Experiments on the data recording of optical waveguide multilayer storage devices

The basic principles of optical waveguide multilayer storage (WMS) device include recording data in the form of waveguide defects, reading data by collecting the scatter light from the waveguide defects, and restraining the cross talk between layers by taking the benefit of the waveguide structure. In this paper, we give some experimental results obtained by three different approaches of data recording. They are laser direct writing, photolithography and hot embossing. In the first method, a laser beam is focused on the top of a polymer film. The thermal effect alters the medium property locally at the focus point, which acts as the defect in the waveguide structure. The second method resorts to the processes of photolithography to record pits on the photoresist layer. The process of hot embossing is similar to the fabrication of CD-ROM, however, the data pits deeper than the wavelength are embossed on the polymer surface to increase the scattering efficiency. WMS devices based on different data writing methods are presented and the data scattering patterns are observed. The comparison between the different data writing approaches is made and discussed as well.