Construction and Analysis of an Inexpensive Arduino-Based Rotating Quarter-Wave Plate Stokes Polarimeter*

Optical manipulation of self-assembled quantum dots relies heavily on the polarization of the light sources used to control them. In order to quickly measure the polarization at various points in the optical path, we have created an inexpensive polarimeter that is able to determine the polarization of incoming light by passing it through a rotating quarter-wave plate, a stationary polarizer, and measuring the light intensity with a photodiode. An Arduino microcontroller performs the analysis, conducting a Fourier transform on the intensity signal then analyzing the frequency components. Updating four times per second, an LCD displays the Stokes Vector to three significant figures, accurately providing a real-time measurement of the polarization. The electrical and mechanical components for the device cost less than $200, and no other elements – such as an oscilloscope – are necessary for the measurement.