Fig. 1. Schematic diagram of super-resolution refractive index measurement principle using parity detection

Fig. 2. (a) Sensitivity curve of intensity-detection-based refractive index measurement and (b) signal optimal sensitivity as a function of photon number and transmittance

Fig. 3. Signals of parity detection and normalized intensity detection are plotted as a function of refractive index n for the average photon number of . The red dotted line and black solid line represent parity detection (PD) and normalized intensity detection (ID) respectively 奇偶探测信号和归一化强度探测信号随折射率n的变化，输入信号的平均光子数 ，红色点线和黑色实线分别代表奇偶探测信号和归一化强度探测信号

Fig. 4. FWHMs of parity and intensity detections varying with the average photon number (a) and transmittance (b)

Fig. 5. Sensitivity curves of parity detection (red dotted line) and intensity detection (blue solid line), and the black dashed line represents their common tangents

Fig. 6. Optimal sensitivity of parity detection and intensity detection signals varying with transmittance (a) and photon number (b). The red dot dashed line indicates parity detection and the blue solid line represents intensity detection