Violet Phosphorus Saturable Absorbers Employed for Generating High-Repetition-Rate Pulse Lasers in 1.0 μm and 1.9 μm

Compared to black phosphorus (BP), violet phosphorus (VP) exhibits higher carrier mobility and better oxidation resistance, showing great promise in the field of passive Q-switching. In this work, two-dimensional (2D) VP nanosheets were successfully prepared using the liquid phase exfoliation (LPE) method. Their nonlinear optical properties and saturable absorption characteristics were investigated through non-degenerate pump-probe techniques, Z-scan and I-scan measurements, demonstrating that they meet the essential requirements for high-performance passive Q-switches. Furthermore, the prepared 2D VP nanosheets were employed as saturable absorbers (SAs) in all-solid-state lasers to achieve passive Q-switching operation. With slight adjustment, passive Q-switched pulse outputs were realized at working wavelengths of 1.0 μm and 1.9 μm, with repetition rates of 1.1 MHz and 124.1 kHz, respectively. This represents the highest pulse repetition frequency achieved to date for 2D VP nanosheets employed as passive Q-switches in the 1.0 μm and 1.9 μm, highlighting the excellent optical modulation performance of 2D VP nanosheets and further demonstrating their tremendous potential in the field of all-solid-state ultrafast photonics.