Volumetric formation of structures

A system comprising:

• an illuminator configured to emit a beam of illumination with a peak wavelength in a bandwidth;
• a modulating device down an optical path from the illuminator for receiving the beam of illumination from the illuminator and configured to alter the beam of illumination into altered illumination;
• a layer of fabrication medium down the optical path from the modulating device, wherein the optical path extends through the layer of fabrication medium along an optical axis;
• and
• a controller configured to:
• use the illuminator to illuminate a portion of the layer of fabrication medium with the beam of illumination altered by the modulating device, wherein the fabrication medium is optically curable within the bandwidth to form a cured structure of the portion of the layer of fabrication medium that is illuminated by the altered illumination, wherein the beam of optical illumination is incident on the layer of fabrication medium along an optical axis, and
• use the modulating device to concentrate the beam of optical illumination in the layer of fabrication medium to form a volumetric structure in the layer of fabrication medium that is contoured relative to the illumination axis.