Demonstration of forward cascaded Brillouin lasing using a silicon-based rectangular spiral microring resonator assisted by EDFA

We experimentally demonstrate the forward cascaded Brillouin lasing exploiting a silicon-based rectangular spiral microring resonator assisted by an erbium-doped fiber amplifier. To realize the enhanced Brillouin nonlinearity, the optical and acoustic fields are effectively confined by partly suspending the spiral resonator. The free spectral range is precisely designed to match the half of the Brillouin frequency shift to guarantee Brillouin laser oscillation. The fabricated spiral resonator is incorporated in a fiber loop to serve as not only a resonance-enhanced element to generate the internal pump lasing for Brillouin scattering but also a Brillouin gain medium to excite Brillouin lasing. The spiral structure allows a 0.6368 cm long resonator waveguide to be enclosed in a small footprint of 250 × 330 μm2. Four anti-Stokes and three Stokes lasing lines are obtained with the Brillouin frequency shift of about 12.0463 GHz. The proposed approach provides a potential way to implement Brillouin lasing on a silicon-based chip.