With the increasing energy of high power laser devices, the laser-induced damage of optical components, especially fused quartz components, has become one of the core problems in the development of high power laser devices. Studies show that pure fused quartz glass has a high intrinsic damage threshold, but fused quartz glass will inevitably introduce a large number of subsurface damage during the process of grinding and polishing, and these subsurface damage is one of the important factors leading to the decline of laser damage resistance of optical components. It is of great significance to study the subsurface damage of solid abrasive for improving the damage resistance threshold of optical components. In this experiment, 3M's abrasive pad is used as a solid abrasive. The subsurface damage of fine grinding elements are directly observed and analyzed by combining HF pickling and optical microscopy. The results show that various subsurface damage can be detected by optical microscopy after HF pickling. Profilometer is used to measure the surface roughness of the sample, the comparative analysis of the subsurface damage of the fine grinding elements shows that the elements with solid abrasive lapping have smaller roughness when the abrasive size is the same, which has a shallower depth of subsurface damage layer correspondingly.
As a new bottom-up processing method, femtosecond laser two-photon polymerization (TPP) technology, has the advantages of simple working environment, high resolution and flexibility, which is widely used in the fields of micro-optical devices, micro-mechanical devices and micro-fluid devices. Structures with different chemical or physical properties on either side are called Janus structures. In particular, when there is difference in expansion coefficient between the two sides of the Janus structure in different external environments, the structure as a whole will show shape changes controlled by the external environment, so processing Janus structure is an important way to achieve structural deformation. The key to prepare the Janus structure is the uniformity of the diprosopic structure itself. At first, we fabricate ordinary micropillars by focusing controllable femtosecond laser into photoresist (SZ2080). Then the vacuum evaporation technology is used to transform the ordinary micropillars into Janus micropillars by steaming metal on one side of the micropillars. These Janus micropillars will have a directional bending towards the side of coating metal. This phenomenon is analyzed theoretically and simulated numerically by COMSOL, which is verified by experiments. Since the thermal expansion coefficients of different materials on both sides of the micropillar are different, these Janus micropillars have the ability to change their shapes with the change of temperature, which have potential applications in temperature drive and temperature sensing.
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