Sub-bandgap pulsed laser patterning of planar chalcogenide microphotonics

Chalcogenide based micro-devices, including integrated photonic waveguides and metasurfaces, have broad applications from mid-infrared nonlinear optical signal processing to reconfigurable photonic metasurfaces. Laser machining is a flexible and cost-effective method for lithography-free patterning and postprocessing of large scale microphotonics. In the past, patterning of chalcogenide thin film materials has been focused on dosage studies with single-point laser exposure, or laser inscription of waveguides. Little effort has been made to find how to reduce feature size or improve the optical qualities of the pattern. In this work, we use a nanosecond laser to create linear features with high refractive index contrast in chalcogenide glass thin film and compare the feature size and surface roughness to other dielectric and metal thin films. By tuning laser power and burst pulse numbers, a minimal feature size of 6 mu m and edge roughness of 3 nm can be achieved in chalcogenide phase change material thin film. Non-volatile tunabilities are demonstrated in those laser-patterned microphotonic gratings. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement