We have demonstrated a broadband waveguide polariser with high extinction ratio on a polymer optical waveguide coated with graphene oxide via the drop-casting method. The highest extinction ratio of nearly 40 dB is measured at 1590 nm, with a variation of 4.5 dB across a wavelength range from 1530 nm to 1630 nm, a ratio that is (to our knowledge) the highest reported for graphene-based waveguide polarisers to date. This result is achieved with a graphene oxide coating length along the propagation direction of only 1.3 mm and a bulk film thickness of 2.0 µm. The underlying principles of the strongly polarisation dependent propagation loss demonstrated have been studied and are attributed to the anisotropic complex dielectric function of graphene oxide bulk film.
By controlling the polarization state of a simple ring erbium-doped fiber laser with photonics crystal fiber, polarization controller (PC) and tunable band-pass filter, this paper demonstrates stable operation of narrow spacing dual-wavelength fiber laser (DWFL). The flexibility of the tunable band-pass filter and PC allows the spacing tuning of the DWFL from 80 pm up to 600 pm. Such tuning ability offers flexibility in the application of DWFL, particularly in tunable microwave generation and radio over fiber. Throughout the experiment, the DWFL shows high power stability within 0.6 dB and wavelength shift of less than 10 pm. In addition to that, it also produces a narrow linewidth optical output of 3 pm with a high signal to noise ratio of more than 60 dB.
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