Functional Birefringent Elements Imprinted by Femtosecond Laser Nanostructuring of Multi-Component Glass

A decade ago, a new type of self-organization process was observed in the bulk of SiO2 glass after irradiation with ultrashort laser pulses [1]. Under certain irradiation conditions, highly ordered nanostructures with features smaller than 20 nm could be formed in the irradiated volume. The sub-wavelength arrangement of these structures results in form birefringence, which was recently exploited for demonstrating a variety of functional optical elements in silica glass [2]. Despite excellent physical and chemical properties of fused silica, the applications of this glass are limited due to the expensive manufacturing process associated with high melting temperature. Recently the evidence of laser-induced nanogratings in glasses other than SiO2 was reported, including GeO2 glass [3], binary titanium silicate glass (ULE, Corning) and multicomponent borosilicate glass (Borofloat 33, Schott) [4]. However, birefringence induced in borosilicate glass was more than one order of magnitude lower than in pure SiO2 glass.