In exemplary implementations of this invention, hydrothermal synthesis of zinc oxide nanowires is morphologically controlled. In order to determining the transmission rate that is to be used at any given time, in such a way as to make the two match so as to minimize wasted bandwidth, the data stream is split into chunks chosen such that the average bit rate for the chunk as a whole is no less that the average bit rate for any shorter chunk starting at the same point. The data line and the scan line are formed in one layer. The workpiece is then implanted during a second pass at a second speed. The optical film according to the present invention has excellent heat resistance, optical transparency, etc.