Ultrafast laser nanostructuring for photonics and information technology

Abstract

The field of ultrafast laser nanostructuring is growing rapidly with the need to search for more advanced fabrication solutions, medium possessing the advantages of both flexibility and tunable optical properties which can be effectively exploited for the integration of polarization sensitive modifications into optical elements and multidimensional optical data storage.Any material that support nanogratings are of interest for being explored for multidimensional data storage. Therefore, the self-assembled nanostructures by femtosecond laser irradiation are explored in several different materials, such as alkali-free alumina-borosilicate glass, GeO2 glass, and indium-tin-oxide (ITO) thin film. The growth of the induced retardance associated with the nanograting formation in alumina-borosilicate glass is three orders of magnitude slower than in silica glass. The pulse energy for maximum retardance in GeO2 glass is ~65% lower than in fused silica. Direct-write femtosecond laser nanostructuring of ITO thin film is also demonstrated where the deep-subwavelength ripples with periodicity of down to 120 nm are realized originating the form birefringence (|Δn| ≈ 0.2), which is 2 orders of magnitude higher than the commonly observed in uniaxial crystals or femtosecond laser nanostructured fused quartz.The comparison of a femtosecond laser induced modification in silica matrices with three different degrees of porosity is given. The maximum retardance value achieved in porous glass is twofold higher than in fused silica, and tenfold greater than in aerogel. The polarization sensitive structuring in porous glass by two pulses of ultrafast laser irradiation is demonstrated, as well as no observable stress is generated at any conditions.Applying the acquired knowledge along with full control of laser system, the polarization sensitive elements are combined into multidimensional data storage providing the main processing conditions required for sufficient practical implementation of the technique. Finally, the proposed improvements in terms of high capacity and high density elevate the technology and potentially push the currently known boundaries to the higher level