Polarisation sensor for determining light source eg laser beam - cyclically modulates polarisation of input beam using rotating half-wave plate or Faraday cell and analyses using beam divider and differential amplifier to distinguish signal from background.

摘要

The sensor receives an optical beam and cyclically modulates its polarisation state. The resulting signal is analysed to detect the difference between a polarisation signal of interest and randomly polarised background signals. The modulation device rotates the polarisation plane of the incident radiation. It can consist of a rotatable half-wave plate (14) with a rotary drive (16). Alternatively, it can contain a Faraday cell subjected to a variable magnetic field. USE - Sensor is used to determine polarisation characteristics of light source.