Waveguides and markings inside transparent materials by fs-laser radiation

Localized, three-dimensional refractive index changes are generated by focused femtosecond laser radiation (?= 1045 nm, ? 500 fs) in the volume of transparent materials. Depending on the scanning direction and laser parameters both waveguides and colorful markings are produced in a depth of d = 150-200 ?m below the surface of glass materials. The micro morphology of the irradiated structures is studied with light microscopy revealing a homogenous and crack-free modification. Depending on the angle of light incidence wavelengths of the visible light are diffracted at structured grids leading to bright colors in the observer's eyes. The optical guiding properties of the waveguides are investigated by far field measurements obtaining their numerical aperture. By using femtosecond double pulses instead of single pulses an increase in the numerical aperture of the fabricated waveguides is achieved. Results regarding the characteristics of double pulse waveguides in fused silica as well as examples for colorful marking in glass and crystals are presented.