  We investigate a possibility if a loop diagram via Higgsino can enhance the
Higgs to diphoton decay width in supersymmetric models with an extension of
Higgs sector. A model with an additional non-renormalizable term of Higgs
fields is firstly analyzed where the higher order term can introduce the Higgs
coupling to Higgsinos as well as charged Higgs bosons. We point out that a
choice of the Higgs coupling to obtain a significant size of enhancement of
diphoton decay width reduces the Higgs mass and/or a size of non-renormalizable
term needs to be large and a cutoff scale is around the weak scale. Another
model in which the Higgsino mass term is generated by a non-perturbative
instanton effect via a strong dynamics in a context of SUSY QCD is also
suggested. It is shown that the sign of the Higgs coupling to fermions is
opposite from perturbative models due to an operator including bosonic fields
in the denominator and a constructive contribution to the diphoton decay
amplitude can be easily obtained in this kind of model.
