A dark hollow beam from a selectively liquid-filled photonic crystal fibre

This paper reports that, based on the electromagneticscattering theory of the multipole method, a high-quality hollow beam isproduced through a selectively liquid-filled photonic crystal fibre.Instead of a doughnut shape, a typical hollow beam is produced byother methods; the mode-field images of the hollow-beam photoniccrystal fibre satisfy sixth-order rotation symmetry, according tothe symmetry of the photonic crystal fibre (PCF) structure. A darkspot size of the liquid-filled photonic crystal fibre-generatedhollow beam can be tuned by inserting liquid into the cladding regionand varying the photonic crystal fibre structure parameters. Theliquid-filled PCF makes a convenient and flexible tool for theguiding and trapping of atoms and the creation of all-fibre opticaltweezers.