Search for new-physics through possible anomalous t\bar {t}\gamma , tbW and \gamma \gamma H couplings which are generated by SU(2)\times U(1) gauge invariant dimension-6 effective operators is discussed, using energy and angular distributions of final charged-lepton/b-quark in \gamma \gamma \to t\bar {t} \to \ell X/bX for various beam polarizations. Optimal beam polarizations that minimize uncertainty in determination of those non-standard couplings are found performing an optimal-observable analysis.

PACS numbers: 14.65.Fy, 14.65.Ha, 14.70.Bh