Laser speckle field as a multiple particle trap

We demonstrate that a speckle pattern in the spatially coherent laser field transmitted by a diffuser forms a multitude of three-dimensional intensity micro-pockets acting as particle traps for air-borne light absorbing particles. Confinement of up to a few thousand particles in air with a unidirectional single beam has been achieved. Theoretical analysis of the speckle defined trapping volume is in a good agreement with experimental results on capturing of aggregates of carbon nanoparticles in air.