Nonlinear saturable absorption properties of BP/ReS2 heterojunction and its application in 2 μm all-solid-state lasers

For 2 μm all-solid-state lasers, pulse modulation methods based on low-dimensional nanomaterial saturable absorbers (SAs) offer advantages such as compact structure, low cost, and ease of implementation. The construction of stable, highly nonlinear low-dimensional nanomaterial SAs is an urgent issue to be addressed. In this paper, two types of black phosphorus/rhenium disulfide (BP/ReS₂) heterojunction with high stability were prepared separately by liquid phase exfoliation (LPE) and mechanical exfoliation (ME) methods, the nonlinear saturable absorption characteristics of the two types of heterojunctions have been characterized in detail. Then, the pulse modulation applications of these two materials have been studied in a 2 μm all-solid-state thulium-doped yttrium aluminum perovskite (Tm:YAP) passively Q-switched pulsed laser. The BP/ReS₂ heterojunction SA prepared by the LPE method demonstrates a thinner thickness and lower non-saturation optical loss, which achieved the maximum average output power 528 mW at a pump power of 6.37 W, with a narrowest pulse width of 366 ns, and a maximum peak power of 28.85 W. These results indicate that the BP/ReS₂ heterojunction SA has great potential for optical modulation device applications.