Various changes in multilayer thin-film coatings and their substrates due to laser ablation were investigated. Absorption-type (TiO₂/SiO₂) and nonabsorption-type (HfO₂/SiO₂) multilayer coatings were irradiated with 266 nm, nanosecond laser pulses. After laser irradiation, the ablated areas were machined with a focused ion beam (FIB) and the cross sections were observed using a scanning electron microscope (SEM). For the absorption-type coating, partial delamination of the coating was observed at the boundary between the TiO₂ and SiO₂ layers in regions subjected to weak irradiation surrounding the area subjected to the irradiating laser beam. The formation of mixed molten states and partial voids inside nonablated multilayers was observed. For the nonabsorption-type coating, the formation of a modified layer on the surface of the fused-quartz substrate caused by laser ablation of the multilayers was observed. These observations provide useful guidelines for the laser processing of thin-film-coated devices.

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 In this paper, we describe a method of obtaining tungsten carbide alloy pins with diameters from 14 to 60 μm in 11 to 12 min by electrochemical machining (ECM) with an ultralow-concentration electrolyte. To improve the machining accuracy, workpiece rotation and ultrasonic washing during machining were adopted. It was found that thinner pins with better axial symmetry were obtained with such rotation and ultrasonic washing. Furthermore, the effect of electrolyte concentration was investigated using NaNO₃ aqueous solution. It was found that the adhesion of by-products to pins was reduced using NaNO₃ aqueous solution over a certain concentration and that the machining speed was improved by increasing current through an increase in electric conductivity.

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