Efficient volume Bragg gratings in various transparent materials induced by femtosecond laser pulses

Typically, volume Bragg gratings (VBGs) are fabricated in photo-thermo-refractive glass by exposure to an interference pattern of an UV laser. Due to the restriction to this special glass the method is very limited in its application with respect to monolithic integration of VBGs. In this paper the authors show that this can be overcome by making use of femtosecond laser pulses for the inscription of VBGs in nonphotosensitive glass. Due to the high intensity of focused femtosecond pulses, a refractive index change can be obtained even in nonphotosensitve glass through the process of nonlinear absorption. This process is additionally the cause for higher reflection orders one can see although a single period grating was inscribed and opens the door for using one grating at different wavelengths without the need to turn the grating for wavelength adaption.