Photopolarimetric investigations – Role of Pancharatnam retarder

An optical Polarimeter which uses Pancharatnam superachromatic half wave plate and quarter wave plate for modulation, was constructed at Physical Research Laboratory, Ahmedabad. This is a precision instrument capable of measuring polarization to an accuracy of 0.03%, in the flux limited case, in the whole of the optical region. The instrument works very efficiently on the telescope which is possible due to the use of superachromatic Pancharatnam retarders. Besides optical Polarimeter, an infrared (IR) Polarimeter, which also used superachromatic (1 to 2.5 micron) Pancharatnam retarders, has also been developed in PRL. The instrument has been tested in the laboratory and astronomical observations are planned in the near future. Several important results have already been obtained with optical photopolarimeter. Some of the results are briefly summarized in this article.