Owing to their remarkable characteristics, two-dimensional (2D) layered, MAX phase materials have garnered significant attention in the field of optoelectronics in recent years. Herein, a novel MAX phase ceramic material (Mo₂TiAlC₂) was prepared into a saturable absorber (SA) by the spin-coating method for passively Q-switching (PQS), and its nonlinear optical absorption properties were characterized with a Tm:YAlO₃ (Tm:YAP) nanosecond laser. The structure characteristics and composition analysis revealed that the Mo₂TiAlC₂ material exhibits a well-defined and stable structure, with a uniform thin film successfully obtained through spin coating. In this study of a PQS laser by employing a Mo₂TiAlC₂-based SA, an average output power of 292 mW was achieved when the absorbed pump power was approximately 4.59 W, corresponding to a central output wavelength of 1931.2 nm. Meanwhile, a stable pulse with a duration down to 242.9 ns was observed at a repetition frequency of 47.07 kHz, which is the narrowest pulse width recorded among PQS solid-state lasers using MAX phase materials as SAs. Our findings indicate that the Mo₂TiAlC₂ MAX phase ceramic material is an excellent modulator and has promising potential for ultrafast nonlinear photonic applications.

Herein, we present a picosecond-pulsed optical vortex parametric oscillator capable of generating high-power, narrow-linewidth near- and mid-infrared optical vortex outputs. The optical parametric oscillator (OPO), consisting of a KTiOAsO₄ (KTA) crystal and a Z-shaped standing wave cavity formed by five mirrors, transferred the orbital angular momentum (OAM) of the pump field to the signal and idler fields. The transmission mechanism of the OAM within the signal singly resonantsingly-resonant KTA-OPO was investigated, and the OAM was controlled and selectively transferred among the pump, signal, and idler fields by adjusting the focus position of the pump beam on the KTA crystal. With an incident pump power of 17 W, the maximum average output power was 2.14 W at 1535 nm (signal vortex field) and 0.95 W at 3468 nm (idler vortex field), respectively, corresponding to optical conversion efficiencies of 20.8% and 9.2%. The spectral linewidths of the signal and idler vortex fields were 0.502 nm and 1.216 nm, respectively. To the best of our knowledge, this is the first instance of a picosecond-pulsed optical vortex parametric oscillator with a KTA crystal.

This study reports a novel MAX phase material, Mo₂TiAlC₂, as a passively mode-locking (PML) saturable absorber (SA) for a Tm:YAP laser operating in the 2 μm wavelength range. The systematic characterization of its nonlinear optical properties was quantitatively analyzed using I-scan methodology, demonstrating a significant modulation depth of 3.5%, which indicated strong nonlinear optical activity. Within the realm of optimal cavity conditions, a remarkable performance by the PML configuration can be discerned. A stable pulsed emission was manifested at 1937 nm, wherein an average output power reaching 620 mW was achieved. A pulse temporal span of 989.5 ps was acquired with a corresponding repetition frequency of 103.1 MHz, indicating robust mode-locked synchronization. Notably, the beam quality factors (M²) along the orthogonal spatial axes were observed with values measuring 1.12 and 1.18, respectively, indicating propagation characteristics close to those of diffraction-limited beams.

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.