Investigation of diffractive grating creation in glass by using femtosecond laser pulses

In this paper, the interaction of femtosecond laser pulses with BK7 glass is investigated. A Ti:sapphire femtosecond laser with the chirped pulse amplification is used. By studying the diameter of the ablated area, the threshold fluence for the 40 femtosecond pulses at the 800 nanometers is obtained to be around 2.7 J/cm2</sup>. By moving the position of the laser focus into depth of the glass, and by changing the translation speed of the femtosecond laser pulses, depth of the glass has been micro machined by laser pulses. By using CCD camera pictures, obtained from propagation of the He-Ne light through the micromachined region, effect of the interaction with three different translation speeds, 0.01, 0.02 and, 0.05 mm/s is investigated. The results show that the diffractive grating is formed inside the volume of the glass due to the interaction of 10 femtosecond laser pulses having 0.35 microjoules at each position. Finally, the created diffraction grid step is obtained about 4.52 micrometers.