| In order to fully analyze the polarization data taken last Thursday, I needed to convert the signal output (which is in volts) to power (units of watts). I used the power meter to accomplish this. Keeping the exact same configuration of PD's and beam splitting, opened the red pitaya's oscilloscope package. I then took the power meter, and held it in front of the PD to measure the amount of Watts at each PD. I then wrote down the corresponding voltage being seen in the red pitaya. I took 5 sets of measurements for each PD to get experimental accuracy. I then used a simple y = mx + b fit to find out the constant m that converts the input wattage into voltage. For the s polarization, the conversion factor is 0.83. For the p polarization, the conversion factor is 1.12. I then used this data to plot polarization angle as a function of time, and the relative intensity drift as a function of time. The plots are shown below. The physical meaning of the polarization angle is shown in the unit circle diagram below, in which P is the total power. |