In this paper, the effects of oxygen vacancy and gallium vacancy on the optical and scintillation properties of undoped β-Ga₂O₃ crystal and 2.5 mol % Al doped gallium oxide were investigated. For the undoped β-Ga₂O₃, the transmittance is improved after annealing in oxygen or nitrogen atmosphere. After the introduction of Al element, the absorption cutoff appears slightly blue shift, and the band gap increases. For the undoped as-grown β-Ga₂O₃ single crystals, the decay time consists of a fast component (τ₁) of the order of nanoseconds, and two slow components (τ₂, τ₃) of tens to hundreds of nanoseconds. The contribution of the fast decay time component in the decay times is 2.78%. While for Al-doped β-Ga₂O₃, the faster (τ₁) time is 2.33 ns for the as-grown one, and the contribution is 68.02%. However, the pulse height spectrum shows that the introduction of 2.5 mol % Al will reduce the light yield of the β-Ga₂O₃ crystal.

β-Ga₂O₃ crystals have attracted great attention in the fields of photonics and photoelectronics because of their ultrawide band gap and high thermal conductivity. Here, a pure β-Ga₂O₃ crystal was successfully grown by the optical floating zone (OFZ) method, and was used as a saturable absorber to realize a passively Q-switched all-solid-state 1 μm laser for the first time. By placing the as-grown β-Ga₂O₃ crystal into the resonator of the Nd:GYAP solid-state laser, Q-switched pulses at the center wavelength of 1080.4 nm are generated under a output coupling of 10%. The maximum output power is 191.5 mW, while the shortest pulse width is 606.54 ns, and the maximum repetition frequency is 344.06 kHz. The maximum pulse energy and peak power are 0.567 μJ and 0.93 W, respectively. Our experimental results show that the β-Ga₂O₃ crystal has great potential in the development of an all-solid-state 1 μm pulsed laser.