  We report a versatile and cost-effective way of controlling the unsaturated
loss, modulation depth and saturation fluence of graphene-based saturable
absorbers (GSAs), by changing the thickness of a spacer between SLG and a
high-reflection mirror. This allows us to modulate the electric field intensity
enhancement at the GSA from 0 up to 400%, due to the interference of incident
and reflected light at the mirror. The unsaturated loss of the
SLG-mirror-assembly can be reduced to$\sim$0. We use this to mode-lock a VECSEL
from 935 to 981nm. This approach can be applied to integrate SLG into various
optical components, such as output coupler mirrors, dispersive mirrors,
dielectric coatings on gain materials. Conversely, it can also be used to
increase absorption (up to 10%) in various graphene based photonics and
optoelectronics devices, such as photodetectors.
