Surface topographic characterization of optical storage devices by Digital Holographic Microscopy

In this study, we have used Digital Holographic Microscopy (DHM) for surface topographic characterization of the optical storage devices. Optical storage devices like Compact Discs (CDs) and Digital Versatile discs (DVDs) are used worldwide for memory storage, grating, sensing and spectroscopy applications. These devices can store the information in binary form on a spiral track in the data recording layer. We demonstrate that these data tracks can be characterized through DHM and one can decode the binary data in transmission mode. The experimental results are shown for blank (without data) and burned (with data) areas of CDs and DVDs. The average width of the CD and DVD data track is experimentally found to be 600 ± 30 nm & 230 ± 20 nm, respectively and the thickness of the data recording track is obtained as 80 ± 10 nm. The obtained results are verified by Field Emission Scanning Electron Microscopy (FESEM) measurements and found a very close agreement between the two results. In addition, the proposed method can also be used for manufacturing defect identification and measurement.