Diffractive solid immersion lenses characterization and manufacturing

Solid Immersion Lenses (SILs) have an outstanding potential for applications in future generations of optical data storage systems. We report the realization of a diffractive Solid Immersion Lens (dSIL) which is the diffractive analog of the refractive hemispherical SIL. Here, inside the medium the propagation angles of the first order diffracted waves point in the same direction as the incident angles from outside the SIL. We realized two types of dSILs: binary phase elements were fabricated in a highly refracting glass (LaSF35) by direct e-beam writing and successive reactive ion etching and dSILs with a blazed profile were manufactured in photoresist by holographic lithography. The minimum distance between adjacent zones in the diffracting structure is in the range of one wavelength. Polarization dependencies and phase impacts have to be considered in the design of an optical element with features this small. In comparison to the lithographically realized binary phas e grating, the holographic elements have the advantage of high diffraction efficiency.