  We study in two space-time dimensions (d = 2) the relation between N = 2
supersymmetric (SUSY) QED theory and N = 2 nonlinear (NL) SUSY model by
linearizing N = 2 NLSUSY generally based upon the fundamental notions of the
basic theory. We find a remarkable mechanism which determines theoretically the
magnitude of the bare gauge coupling constant from the general structure of
auxiliary fields. We show explicitly in d = 2 that the NL/linear SUSY relation
(i.e. a SUSY compositeness condition for all particles) determines the
magnitude of the bare electromagnetic coupling constant (i.e. the fine
structure constant) of N = 2 SUSY QED.
