We develop a miniaturized optical signal pickup module, with a working wavelength of 650 nm, and an image numerical aperture (NA) of 0.6, comprised of several SiNX optical phase elements on stacked Si substrates, for use in optical storage systems. The optical module, which is optical-on-axis and transmissible in both visible and infrared ranges, is designed to include not only a light source, but also diffractive optical elements (DOEs), which can be made with micro-optoelectromechanical systems (MOEMS) technology. Its optical operation is simulated by ray tracing to optimize the spot size (∼0.6 μm) focused on the disk by adjusting the tolerance of each element in the alignment. All the Si-based transmission optical elements are fabricated and stacked by self-alignment bonding to reduce the tolerance of the assembled system. We obtain a circular focused spot when the full-width at half maximum (FWHM) of the zero-order beam is 3.1 μm; the diffraction limited spot size on the optical disk is 0.7 μm.
- Diffractive optical elements
- Pickup module