  We report optical spectroscopy and ultrafast pump-probe measurements on the
antiferromagnetic heavy fermion compound CePt$_2$In$_7$, a member showing
stronger two dimensionality than other compounds in CeIn$_3$-derived
heavy-fermion family. We identify clear and typical hybridization spectral
structures at low temperature from the two different spectroscopy probes.
However, the strength and related energy scale of the hybridization are much
weaker and smaller than that in the superconducting compounds CeCoIn$_5$ and
CeIrIn$_5$. The features are more similar to observations on the
antiferromagnetic compounds CeIn$_3$ and CeRhIn$_5$ in the same family. The
results clearly indicate that the Kondo interaction and hybridizations exist in
the antiferromagnetic compounds but with weaker strength.
