Optical resolution below λ/4 using synthetic aperture microscopy and evanescent-wave illumination

Evanescent-wave illumination is applied to synthetic-aperture microscopy on a transparent solid substrate to extend the resolution limit to lambda/2(n+1) (where n is the substrate refractive index) independent of the lens NA. Using a 633 nm source and a 0.4 NA lens, a resolution to 150 nm (lambda/4.2) is demonstrated on a glass (n = 1.5) substrate. Further extension to similar to 74-nm resolution (lambda/8.6) is projected with a higher index substrate (n = 3.3). (C) 2008 Optical Society of America