A Tale of Two Tantalum Borides as Potential Saturable Absorbers for Q-Switched Fiber Lasers

In this paper, we analyze the performance of two tantalum-based boride (TaB and TaB2) microparticles as potential saturable absorbers for high-power fiber lasers. Both materials are ultrahigh temperature ceramics with melting points above 3000 °C, but with different crystalline structures: TaB has an orthorhombic structure (nearly isotropic), whereas TaB2 has a hexagonal structure (uniaxial, anisotropic). Despite their different crystalline structures, the microparticles have a similar low fluence attenuation (between 2.3 and 2.60 dB/μm) and modulation depths (around 2.0 dB/μm), but remarkable different saturation fluences: TaB has a saturation fluence of 160 μJ/cm2, whereas TaB2 has a saturation fluence of 110 μJ/cm2. The measured damage thresholds are 112 and 106 mJ/cm2/pulse for TaB and TaB2, respectively. When incorporated to a fiber laser, the materials produce pulses with durations of 345 ns, lower than those reported by our group in previous papers. The results show that the materials can find potential applications in high-power Q-switched lasers.