  We investigate photoproduction of $\omega$ off a nucleon target $\gamma
N\to\omega N$ by using a Reggeized model where
$\pi(135)+\sigma(500)+f_1(1285)+f_2(1270)$+Pomeron exchanges are included in
the $t$-channel for the reaction at forward angles. The reaction mechanism at
low energy is featured by the dominance of the $\pi$ exchange with the
absorptive cuts introduced to modulate the pion contribution to both $\gamma
p\to \omega p$ and $\gamma n\to \omega n$ reactions. Necessity of $\sigma$
exchange is illustrated in the analysis of the cross section from natural
parity exchanges. Cross sections for differential, total, and spin density
matrix with beam polarization are reproduced and compared with existing data on
$\gamma p\to \omega p$. Scaled differential cross sections of Jefferson Lab
data on $\gamma p\to \omega p$ are investigated at the production angle
$\theta=90^\circ$ with the nonlinear trajectories for a saturation.
Differential and total cross sections for the $\gamma n\to\omega n$ reaction
are analyzed to compare with recent experimental data at the CBELSA/TAPS
Collaboration. An application to the $\gamma p\to\omega\Delta^+$ reaction is
presented to demonstrate the significance of the $\pi$ exchange in the total
and differential cross sections.
