Two for the price of one: generation of reconfigurable pairs of orthogonal polarization vortices using a Sagnac interferometer

We propose and demonstrate experimentally for the first time, to the best of our knowledge, a novel simple and stable scheme for generation of pairs of orthogonal polarization vortices/cylindrical vector beams based on a Sagnac interferometer. In particular, for an intracavity vortex of order 1 a pair of radially and azimuthally polarized beams is produced in the two ports of the interferometer, and more complex cylindrical vector beams are obtained for higher order vortices. Moreover, we show that three simple techniques can switch/reconfigure these outputs to another pair of orthogonal vector vortex beams, namely saddle or hybrid modes. The switching is achieved by rotating either the intracavity quarter-wave plate or the input polarization by 90° or by introducing a half-wave plate into the Sagnac loop at 45° to the interferometer plane. Our scheme can find applications in optical information transmission/mode division multiplexing, information encoding, laser micromachining, and optical manipulation/particle trapping.