Brillouin fiber laser for signal generation from microwave-to-terahertz regimes

Flexible radio-frequency (RF) signal generation in a wide range is of great significance for the application of microwave photonics. In this work, we propose and experimentally demonstrate a dual-wavelength Brillouin fiber laser (BFL) that stably oscillates the stimulated Brillouin scattering (SBS) signals in an all-optical feedback cavity without any electro-optic or optoelectronic conversions. To effectively form the single mode, the two SBS lights outflowed from the cavity are put asunder and separately injected into their pump loop. By self-injected locking to the SBS signal rather than the laser pump as in the literature, single mode oscillation happens in the wideband of 14-300 GHz with a tunable frequency resolution of about 130 MHz. The phase noise is measured by down-converting the BFL via an optical frequency comb (OFC), which reaches below -98 dBc/Hz at 10-kHz offset frequency within 250 GHz, and -89.7 dBc/Hz@10kHz at 300 GHz, providing a widely tunable optical source for terahertz community.