<p>The fiber fuse phenomenon refers to the propagation of an optical discharge characterized by high temperatures and high electron density in optical fibers. This phenomenon has been applied to the drilling of bulk silica glass. In this method, hole drilling is performed by controlling the void shape generated by the fiber fuse phenomenon. This study investigated the phase distribution in the continuous-wave (CW) laser-induced high-temperature emitting region, which is critical for clarifying the void formation mechanism in glass. High-speed observations were conducted to analyze the phase distributions. The observations revealed the following phase distribution: a gas-filled void surrounded by an emitting liquid. The void was unevenly distributed in the liquid phase. Considering the temperature distribution, this uneven void distribution was attributed to the flow of the liquid phase, driven by an imbalance in the interfacial tension between the void and the surrounding liquid. Furthermore, it was found that the void was deformed by generating a pressure difference between itself and its surroundings. In particular, the pressure difference between neighboring voids leads to void merging. These findings contribute to the formation of high-aspect holes, understanding the principles underlying fiber fuses, and analysis of high-temperature, high-density plasma behavior.</p>