Integrated optical pickup system for axial dual focus

We propose an optical pickup, which acquires data from both layers of a dual layer DVD simultaneously. An adaptive optical element using liquid crystals creates two axial foci separated by a spacing of 55µm, which is the distance between the two layers. The spacing between the foci can be varied by the adaptive element. The separation of the reflected light into TE and TM polarised light, corresponding to each of the layers, is done by dielectric gratings that are characterised by high aspect ratios. Electron-beam-lithography and reactive ion etching techniques were used to produce the sub-micrometer-structures. All fabricated elements were assembled in a pickup system, whose properties were measured.