Capabilities of Laser-Induced Marks as Information Carriers Created in Different Materials

Laser technological approaches and techniques suitable for volumetric optical recording of digital data and image formation by creation of micromarks (data bits, pixels, and other information carriers) in the bulk of different materials are analyzed. Laser-induced marking centers with different controlled geometric parameters (size, shape, orientation, etc.) are obtained by varying the focal area, wavelength, duration and energy of laser pulses, temperature of objects and also applying external or local internal stresses in irradiated samples. The laser-based methods for creation of colored and dark marks in transparent glasses and polymers with special light-absorbing inclusions are studied. Black marks are created in plastics because of formation of carbonaceous products as a result of pyrolysis of the polymer matrix due to absorption of focused laser radiation by optical inhomogeneities. Embedding absorptive microparticles into the volume of transparent polymers makes the marking procedure more effective and predicted and it increases contrast and resolution of the marking area inside the plastics. The laser-based techniques of formation of light-emitting centers in specialized fluorescent materials and their applicability for data recording are discussed. Emitting marks are obtained in thermally stable photosensitive organic chromone-based materials by two-photon interaction process under irradiation with a focused laser beam.