Ultrafast laser writing quill effect in low loss waveguide fabrication regime.

The quill effect is a laser writing phenomenon in which different fabrication effects occur, depending upon the direction of laser translation. It has not yet, to our knowledge, been studied in the low-loss-waveguide (LLW) writing regime, probably due to its very weak visibility under conventional transmission microscope in that regime. In this report, with the help of adaptive third harmonic generation microscopy, we reveal the quill effect in the LLW writing regime and show its influences on the properties of laser-written photonic integrated components, in terms of polarization-related properties in fused silica and beam-splitting ratios of three-waveguide-coupler in borosilicate glass.