  We investigate one- and two-photon absorption in twisted bilayer graphene
(TBLG) by examining the effects of tuning the twist angle $ \theta $ and the
excitation energy $ E_l $ on their corresponding absorption coefficients $
\alpha_{i=1,2}$. We find that $ \alpha_1 $ shows distinct peaks as a function
of $ E_l $ which correspond to the van Hove singularities (vHS) of TBLG. In
contrast to single- (SLG) and AB bilayer graphene (BLG), $ \alpha_1 $ is
substantially enhanced by $\sim 2$ and $\sim 1$ orders of magnitude,
respectively, in the visible range. On the other hand, $\alpha_2 $ exhibits a
remarkable increase of $\sim 11$ and $\sim 9$ orders of magnitude.
Interestingly, as $\theta$ increases, the resonant features exhibited by
$\alpha_{i=1,2}$ \textit{vs.} $ E_l $ shift progressively from the infrared to
the visible. On doping TBLG, both $\alpha_1 $ and $ \alpha_2 $ remain
essentially unchanged \textit{vs.} $ E_l $ but with a minor red-shift in their
resonant peaks. Additionally, we explore various polarization configurations
for TPA and determine the conditions under which $\alpha_2$ becomes extremal.
