Single-mode, tunable, 980 nm double-clad Ytterbium-doped MMI-based fiber laser

摘要

We report for the first time, a single mode, tunable, double-clad ytterbium-fiber (YDF) laser emitting in a wavelength range between 976 and 985 nm that operates using the re-imaging effect that occurs in multimode interference (MMI) devices. The system consists of an YDF with bare fiber cleaved ends. The forward end of this fiber is fusion spliced to a piece of 3 m of Samarium-doped- single-mode fiber with absorption measured at 980 nm of 0.3 dB/m, and at 1030 nm of 6 dB/m. The other end of the Sm~(+3) doped single-mode fiber is spliced to a 16.2 mm long multimode fiber (MMF) in order to induce the MMI self-imaging effect. From simulations, we found that, at this particular length, for the MMF, the light exiting will exhibit a maximum transmission for the 980 nm wavelength, while keeping a minimum for the 1030 nm wavelength. Near to the MMF facet, at a distance between 0 and 100 urn, we place a dichroic mirror which also helps in the selection of the wavelength emission. We calculated that 10 dB gain generated at 980 nm is enough to build up a laser since the total round-trip cavity losses are estimated to be 8.8 dB, whereas for the unwanted 1030nm get more than 60dB insertion loss in this setup. At the end, there is more than 1 dB for the effective gain at the preferred wavelength emission range which is enough to promote lasing at around 980 nm.