Acoustic Wave Coupling in Dual-Wavelength Orthogonal Polarized Brillouin Random Fiber Laser Using Polarization-Maintaining Fiber

Acoustic wave coupling in dual-wavelength orthogonal polarized Brillouin random fiber laser (BRFL) based on polarization-maintaining (PM) fiber is characterized experimentally for the first time. Dual-wavelength BRFL is generated when the pump light is injected to the Brillouin gain PM fiber at 45 degrees from the slow axis. The dynamics of intensity and frequency of dual-wavelength and single-wavelength BRFLs are investigated. The spectrum of Pearson’s correlation coefficient between different frequencies of the dual-wavelength BRFL shows several correlation peaks due to gain competition of two spatially overlapped coupled modes induced by acoustic wave coupling. The dual-wavelength BRFL presents a lower laser frequency drift with a standard deviation of 2.55 MHz and a larger relative intensity fluctuation with a standard deviation of 0.54 compared with that of single-wavelength BRFL (3.68 MHz and 0.32), which is attributed by increased photon-phonon coupling over the Brillouin gain fiber resulting from the coupling of acoustic waves in fast and slow axis due to 45 degrees pumping. In addition, replica symmetry breaking (RSB) is observed in dual-wavelength BRFL due to the increased gain competition of more random modes from acoustic wave coupling, which leads to correlated intensity fluctuations from trace to trace. The exploration of the internal spectral correlation, intensity fluctuation, RSB and frequency drift exposes the acoustic wave coupling in the dual-wavelength Brillouin random lasing process.