Concentrating light into nanometer domain using nanoscale ridge apertures and its application in laser-based nanomanufacturing

In this work, we investigate light concentration in nanoscale ridge apertures and its applications in nanomanufacturing. Optical transmission of ridge apertures in a metal film is optimized by numerical design using the finite-difference time-domain (FDTD) method. We show that ridge apertures provide an optical transmission enhancement of several orders of magnitude higher than regularly shaped nanoscale apertures, and also confine the transmitted light to nanoscale dimensions. We fabricated these ridge apertures in metal film coated on quartz substrates by focused ion beam (FIB) milling. These apertures are characterized by nearfield scanning optical microscopy (NSOM). The ridge apertures are also used as a nanoscale light source for nanolithography. Holes with sub-100 nm dimensions are produced in the photoresist with visible and UV laser illuminations. The performance of the ridge apertures is compared with that of regular nanoscale apertures to demonstrate their advantages and promising potentials for many near-field optical applications.