In a Comment on a previously published article in this Journal [Phys. Rev. Applied 5, 024005 (2016)] 1 , Apertet states that the definition of the thermopower given in that article seems erroneous due to a confusion between the different physical quantities needed to derive this parameter. We believe some definitions need to be clarified in order to avoid confusions. We here intend to answer the questions of Apertet by detailing the method and by focusing on the definition of the quantities we optically measured.