Cylindrical vector beam sorter with spin-dependent spiral transformation

Abstract

Here, we propose and experimentally demonstrate a cylindrical vector beam (CVB) sorter based on a spin-dependent spiral transformation. By exploiting the spin–orbital interaction of the geometric phase, a pair of conjugated spiral transformations are applied to modulate the two orthogonal circularly polarized components of the CVB, which are converted into the same linear phase gradient from opposite azimuthal phase gradients. Since the orthogonal spin components of CVBs with different polarization orders carry different phase gradients, under the convergence of a convex lens, the coaxially transmitted CVBs can be sorted with spatially separated positions, and the increased phase gradient provided by the spiral transformation yields the high resolution. We show that five CVB modes from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>−</mml:mo> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>2</mml:mn> </mml:mrow> </mml:math> to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>+</mml:mo> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>2</mml:mn> </mml:mrow> </mml:math> are successfully sorted with a separation efficiency of 3.65. As a proof-of-concept, we demonstrate a two-channel CVB multiplexing communication with a bit error rate approaching <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msup> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>−</mml:mo> <mml:mn>6</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> . In addition to providing an avenue for CVB demultiplexing, our results show potential applications in mode filtering and mode routing in all-optical interconnection.