Generation of cylindrical vector beams and optical vortex by two acoustically induced fiber gratings with orthogonal vibration directions

Mode coupling from the fundamental vector mode (HE₁₁ ^x) to the cylindrical vector beams (CVBs) and optical vortex beams (OVBs) of a few-mode fiber excited by two acoustic flexural waves with orthogonal perturbations is achieved by using a composite acoustic transducer. The HE₁₁ ^x mode is converted to TM₀₁ and TE₀₁ modes, which have radial and azimuthal polarizations, by using the lowest-order acoustic flexural modes of F₁₁ ^x and F₁₁ ^y, respectively. Furthermore, HE₁₁ ^x mode can also be converted to the ± 1-order OVBs of HE₂₁ ^even ± iHE₂₁ ^odd through the combined acoustic modes of F₁₁ ^x ± iF₁₁ ^y. This technique provides a useful way of generating CVBs and OVBs in optical fiber with conveniently electrically-controlled mode conversion characteristics.