Self-energy of one electron in non-relativistic QED

We investigate the self-energy of one electron coupled to a quantized radiation field by extending the ideas developed recently by C. Hainzl. We fix an arbitrary cut-off parameter Lambda and recover the alpha^2-term of the self-energy, where alpha is the coupling parameter representing the fine structure constant. Thereby we develop a method which allows to expand the self-energy up to any power of alpha. This implies that perturbation theory is correct if Lambda is fix. As an immediate consequence we obtain enhanced binding for electrons.