The automated laser welding process of 2.0 mm thick sheets of AISI 304 stainless steel was investigated. The disk laser with a beam spot diameter of 200 μm was used for bead-on-plate and next for autogenous butt joints welding. The influence of basic welding parameters such as laser power, welding speed, and focal spot position on fusion zone configuration, quality of joints, microstructure changes, and microhardness distribution across the joints were analysed and presented in this paper. The results have shown that stiffening of the 2.0 mm thick sheets is crucial for providing high quality and reproducibility of butt joint in a case of AISI 304 stainless steel due to relatively low thermal conductivity and simultaneously high thermal expansion. Relevant drop of microhardness in the weld zone was observed. The mean value of microhardness of the base metal was 230 HV0.1, while the microhardness in fusion zone of the test welds was ranged from 130 to 170 HV0.1. Additionally the microstructure changes in the weld metal and also in the heat affected zone of test joints is described.

Erbium-doped lead silicate glass has been investigated for near-infrared emission and up-conversion applications. Near-infrared emission due to ⁴I_13/2 → ⁴I_15/2 transition of Er³⁺ is relatively broad (70.5 nm) and long-lived (3.7 ms). Also, up-conversion luminescence spectra of Er³⁺ ions in lead silicate glass have been examined as a function of temperature. The relative intensities of luminescence bands corresponding to ²H_11/2 → ⁴I_15/2 and ⁴S_3/2 → ⁴I_15/2 transitions of Er³⁺ were determined with temperature. The fluorescence intensity ratio and temperature sensitivity were calculated. The maximum sensitivity for Er³⁺ doped lead silicate glass is close to 26.4 × 10⁻⁴ K⁻¹ at T = 590 K.