Diffractive optics enable applications requiring high power laser focusing and beam shaping. The ability of such components to resist damage is of mounting importance as lasers attain higher power levels. Diffractive optics inherently contain discontinuities that can enhance electric field distributions within the component. Researchers have previously analyzed subwavelength, anti-reflective gratings for geometrical field enhancement effects, but conventional diffractive elements have not received as much attention. In this paper, we apply rigorous electromagnetic simulations to multi-level diffractive optics to explore potential connections between basic grating parameters (period, depth, number of levels), geometrical field enhancement, and laser damage.