# Creating certain polarisations from light source

Two plane polarized beams of light of equal intensity with polarizations that are mutually orthogonal are produced from a gas discharge lamp emitting nearly monochromatically at mean wavenumber ν and with bandwidth ∆ν using a polarizing beamsplitter.

I would like to create: 1) A circularly polarised beam 2) An unpolarised beam

I'm wondering are those 2 orthogonally polarised beam from the gas discharge lamp completely uncorrelated? In other words, just by combining them will give me "2) An unpolarised beam"?

and.. I got no idea how to create a circularly polarised beam. Any suggestions?

For two polarized sources superimposing, the resultant beam has several parameters (relative: amplitudes, phase shifts, frequencies, and polarization angles.) Your desired setup fixes all but the latter, and changing that will only ever output another plane polarized beam. To get say a circular beam, you need a $\pi/2$ phase shift between the two. Here's an animated graph to illustrate the general case. All you to need to play with are the relative parameters. There are three plots: source 1, 2, and superimposed, as well as a particle trajectory for each.