High Stability Dual Beam Interferometer Sensor for Non-contact Photoacoustic Imaging

As a non-contact photoacoustic sensor, the reflector of one arm of dual beam interferometer sensor is usually composed of the upper surface of the ultrasonic coupling liquid coated on the surface of the sample. The vibration of the outside and the scanning motor cause the liquid level to shake, causing the reflected probe light path to deviate from the incident light path, which then reduces the detection stability of the sensor. In view of the above problems, a novel high stability dual beam interferometer sensor is introduced in this paper, in which the reflected probe light is derived from the original optical path by using the combination of PBS and quarter wave plate, and the reflected probe light is coupled into 50/50 beam splitting fibre by using aspheric mirror group. The influence of the radius and focal length of each aspheric mirror and the numerical aperture of the optical fibre on the detection stability of the sensor is theoretically analyzed. The results show that the structural design greatly reduces the effect of the vibration of the outside and the scanning motor on the detection stability of the sensor, and provides a theoretical basis for the development and performance optimization of the sensor.