Nonlinear interaction between optical vortex and cyanobacteria fragments in solution

Optical forces generated by interaction between light and biomaterials induce an optical waveguide, leading to a deep penetration of light in a scattering suspension. In contrast, we report on the optical vortex induced exotic nonlinear phenomena not only the conventional self-trapping effects. A 532 nm continuous-wave right-/left-handed first-order optical vortex was focused to be an annular spot with a diameter of 40 um in cyanobacteria suspensions, where their nonlinearity was controlled by appropriately mixing seawater and glycerol. The incident optical vortex underwent strong self-defocusing effects in the suspensions with a high mixing ratio of glycerol, resulting in the creation of the dark soliton. The spatial symmetry breaking of the incident optical vortex further occurred in the moderate mixing ratio, manifesting the modal instability effects. Furthermore, the broken optical vortex then rotated towards a clockwise/anticlockwise direction assigned by its handedness.