，具有超过7位数的分辨率。 理论分析结果表明：（1）采用圆锥形安装，利用模式转换伴随等离子体激元的激发，通过对反射光的效率测量，可以得到略低于6位数的分辨率;（2）如果同时采用反射光的相位检测，可以达到8位以上的分辨率。实验检测结果：（3）通过实验证实了上述（1）;（4）如果我们采用PEM（光弹性调制器）并使用零差检测，则相位检测可以达到（2）的分辨能力，因为相位检测中的仪器分辨率可以是0.1度。

Making use of plasmon surface wave excitation on a metal grating, we performed a study to develop a refractive index sensor with more than 7-digit resolution. We itemize main results of our study in theoretical analysis and in experimental inspection separately.Results in theoretical analysis: (1) If we employ conical mounting to use a mode conversion accompanying the plasmon excitation, we get a little less than 6-digit resolution by efficiency-alone measurement of the reflected light; (2) We can achieve more than 8-digit resolution if we employ phase detection of the reflected light at the same time.Result of experimental inspection: (3) We confirmed (1) mentioned above by an experiment; (4) If we employ a PEM (photoelastic modulator) and use homodyne detection, the phase detection can achieve the resolving power of (2) because the instrumental resolution in phase detection can be 0.1 degrees.