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Surface plasmon enhanced differential reflectance (DR) technique has been theoretically investigated in this paper. A plasmonic gold grating substrate is proposed to greatly enhance the sensitivity of the DR technique. The results show that the sensitivity of the technique can be enhanced by at least one order of magnitude compared to that with SiO_2 substrate (dielectric substrate) and the enhancement effect is most significant for ultra-thin films with thickness of less than 1 nm. It is further demonstrated that the technique can be also used for detecting the refractive index change of thin films with a much enhanced sensitivity.

Here we propose a scheme utilizing the double plasmon modes of gold nanorod (GNR) to efficiently enhance the fluorescence of surrounding emitters. The transversal and longitudinal surface plasmon resonance (TSPR and LSPR, respectively) modes of GNR are simultaneously utilized to enhance the excitation and emission efficiency, respectively. To demonstrate the idea, GNRs coated with an Oxazine-725 dye molecule-doped silica shell are employed. For comparison, gold nanospheres with the same shell are also studied, of which the single plasmon resonance mode matches only with the excitation wavelength of Oxazine-725. The experimental results, in agreement with theoretical simulations using the discrete dipole approximation method, successfully demonstrate the efficient excitation and emission enhancement of fluorescence assisted by the double SPRs of GNRs.

A bidirectionally pumped spectrum-presliced multiwavelength fiber source is presented. Two 980‐nm laser diodes are engaged to pump a section of erbium-doped fiber (EDF) in contrary directions. A double-pass Mach-Zehnder comb filter is utilized to filter and reflect the amplified spontaneous emission at one port of the EDF. An optical isolator is employed to guide out the multiwavelength outputs at the other end. The extinction ratio of the source is larger than 24.5 dB over the whole C band, and almost reaches 29 dB at 1530 nm. The integrated power of each channel is 0.58 mW at 1550 nm at 112.3‐mW total pump power. The channel spacing and bandwidth are 0.81 and 0.30 nm, respectively. The ratio of the forward pump power to the total pump power is best set between 0.3 and 0.4, to obtain large extinction ratio and high output power simultaneously. The source is expected to have applications in wavelength-division-multiplexing local access networks and integrated optics.