## 3 Results and Discussion
In order to optimize the laser sealing process, the microscopic photos of different stages are shown in Figure 9 as a function of sealing cycle and plate temperature. In the reference study [32], [PERSON] et al. reported that screen printed glass frit based on V\({}_{2}\)O\({}_{5}\) and TeO\({}_{2}\) glass had a thickness of \(\sim\)20 \(\mu\)m and width of 700 \(\mu\)m. It was found that the optimized laser sealing conditions were under laser power of 40 W, laser scan velocity of 300 mm/s, and laser scanning cycle of 200. Compared to the above study, two parameters were modified in the present investigation because the fiber type of sealant had a 180 \(\mu\)m diameter. First, the glass substrates were thermally treated in the temperature range of 130-220 \({}^{\circ}\)C for 30 min using hot plates in order to reduce thermal shock after the laser sealing process. Secondly, laser scan velocity was reduced to 40 mm/s after fixing laser power of 35 W. The fiber sealant was not melted at all in the microscopic photos when the glass substrate was below 100 \({}^{\circ}\)C, until the laser scanning cycle of 200, and then it looks like delamination. The fiber sealant started to melt when the glass substrate was at a temperature of 130 \({}^{\circ}\)C with a laser scanning cycle of 200. However, it has thermal stress cracks. When two FTO glass substrates were heated at 190 \({}^{\circ}\)C, the fiber sealant was completely melted at a laser scanning cycle of 200-300, showing crack free surface. The fiber sealant was melted and aggregated showing a sphere type of island of glass molts (pores) regardless of laser scanning cycle of 200-300 after two FTO glass substrates being heated at 220 \({}^{\circ}\)C. It was found that two FTO glass substrates using the glass fiber were successfully sealed under laser power of 35 W, laser scan velocity of 40 mm/s, laser scanning cycle of 200-300, and a preheating of 190 \({}^{\circ}\)C, resulting crack free surface. Figure 10a shows a schematic diagram of jig mounted FTO substrates. Figure 10b depicts a universal tensile tester mounted with jig to investigate the laser sealing quality. The strength tests are essential to assess the mechanical resistance of the devices. The laser-sealed FTO substrates with fiber sealant were subjected to mechanical strength using equipment comprising of two stainless steel jigs up and down. Figure 10c shows tensile load changes with time for the laser-sealed FTO substrates using fiber type sealant. It can be observed from Figure 10c that under laser power of 35 W, laser scan velocity of 40 mm/s, laser scanning cycle of 200, and a preheating of 190 \({}^{\circ}\)C, uniform relative movement occurred to the fiber sealant and FTO substrates with the testing machine, which had a uniform linear motion, until the breaking force reached the maximum value, at which time the relative displacements of the sealant and FTO substrates were small. The fracture failure mode is ductile fracture, since the fracture of the laser sealing is flush and bright and perpendicular to the direction of the normal stress. The results showed that the maximum load that the samples can withstand is 110 N. This means that the fiber sealant can withstand to a strength of 41 MPa. Sealing stress was not measured on laser-sealed FTO substrates thermally treated at 130 and 220 \({}^{\circ}\)C due to defects of delamination and aggregation. It was found that the maximum value of the breaking force was reached  
Figure 2:3 (a) Glass ingot; (b) microscope image of glass fiber with 180 \(\mu\)m diameter; and (c) glass fiber spool of 1 wt% CuO-2 wt% Na\({}_{2}\)CO\({}_{3}\) codoped PSAB system. after a certain displacement between upper FTO substrate and lower FTO substrate was formed. In the previous studies, it was reported that sealing strength using screen printed sealant was observed in the range of 12.3-20.5 MPa [3,33]. Compared with values obtained from previous studies above, a sealing strength of 41 MPa seemed to be as strong a candidate as laser sealant.