Reduction of Optical Feedback Effects during Reading and Writing in Optical Recording
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-02
A special optical head assures substantial reduction of optical feedback during both reading and writing. The basic concept is to place an optical delay line of appropriate length between the laser and the disk so that the laser is turned off when the back reflected light impinges on the laser front facet. For writing a suitable effective delay path length L (including dispersion effects of the optical components in the head) is chosen so that 2L/c>Wtw, where Wtw is the duration of the writing pulse. The carrier concentration in the laser waveguide channel decays in no more than 3 ns either by spontaneous emission or by carrier diffusion in lasers with no lateral carrier confinement. By choosing 2L slightly larger than c x Wtw the back reflected laser light will experience no gain.