Germanium-based ternary chalcogenide : an emerging low-dimensional material for nonlinear optics and ultrafast photonics

Abstract

GeSeTe; a ternary 2D chalcogenide with remarkable properties including great environmental stability, tunable bandgap, and phase-changing characteristics, shows competing prospects for advanced photonics and optoelectronic devices. Herein, the rigorous investigation of thickness dependent nonlinear optical (NLO) responses asserts intriguing outcomes highlighting strong saturable absorption (SA) property (β≈ -3.1 to -7.2 × 103 cm/GW) with the decrease in thickness (from ∼68 nm to <10 nm). Additionally, the evolution of β with input intensity and wavelength (transition from SA (at 1067.5 nm) to RSA (at 1557.5 nm)) explicitly manifests promising and wide-ranging prospects of GeSeTe in Nonlinear optics and advanced photonics. Furthermore, for the first time, ultrafast carrier dynamic response of GeSeTe-nanosheets is observed using transient absorption spectroscopy, complementing the strong nonlinear responses obtained from z-scan method. The standout SA response of GeSeTe nanosheets is also leveraged in ultrashort pulse generation, marking the first ever reported use of GeSeTe as a saturable absorber for achieving one of the narrowest pulse widths of 1.017 ps and 531 fs with high signal-to-noise ratios of 65.05 dB and 61.14 dB for 1 µm and 1.5 µm systems respectively. These results accentuate GeSeTe's significant potential as a promising NLO material for cutting edge photonics and optoelectronics devices.