The invention concerns a polarization rotator, comprising a first waveguide layer containing at least a first waveguide, said first waveguide having an input end and an output end, a second waveguide layer having at least a second waveguide, said second waveguide having an input end and an output end, and at least a first vertical mirror element arranged at the end of at least one of said waveguides to couple light between the output end of the first waveguide and the input end of the second waveguide. The optical axis of said first or second waveguide which has the vertical mirror element at its end is rotated in its waveguide layer at a first angle in order to induce rotation of polarization of light coupled between said first and second waveguides with an amount that corresponds to said first angle.