Abstract: This application teaches various implementations of methods and in-line polarimeters with free-space sampling elements to sample four sample beams for determining the polarization state of input light. In one exemplary implementation, a device in this application includes four optical polarization analyzers arranged in series to form an optical path in free space to split four sample beams with four different states of polarization from an input optical beam propagating along the optical path. Each optical polarization analyzer transmits a majority of the input optical beam along the optical path and splits a fraction of the input beam as a respective sample beam. The device also includes four optical detectors respectively positioned in optical paths of the four sample beams to convert the sample beams into four detector signals indicative of optical power levels of the four different states of polarization, respectively.