Fabrication of three-dimensional microscopic structure by VCSEL array trapping

We developed a new type of optical manipulation technique by using a VCSEL array, which we call VCSEL array trapping. Flexible manipulation of small objects is achieved by controlling the spatial and the temporal intensity distribution generated by the VCSEL array sources. We have previously demonstrated parallel translation and non-mechanical translation of microparticles by controlling the emission distribution of the VCSEL array as the light source. Furthermore, we found that a stacked structure when using 2x2 VCSEL beams can be fabricated. In this report, we clarify the stacking process and the conditions for stacking the maximum number microparticles in order to apply this stacking method to three-dimensional structure fabrication. As an experimental result, we confirmed that the stacked structure was lifted up from the sample stage and fabricated without the space between the microparticles. The stacked structure depended on the microparticle size, the beam waist position, and the spot pitch. Furthermore, we investigate the difference of stacking processes when using 2x2 beams and a single beam. As a result, we found that the structure can be fabricated with lower optical power than when using a single beam. This fact indicates that 2x2-beam illumination is particularly effective for stacking micro objects without damage caused by heat.