Switchable wide-band multi-wavelength fiber laser via Brillouin random lasing resonance

Abstract

A switchable wide-band multi-wavelength Brillouin-erbium fiber laser constructed by a sub fiber loop (SFL) containing an erbium-doped fiber amplifier (EDFA) and a main fiber cavity (MFC) including a 1-km length of high nonlinear fiber (HNLF) via Brillouin random lasing resonance is proposed and experimentally investigated. The EDFA is incorporated into the sub fiber loop to boost optical power of the externally injected Brillouin pump (BP) light and Stokes wave fed back from the MFC, and the amplified BP light and Stokes wave are forward launched into the HNLF via the SFL, meanwhile, the generated Stokes wave is partially backward injected into the HNLF via the MFC, which make the Brillouin random lasing resonance of the Stokes wave form in the laser cavity. Using the proposed scheme, up to 19-orders backward-output Brillouin Stokes lines with a peak power discrepancy of less than 10 dB, and 281 stable forward-output Brillouin Stokes lines with a peak power discrepancy of less than 30 dB are obtained from the different output ports of the laser. Compared with the previous results, the backward generated Brillouin Stokes lines increase from 11 to 19 orders and the spectral-lines compositions also happen to change, and the forward generated stable Brillouin Stokes lines span over 30 nm and are extended by more than 18 nm. It is obvious that the generated Brillouin Stokes lines significant increasing should owe to the Brillouin random lasing resonance being introduced into the laser cavity. Influences of the system parameters including the BP power, EDFA pump power, and feedback power of Stokes wave on the laser lasing are investigated in detail. The proposed multi-wavelength fiber lasers can backward generate switchable Brillouin Stokes lines from 1st order to 19th order with an increasing wavelength number in turn, only by adjusting the EDFA pump power; moreover, the wavelength interval of the backward generated Brillouin Stokes lines can be switched between double- and single-Brillouin frequency shift, only by adjusting feedback power of the Stokes wave, without adding additional system configuration. A statistical analysis for the randomness of the multi-wavelength Brillouin-erbium fiber lasers is also done.