Hello Hexe,
To obtain a contour plot with the states of polarization, you can use the 'contour' function in MATLAB. This function will help you generate a contour plot with any number of contour levels, representing the states of polarization in the XY-plane. You can adjust the number of contour levels to achieve the desired level of detail in the plot.
You can refer to the documentation of the 'contour' function to know how to use it in your code: https://www.mathworks.com/help/matlab/ref/contour.html
Hope this helps!