Diode-pumped passively Q-switched Tm:YAP laser using a HfSe2/CsPbBr3 heterostructure as the saturable absorber

• This study introduces a new HfSe 2 /CsPbBr 3 heterostructure SA that integrates the strong NIR absorption and suitable bandgap of HfSe 2 with the excellent optical stability and high absorption coefficient of inorganic CsPbBr 3 perovskites. The heterostructure provides enhanced nonlinear optical interactions through efficient interlayer charge transfer enabled by its Type-II band alignment. By combining the intrinsic advantages of both materials, this SA offers improved modulation depth, reduced saturation intensity, and accelerated carrier dynamics compared with its single-component counterparts, making it a promising candidate for high-performance pulsed laser systems. • Using the fabricated HfSe 2 /CsPbBr 3 nanosheet SA, a diode-pumped Tm:YAP laser operating at 2 μm successfully achieved stable PQS operation with significantly enhanced output characteristics. At an absorbed pump power of 12.9 W, the system produced a minimum pulse width of 687.2 ns, a maximum pulse repetition rate of 112.82 kHz, and a single-pulse energy of 18.6 μJ. These results demonstrate superior Q-switching performance compared to lasers employing individual HfSe 2 or CsPbBr 3 SAs, verifying the synergistic advantages of the heterostructure design. • The HfSe 2 /CsPbBr 3 heterostructure produces a staggered Type-II band alignment that promotes efficient carrier separation and interlayer charge transfer, generating a built-in electric field at the interface. This interfacial coupling significantly strengthens the nonlinear absorption behavior, resulting in increased modulation depth and faster recovery dynamics. These mechanisms are responsible for the improved saturable absorption performance observed experimentally and highlight the importance of engineered heterostructures in overcoming the intrinsic limitations of traditional 2D saturable absorbers. • The successful integration of TMDC and perovskite materials in a van der Waals heterostructure establishes a new pathway for designing high-efficiency SAs for mid-infrared pulsed laser technologies. This work not only demonstrates the practical viability of HfSe 2 /CsPbBr 3 as an advanced optical modulator but also offers insights into material engineering approaches that leverage interlayer coupling to boost nonlinear responses. The output characteristics demonstrated: narrower pulse widths, higher peak power, and improved pulse stability—confirm the heterostructure’s strong potential for next-generation compact and high-power 2 μm laser sources. In this paper, a HfSe 2 /CsPbBr 3 heterostructure was prepared and used as a saturable absorber (SA) to modulate a Tm:YAP laser. Under continuous-wave operation, the Tm:YAP crystal was pumped with a diode laser at an absorbed pump power of 12.9 W, producing an output power of 2.35 W at 1995.9 nm and a slope efficiency of 23.2 %. In passively Q-switched mode, the HfSe 2 /CsPbBr 3 heterostructure SA modulated the Tm:YAP laser, resulting in an average output power of 2.1 W and a pulse width of 687.2 ns at 1987.5 nm, with a pulse repetition rate of 112.82 kHz. These parameters correspond to a slope efficiency of 19.8 %, a single-pulse energy of 18.6 µJ, and a peak power of 27.1 W.