Passively stabilized Brillouin fiber laser frequency combs for ultralow-noise microwave generation

Abstract

Ultralow-noise microwaves are essential in a wide variety of scientific and technological applications, such as metrology, radars, and communications. Here, we propose and demonstrate a scheme for generating an ultralow-noise microwave signal using a Brillouin optical frequency comb (OFC), which is based on the stimulated Brillouin scattering in combination with a frequency-shifted optical injection locking mechanism. The generated two intra-cavity Brillouin lasers are used as the intra-cavity pump for the eventual formation of the OFC and thus the microwave signal via the cascaded four-wave mixing process. Exploiting the cascaded narrowing effect in the Brillouin cavity assisted by the frequency-shifted optical injection locking, the proposed microwave signal source exhibits ultralow phase noise. Experimental results show that the phase noise of the microwave signal is equivalent to below −115 dBc/Hz for a 200-GHz carrier at 10 kHz offset. The system can work in stable operation without the need for any active feedback loop.

Microwave Photonic Frequency Multiplier with Low Phase Noise Based on an Optoelectronic Oscillator

“…Thus far, various photonic approaches for frequency multiplication have been proposed and demonstrated [9,10], such as optical heterodyne techniques [11,12], external modulation [13][14][15], the use of optical nonlinear effects of stimulated Brillouin scattering (SBS) [16,17], and so on. In [18], low-noise repetition-rate multiplication is obtained via harmonic injection locking and gain-saturated amplification.…”