Four-Wave Mixing in a Polarization-Maintaining Fiber Bragg Grating

We experimentally demonstrate a four-wave mixing (FWM) process in an all-fiber system. In this system, a short section of polarization-maintaining fiber containing a fiber Bragg grating is included in a laser cavity as a polarimetric mirror which separately reflects two wavelengths corresponding to orthogonal polarizations (LP₀₁(x) and LP₀₁(y)) of the core mode. Two polarized modes are lased in the cavity as the pump wave and signal wave; meanwhile, due to FWM effect, two idler waves with orthogonal polarizations are generated on either side of the two fundamental polarized modes. The proposed laser operations can deliver three states (x-polarized idler, y-polarized idler, and both them) simply by appropriately adjusting the coupling between two polarizations with the polarization controllers. The information obtained in this letter suggests that the proposed FWM system is a reliable laser wavelength conversion technique with a simplified structure.