Optical manipulation based on tightly focused high-order axially symmetric polarized beams

High order axially symmetric polarized beams (ASPBs) can create multiple focused spots under tight focusing conditions, and thus have been highly recommended for optical manipulation, but the feasible experiments have never been demonstrated. Cells trapping and manipulation based on optical tweezers using high order ASPBs are presented theoretically and experimentally to verify its feasibility and effectiveness. The focused intensities and corresponding gradient forces for high order ASPBs are first analyzed and calculated if two kinds of particles are trapped respectively based on the electromagnetic theory. Then an optical tweezers based on an inverted microscopy using high order ASPBs is built up, and the yeast cells (~10μm) are trapped and manipulated to shift and rotate using two kinds of ASPBs with P=1 and P=3. One yeast cell is stably trapped and shifted with a speed about 40μm/s and four yeast cells are trapped and rotated simultaneously with a rotation speed about 45°/s, which can also be further modulated and the track of the focusing spot can be programmed by computer. Finally, the optical trap stiffnesses are calculated theoretically using the Boltzmann statistics method and further measured experimentally when the filling factors of the objective lens are 0.50, 0.80 and 1.00 respectively and three microcopy objective lenses with numerical apertures 0.40, 0.65 and 0.85 are used, and the measured results agree well with the calculated results, which shows the trapping performances can be flexibly modulated by setting the system parameters and provides some novel choices for optical manipulations. All these findings benefit the expansion of the practical applications of vector beam OTs in some fields, especially in the field of biomedicine.