Enhanced broadband nonlinear optical properties of copper-functionalized SnSe nanosheets for laser pulse generation

Two-dimensional (2D) tin selenide (SnSe) nanosheets have emerged as promising candidates for photonic applications due to their suitable bandgap and excellent optical properties in the broadband infrared region. However, their low carrier mobility and thermal conductivity limit their expanded applications. Here, we demonstrate enhanced nonlinear optical (NLO) performance of SnSe nanosheets via copper (Cu) functionalization, which enhances carrier mobility and electronic properties. The Cu-functionalized SnSe (Cu-SnSe) exhibits superior saturable absorption characteristics with larger modulation depth and nonlinear absorption coefficients compared to pristine SnSe across broadband infrared wavelengths. Open-aperture Z-scan measurements reveal nonlinear absorption coefficients of −9.52 cm/MW and −4.44 × 10 4 cm/MW at 1.06 μm and 2.8 μm, respectively, representing significant improvements over pristine SnSe. When used as SAs in passively Q-switched (PQS) solid-state lasers, Cu-SnSe enables stable pulse generation with durations of 308 ns at 1.06 μm and 380 ns at 2.8 μm, and repetition rates of 1.29 MHz and 90.3 kHz, respectively. The enhanced NLO performance is attributed to Cu-induced lattice modifications that optimize carrier dynamics and recovery times. These results demonstrate the potential of metal functionalization strategies for advancing 2D material-based photonic devices.