  We use a phase-only spatial light modulator to generate light distributions
in which the intensity decays as a power law from a central maximum, with order
ranging from 2 (parabolic) to 0.5. We suggest that a sequence of these can be
used as a time-dependent optical dipole trap for all-optical production of
Bose-Einstein condensates in two stages: efficient evaporative cooling in a
trap with adjustable strength and depth, followed by an adiabatic
transformation of the trap order to cross the BEC transition in a reversible
way. Realistic experimental parameters are used to verify the capability of
this approach in producing larger Bose-Einstein condensates than by evaporative
cooling alone.
