Experimental realization of a resource-saving polarization-independent orbital-angular-momentum-preserving tunable beam splitter.

The tunable beam splitter (TBS) is a fundamental component used in optical experiments. A TBS can preserve the orbital angular momentum (OAM) states; in addition, the polarization states of photons are valuable for some particular experiments, such as high-dimensional quantum information processing. We use polarization beam splitters and half-wave plates to realize such a TBS under a compact structure, which can reduce the number of elements that require comparing with existing works. The experiments verify that the TBS has good performances in tunability, polarization, and OAM state preservation. A Sagnac interferometer is implemented with the proposed TBS to evaluate its practical usability, and the mean visibilities greater than 99.30% under varying polarization states demonstrate its potential for optical information processing.