Power and Focusing Considerations for Recording with a Laser Beam in the TEM(00) Mode

Some of the aspects of recording and reading with a focused laser beam in the TEM(00) mode are analyzed. The effects of defocusing and laser power variations on the recorded spot size are presented for various peak-to-threshold intensity ratios. It is shown that by suitably choosing the f/number of the optical system minimum recording power is required. The distinction between optical writing and reading depth of focus is made. It is concluded that the effective depth of focus can greatly exceed the optical depth of focus, thus relaxing mechanical stability requirements in a practical laser recording system.