Nonlinear Optical Response of SbSI Nanorods Dominated with Direct Band Gaps

Based on its excellent visible light absorption and photoelectric response capabilities, SbSI has attracted significant research attention for a wide range of applications. Despite the fact that interesting physical properties can be induced from the sophisticated band structures of SbSI, that is, either with direct or indirect band gaps, its nonlinear optical (NLO) properties are not yet fully explored. In the present work, the NLO response of SbSI nanorods is investigated by the combination of open-aperture (OA) Z-scan, pump–probe, and spatial self-phase modulation (SSPM). It is found that the synthesized SbSI nanorods possess a relatively large nonlinear absorption coefficient and a small saturable optical intensity at a wavelength of 400 nm, compared to those of other materials. More importantly, the OA Z-scan experiments suggest that the direct band gap of SbSI plays a dominant role on the NLO effects, which is further verified by the SSPM experiments. The present work suggests that the SbSI nanorods may have great potentials for optical switches and saturable absorbers.