  Differential cross sections at $t=t_{\text{min}}$ and decay asymmetries for
the $\gamma p\rightarrow\phi p$ reaction have been measured using linearly
polarized photons in the range 1.5 to 2.9 GeV. These cross sections were used
to determine the Pomeron strength factor. The cross sections and decay
asymmetries are consistently described by the $t$-channel Pomeron and
pseudoscalar exchange model in the $E_{\gamma}$ region above 2.37 GeV. In the
lower energy region, an excess over the model prediction is observed in the
energy dependence of the differential cross sections at $t=t_{\text{min}}$.
This observation suggests that additional processes or interference effects
between Pomeron exchange and other processes appear near the threshold region.
