Brillouin lasing featured by narrow linewidth and wide tunability has been applied to sensing, coherent communication and microwave photonics. Here, we demonstrate a cascaded Brillouin lasing in the integrated silicon racetrack microring pumped by the external fiber loop. The elaborate micro-ring can tightly confine both optical and acoustic fields, and enable the efficient generation of cascaded forward stimulated Brillouin scattering. Under the high external pump power, we observe the cascaded Brillouin lasing up to 3 Stokes order and 3 anti-Stokes order. Our experiment provides a new method to realize a cascaded Brillouin lasing in on-chip platform.
We analyze theoretically and verify experimentally a low-cost and effective scheme to realize detection of Bragg wavelength shift with high resolution based on an Erbium-doped fiber Bragg grating. The phase-shifted fiber Bragg grating is used in our experiments in order to achieve tunable single sideband modulation. Through the combination of the microwave domain and the optical domain, the Bragg wavelength shift of the grating induced by the 980-nm pump laser is translated to the amplitude variation of the beat signal generated in the photodetector. The experimental results indicate that 0.008 nm-wavelength shift is detected, which breaks out the resolution of commercial optical spectrum analyzer. Moreover, this resolution can be further improved by employing more accurate temperature and environment controlling systems. Compared with traditional optical domain detecting methods, the proposed approach shows obvious advantages in high resolution and convenient operation.