Nanodiamond-Enabled Passively Q-Switched Solid-State Laser Operating at 2 μm

This work demonstrates a passively Q-switched (PQS) Tm:YAlO₃ (Tm:YAP) laser at 2 μm employing a nanodiamond (ND) saturable absorber (SA). Microstructural analysis indicates that the spin-coated ND film exhibits spherical grains and forms effective interfacial contact with the CaF₂ substrate. Employing a 5%-transmittance output coupler (OC), the ND-based SA facilitated the generation of a PQS laser. Key performance metrics include: an average output power of 367.7 mW at an absorbed pump power of 9.66 W, and a central wavelength of 1931.2 nm. Moreover, stable pulse trains exhibited a minimum pulse duration of 376.9 ns at a repetition rate of 86.27 kHz, setting a record for the shortest pulse width ever reported for ND-based PQS lasers. Under the same conditions, the beam quality factors were measured as M 2 x = 1.02 and M 2 y = 1.08. These results confirm that ND serves as an excellent modulator, showing great potential for mid-infrared pulsed laser applications.