Immunosensor based on optical heterodyne phase detection

An immunosensor based on optical heterodyne phase detection was developed. A transverse Zeeman laser was employed as the light source in this sensor, which includes a p-polarized light and an s-polarized light, as the light source. For phase detection, the measurement accuracy is improved by replacing dc detection of luminous intensity with ac detection to avoid the impact of shift in the case of dc detection. Theoretical analysis indicates that phase change relies strongly on the thickness of the sensing membrane and the material and thickness of the metallic membrane. An experimental apparatus was constructed with optimized design parameters, and a research was conducted on the dynamics of interaction between ricin and its antibody. Experimental results show that the sensor has good performance in sensitivity, stability and reliability.