Oxygen vacancies based BiOBr nanoflowers saturable absorber and its application in Q-switched mode-locked infrared laser

In this work, BiOBr nanoflowers with oxygen vacancies as saturable absorber are prepared using hydrothermal method. Passively Q -switched mode -locked infrared laser is achieved. The output power reaches the maximum 312 mW. The minimum Q -switched envelope is 242 ns with the maximum repetition rate of 180.5 kHz. Meanwhile, the mode -locked pulse duration within the Q -switched envelope is approximately 315 ps with repetition rate of 232 MHz. The results of X-ray diffraction (XRD), Electron paramagnetic resonance (EPR), UV-Vis-NIR diffuse reflectance spectra, and X-ray photoelectron spectroscopy (XPS) demonstrate the oxygen vacancies introduce intermediate energy levels in the energy band of BiOBr, which enhances the optical absorption in the near -infrared region. Therefore, BiOBr saturable absorber exhibits good saturable absorption characteristics in the near -infrared region and is a promising modulation element in Q -switched mode -locked infrared lasers.