  Ultracold molecular gases are promising as an avenue to rich many-body
physics, quantum chemistry, quantum information, and precision measurements.
This richness, which flows from the complex internal structure of molecules,
makes the creation of ultracold molecular gases using traditional methods
(laser plus evaporative cooling) a challenge, in particular due to the
spontaneous decay of molecules into dark states. We propose a way to circumvent
this key bottleneck using an all-optical method for decelerating molecules
using stimulated absorption and emission with a single ultrafast laser. We
further describe single-photon cooling of the decelerating molecules that
exploits their high dark state pumping rates, turning the principal obstacle to
molecular laser cooling into an advantage. Cooling and deceleration may be
applied simultaneously and continuously to load molecules into a trap. We
discuss implementation details including multi-level numerical simulations of
strontium monohydride (SrH). These techniques are applicable to a large number
of molecular species and atoms with the only requirement being an electric
dipole transition that can be accessed with an ultrafast laser.
