Realisation of active pulling/pushing laser beams for light-absorbing particles in the air with a pair of diffractive optical elements

Abstract

An approach for the realisation of active pulling/pushing laser beams for light-absorbing particles in the air is proposed and investigated. The approach is based on the use of a pair of cascaded diffractive optical elements generating first-order Bessel beams. The generated superimposed Bessel beams allow one to create self-imaging light fields in the form of optical bottle beam traps. In this case, the rotation of one of the cascaded elements causes the appearance of an additional phase difference between the superimposed beams, resulting in axial shifting of the generated self-imaging light patterns. During their movement, the trapped particles remain confined inside the dark regions of the generated light field. This approach allows one to easily realise so-called “optical conveyors”, which are crucial in the transportation and investigation of dangerous substances, viruses, living cells, or containers holding these substances. We believe that such optical conveyors based on photophoretic forces will find applications in future microdevices.