Provided is an optical device with improved phase shift and propagation loss of light without decreasing the dynamic characteristics of the optical device. Specifically, techniques are provided for coordinating the write-to-disk operations performed on such data items to ensure that older versions of the data item are not written over newer versions, and to reduce the amount of processing required to recover after a failure. The full digital images generated with the first number of picture elements are divided into two part digital images, each having a number of picture elements used for storing image information. A bookmark corresponds to a multimedia content. An apparatus and methods of the making the thermal management material are also described, which includes a roll-to-roll apparatus for making the thermal management material. The second schedule is based on the second relationship strength and the second relationship strength is different from the first relationship strength.