Nanophotonic light management concepts are essential building blocks of advanced thin-film solar cells. These concepts make use of light coupling to waveguide modes that are supported by the photoactive absorber material of the solar cell. In a recent study, we presented a new method based on scanning near-field optical microscopy that enables the direct nanoscale investigation of light coupling to an individual waveguide mode in a nanophotonic thin-film silicon solar cell. Making use of this method, we investigate in this contribution the polarization dependence of the light coupling to a waveguide mode. Based on this polarization dependence, we can attribute the investigated waveguide mode to a transverse electric mode. Moreover, we identify the grating vector, which is responsible for the light coupling to the investigated waveguide mode in the nanopatterned thin-film silicon solar cell.