Strength control in multiple optical traps generated by means of diffractive optical elements

We present a simple technique to generate arrays of optical traps with different trapping forces. The arrays can be configured in two or three dimensions (2D, 3D) by means of phase diffractive optical elements (DOEs) displayed on a phase programmable modulator. DOEs design is based on the approach of spherical wave propagation and superposition, which enables to individually control the strength of the optical trap. Experimental results using silica beads trapped with different forces in 2D and 3D configurations are presented.