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A high-aspect-ratio microstructure in polycrystalline Zinc selenide (ZnSe) is important for waveguides and photonic crystals application. In this work, we demonstrated a successful approach for fabricating microstructure with Bessel beam inscription and etching using a mixed solution of hydrogen peroxide (H2O2) and ammonia hydroxide (NH4OH). The microstructure inscribed using the femtosecond laser back-side fabrication and selective etching, has a longitudinal length of 140 μm and a width of 12 μm. The aspect ratio of microstructures is ∼ 11.2. To showcase the potential of this technique, a rib waveguide with a longitudinal length and width of 60 μm was prepared and the rib waveguides supported a well confined mode at 1.55 μm. This process makes it possible to produce three-dimensional microstructures inside polycrystalline ZnSe, and thus offers a pathway for expanding the photonic crystal structure to the mid-to-far infrared field.

By using femtosecond-pulsed laser to ablate the larger nanosized target in liquid, stable transparent NaGdF 4 :Nd 3+ colloid has been successfully fabricated. The X-ray diffraction (XRD) spectra reveal that the colloidal nanoparticles remain the hexagonal phase crystal structure of NaGdF 4 powder target. SEM and TEM images results indicate that the size of these colloidal nanoparticles decreases sharply. FT-IR results indicate that the number of O–H and C–H groups on the surface is decreased. The emission properties of the colloid have been investigated using 794 nm pulsed wave laser radiation, and it is found that the colloid exhibits near-infrared luminescent emissions in the spectral range of 850–1400 nm, and the decay time for 4 F 3/2 → 4 I 11/2 (1058 nm) Nd 3+ ion transitions is lengthened than that of powder target, these results are probably due to the reduced nonradiative relaxation assisted by high energy oscillators. The observed near-infrared emission of the stable transparent colloid makes it a good candidate for application in liquid laser.