Fast, High-Precision Optical Polarization Synthesizer for Ultracold-Atom Experiments

We propose a novel approach to precisely synthesize arbitrary polarization states of light with a high modulation bandwidth. Our approach consists in superposing two laser light fields with the same wavelength, but with opposite circular polarizations, where the phase and amplitude of each light field are individually controlled. To assess the precision of the synthesized polarization states, we characterize static spatial variations of the polarization over the wavefront, as well as the noise spectral density of temporal fluctuations. We find that static polarization distortions limit the extinction ratio to $2\times 10^{-5}$, corresponding to a 0.01% reduction of the degree of polarization (DOP). We also obtain that temporal fluctuations give rise to a $0.2^\circ$ uncertainty in the state of polarization (SOP). We recently demonstrated an application of the polarization synthesizer (Robens et al., arXiv:1608.02410) to create two fully independent, controllable optical lattices, which trap atoms depending on their internal spin state. Probing ultracold atoms in polarization-synthesized optical lattices, we obtain an independent, complementary characterization of the optical performance of the polarization synthesizer.