Femtosecond laser microhole drilling inside a fused silica optical fiber with optical inner surface quality

We have demonstrated femtosecond laser microhole drilling inside a fused silica optical fiber with optical inner surface quality. An optical quality microhole with a diameter of \(3\, \upmu \hbox {m}\) and a length of approximately \(35\, \upmu \hbox {m}\) was produced inside an optical fiber of a cladding diameter of \(125\, \upmu \hbox {m}\). The microhole drilling inside an optical fiber was caused as a result of plasma filamentation of focused femtosecond laser irradiation at a wavelength of 400 nm. The size of the microhole was reproduced with a ray trace of the focused laser beam with consideration of self-focusing. The optical quality of the microhole was verified by measuring the transmittance of 94 % of infrared diode emission.