Subsurface processing of GaAs by nanosecond pulses

Gallium Arsenide (GaAs) has unique properties owing to its direct band-gap, offering significant optical and electrical device opportunities, including mid-infrared photonic applications. However, due to limitations in fabrication, GaAs-based devices are essentially constrained to the wafer surface. Here, we present the first laser-induced subsurface modifications formed deep inside GaAs wafers, without damaging the crystal above or below. By exploiting various nonlinear laser interactions, we have recently demonstrated arbitrary 3D fabrication inside silicon wafers, with ~1-µm resolution [1]. Here, using a similar approach, we demonstrate formation of deeply buried laser-induced modifications in GaAs. To the best of our knowledge, this is the first “in-chip” modification of this material. The observed disruptions are in the form of nanogratings, similar in nature to nanogratings observed in various materials [2]. Such modifications can be exploited for fabricating various micro-devices using optical index changes or potentially be used for functional components such as lenses and holograms for mid-infrared applications [1].
[1] Turnali et al., Nature Photonics, 11, 639-645 (2017)
[2] Shimotsuma et al., Phys. Rev. Lett., 91, 247405 (2003)