Miniature planar solid immersion mirror with focused spot less than a quarter wavelength

We describe a microoptical planar waveguide solid immersion mirror with high optical throughput, and show that it can focus light to spot sizes of ~90 nm at a wavelength of 413 nm. Scanning near field optical microscope images of the light within the device are in good agreement with a simple theoretical model. This device is accurately mass-produced with lithographic and thin film deposition techniques known from modern integrated circuit processing.