Experimental generation of Laguerre-Gaussian beam using angular diffraction of binary phase plate

A phase plate was fabricated on a quartz crystal using ion beam etching technique with a predesigned angular phase mask, which can modulate the phase of light illuminating the phase plate by 0 and pi rind Analyzed the field distribution of the diffracted light by angular diffraction theory, which shows the resulting beam is a superposition of two Laguerre-Gaussian (LG) beams with opposite topological charges Illuminating the phase plate using the expanded beam with diameter 4 mm generates the superposition of two LG beams with the same radian index p = 0 and opposite angular index l =20 and l = -20. By increasing the aperture of the illuminating beam, LG beam with higher p index can be acquired, while the l index remains opposite.