Phys. Rev. Lett. 119, 058101 (2017)

Much recent study has focused on the propagation of light through complex scattering media, in part due to applications in biosensing. Now, Anna Bezryadina and colleagues have investigated the nonlinear transmission of light through biological suspensions of Synechococcus cyanobacteria. The team showed nonlinear self-trapping of a light beam propagating through seawater containing the bacteria. The team sent a beam of collimated green light (full-width at half-maximum size of 50 μm) into water samples with and without bacteria. After propagating a distance of 4 cm through water without bacteria, the beam had diverged to 650 μm, with no dependence on incident power. When 1.3 × 107 cells ml–1 were added to the water, the beam expanded to 1.25 mm due to scattering in the case of low incident optical powers (0.1 W), but for a higher power of 3 W the team observed self-trapping and a similar output beam size compared to the input beam size. The researchers hope that the results may lead to new approaches to tackle the problem of scattering losses in biophotonics, but further studies are required.