Near-Field Multiphoton Nanolithography Using an Apertureless Optical Probe

Near-field multiphoton optical lithography is demonstrated by using ~120 fs laser pulses at 790 nm in an apertureless near-field optical microscope, which produce the lithographic features with ~ 70 nm resolution. The technique takes advantage of the field enhancement at the extremity of a metallic probe to induce nanoscale multiphoton absorption and polymerization in a commercial photoresist, SU-8. Even without optimization of the resist or laser pulses, the spatial resolution of this technique is as high as λ/10, nearly a factor of two smaller than the previous multiphoton lithography in the far field.