A polarization-modulated multichannel Mueller-matrix scatterometer for smoke particle characterization

摘要

The polarization properties of scattered light are being exploited to determine the optical and physical information of small particles. In this paper, a scatterometer is developed for simultaneously measuring the Mueller scattering matrix elements as functions of the scattering angle. The scatterometer uses an electro-optic modulator to modulate the polarization state of the incident light, and uses two photomultipliers provided with different polarization optics to consist multichannel polarization-state detector. The instrument takes advantage of combination of the polarization-modulation technique and division-of -amplitude photopolarimeter, which make for a compact design and substantial increase in measurement throughput and speed. The methods of calibration and alignment using the polarization-modulated light are established, with which the instrument is calibrated precisely. The methods of data processing and error analysis of the measured Mueller matrix elements are developed. A hybrid experimental/theoretical approach to study the light scattering properties of smoke particles is also presented.