Laser marking in transparent materials and mechanisms of laser-induced defect formation laser-induced marks as information carriers in digital encoding

Laser-based technological approaches and methods suitable for volumetric optical recording of digital information and creation of images by formation of different kinds of micromarks in the bulk of materials, transparent for a selected laser wavelength, are evaluated and discussed. Along with the analysis of formation of laser-induced parameterized centers with different geometries in glass, some emphasis is put on laser-induced creation of dark marks in organic materials, particularly in polystyrene containing light-absorbing inclusions. Parameterized marks with varying appearance or data pixels can serve as multi-bit information carriers. The dominant mechanisms of laser radiation absorption and induced formation of marks in different transparent materials are discussed.