Phase-matched cascaded Brillouin lasers via single-frequency intracavity Raman pumping

Stimulated Brillouin scattering (SBS) enables multi-frequency, high coherent laser emission due to its narrow gain bandwidth and cascaded phase matching. Using a free-space Brillouin oscillator, we systematically study its phase-matching conditions. Experimentally, intracavity Raman scattering is excited by a single-frequency laser to generate SBS. Precise control over the resonance condition between cavity modes and the Brillouin frequency shift allows accurate order control of the cascaded Brillouin laser, demonstrating continuous tuning from the 1st to 5th single-frequency order at 1.2 μm. Furthermore, by extending the Raman conversion to the 1.5 μm region, we realize spectral expansion of the multi-frequency, highly coherent laser source.