Two-photon absorption effects on raman gain in single mode As2Se3 chalcogenide glass fiber

We report ~22 dB of Raman gain in single mode As2Se 3 chalcogenide glass fiber using 15 ps optical pump pulses from 1470 nm to 1560 nm. We employ a novel technique of cross-phase modulation induced sideband amplification to map out the Raman gain spectrum of this glass, and investigate the role of both degenerate and non-degenerate (ND) two-photon absorption (TPA). We find that for materials such as As2Se 3 where the Raman gain coefficient (gR) and TPA are comparable, it is critical to know and account for the role of both of these in order to achieve appreciable Raman gain. This is highlighted by our results, where we achieve significantly higher Raman gain at the longest pump wavelength (1560 nm), despite the fact that the Raman gain coefficient itself (g R) is smallest at this wavelength. This occurs because the TPA is significantly larger for shorter wavelengths in As2Se3. We conclude, therefore, that for Raman gain applications in As2Se 3, L-band operation is strongly favored over C-band operation.