Two-Color Single-Photon Photoinitiation and Photoinhibition for Subdiffraction Photolithography

Subwavelength Patterning Microscopists have recently achieved fluorescence imaging at subwavelength resolution by focusing one beam of light in a halo around another beam, thereby quenching the glow of fluorescent dyes in all but the very center of the illuminated spot. Three studies have now adapted this approach to photolithography (see the Perspective by Perry ). Andrew et al. (p. 917 , published online 9 April) coated a photo-resist with molecules that, upon absorbing the ultraviolet etching beam, isomerized to a transparent layer but returned to the initially opaque form upon absorption of visible light. Applying an interference pattern with ultraviolet peaks superimposed on visible nodes restricted etching to narrow regions in the center of these nodes, yielding lines of subwavelength width. Scott et al. (p. 913 , published online 9 April) used a central beam to activate polymerization initiators, while using a halo-shaped surrounding beam to trigger inhibitors that would halt polymerization. Li et al. (p. 910 , published online 9 April) found that use of a different initiator molecule allowed both beams to share the same wavelength (800 nanometers), with a relatively weak quenching beam lagging a highly intense initiating beam slightly in time. Both the latter techniques produced three-dimensional features honed to subwavelength dimensions.