Three-dimensional recording and structuring of chalcogenide glasses by femtosecond pulses

We report on three-dimensional (3D) holographic recording in As ₂S₃ glass using 800 nm wavelength, 150 fs duration pulses. Diffractive beam splitter was used to generate 2-5 beams which were then focused for recording by objective lens of numerical aperture NA = 0.75. The recorded 3D hologram was read out by diffraction of 632 nm HeNe laser beam confirming the expected pattern of holograms. The mechanism of photo-darkening and optical damaging of As₂S₃ glass and dielectrics in general is discussed. Two-photon absorption cross-section, σ₂ = 74.6 × 10^-50 cm⁴/s, was determined by transmission for pulses of 150 fs and 800 nm wavelength. Also, it is demonstrated that the optical damage threshold scales as the bandgap energy for the fluorides. Nano-/ micro-structuring of As₂S₃ glass by ablation in air will be also demonstrated. High fluence (> 5 J/cm²) irradiation of the 800 nm wavelength, 150 fs duration pulses was used to ablate As ₂S₃ glass. Self-organized growth of the fibers, rods, and microsphere-type structures was observed. Composition of the nano-/micro-structured material was close to that of the source As ₂S₃ glass (with up to 20% surplus of sulphur in nano-rods). Straight rods as thin as 20 nm in diameter and over 1 μm-long were obtained. Application potential of nano-/micro-structured As ₂S₃ glass is discussed.