A novel method of triggering fiber fuse inside glass by optical breakdown and glass drilling as its application

Abstract

Glass is a light transmissive material at room temperature. Meanwhile, glass absorbs light under high temperature. The authors have researched processing bulk glass by utilizing this characteristic. A phenomenon called fiber fuse is usually recognized as an unwelcome phenomenon that occurs in an optical fiber, making it unworkable. However, the authors previously developed a glass processing method that purposely induces the fiber fuse phenomenon in bulk glass for drilling purposes by laser irradiation of a metal foil placed on the surface of the glass. This paper introduces an alternate, novel method to trigger fiber fuse inside bulk glass without requiring the metal foil, in which optical breakdown by pulsed laser irradiation induces the fiber fuse. As a preliminary step, the optical breakdown process with pulsed laser was determined. High-speed camera observation clarified that a breakdown occurred in the vicinity of the focal point and that the generated emission disappeared within 100 μs. In the case in which both pulsed and CW lasers were applied, the emission induced by the pulsed laser did not disappear but rather extended toward the light source. In addition, numerical analyses revealed that CW laser irradiation in the high-temperature region induced by the pulsed laser caused a temperature increase in the region. The high-temperature region extended toward the light source. In addition, blind-hole drilling has been demonstrated. Although the metal foil method can be used for glass drilling, applying the novel method provides two advantages: metal foil is not required and a shorter modified area remains at the bottom of the hole.