Near infrared amplified spontaneous emission in a dye-doped polymeric waveguide for active plasmonic applications

Near-infrared amplified spontaneous emission (ASE) from an optically-pumped dye-doped polymeric slab waveguide, consisting of IR-140 in PMMA on a glass substrate, has been characterised. The ASE gain was measured using the variable stripe length method. Linewidth narrowing with increasing pump intensity was observed, indicating ASE gain in this material. The effects of the dye concentration and pump intensity on the gain were investigated under linear operation. The maximum achieved gain coefficient is γ ~68 cm(-1) for a film with 0.8 wt % of IR-140 to PMMA for a pump intensity of 43.4 mJ/cm(2). The polarisation dependence of the ASE gain was also investigated by measuring the gain coefficient of orthogonal TE and TM modes and varying the pump polarisation relative to the amplifier length. It was observed that there is some degree of gain anisotropy when the pump polarisation is aligned perpendicular to the length, but that the gain was isotropic when the pump polarisation is aligned parallel the length. The applicability of IR-140 doped PMMA for active plasmonic applications is discussed.