High-sensitivity Stokes spectropolarimetry on cyanobacteria

We investigate the spectral signatures arising from the optical properties of chlorophyll in linear and circularly polarised scattered light from cyanobacteria. We include Stokes scattering coefficient measurements on two cyanobacteria species, Chroococcidiopsis and Synechococcus to a fractional polarisation of ±0.0001 across visible wavelengths. We find that the largest circularly polarised optical signatures from our cyanobacteria samples can be described by optical scattering from spheroidal objects with internal reflections and absorption and, importantly, light scattering from chiral processes is not identifiable in our narrow band light scattering data. We believe previous light scattering measurements attributing chirality effects to cyanobacteria may have been dominated by internal scattering processes.