Subwavelength-resolvable focused non-Gaussian beam shaped with a binary diffractive optical element

The diffraction-limited spot size limits the optical disk storage capacity and microscopic resolution. We describe a technique to shape a focused Gaus sian beam into a superresolving beam by using a diffractive optical element fabricated by laser-assisted chemical etching. The focused shaped beam has a smaller width and a longer depth of focus than a similarly focused Gauss ian beam. Using the diffraction-limited shaped beam along with threshold wr iting, we achieved a written pit size of less than 0.33 mu m at a 695-nm la ser wavelength, compared with a 0.7-mu m focused Gaussian spot size (full w idth at e(-2) of the peak) with the same focusing lens. The energy conversi on efficiency for the beam shaping was similar to 81%. (C) 1999 Optical Soc iety of America.