In situ SERS monitoring of plasmonic nano-dopants during photopolymerization

Potential for sub-mm long erbium-doped composite silicon waveguide DFB lasers

Compact silicon integrated lasers are of significant interest for various applications. We present a detailed investigation for realizing sub-mm long on-chip laser structures operating at λ = 1.533 µm on the silicon-on-insulator photonic platform by combining a multi-segment silicon waveguide structure and a recently demonstrated erbium-doped thin film deposition technology. Quarter-wave shifted distributed feedback structures (QWS-DFB) are designed and a detailed calculation of the lasing threshold conditions is quantitatively estimated and discussed. The results indicate that the requirements for efficient lasing can be obtained in various combinations of the designed waveguide DFB structures. Overall, the study proposes a path to the realization of compact (< 500 µm) on-chip lasers operating in the C-band through the hybrid integration of erbium-doped aluminum oxide processed by atomic layer deposition in the silicon photonic platform and operating under optical pumping powers of few mW at 1,470 nm.

Magnetic assembled 3D SERS substrate for sensitive detection of pesticide residue in soil

Three-dimensional (3D) surface enhanced Raman scattering (SERS) substrates were produced by magnetic force assisting self-assembled nanoparticles in arrayed holes. Compared to '2D' plasmonic structures used in conventional SERS substrates, the 'hot spots' existed on whole depth of the 3D SERS substrates, which greatly enhanced the sensitivity. The prepared 3D SERS substrate was able to detect 4-aminothiophenol with a concentration down to 1 pM. Furthermore, the substrate was applied to detect hexachlorobenzene residue in soil, indicating its great potential for rapid and sensitive detection of extreme low concentrated molecules, especially pollutants residues in foods and environments.

Self-assembled monolayers of bimetallic Au/Ag nanospheres with superior surface-enhanced Raman scattering activity for ultra-sensitive triphenylmethane dyes detection

The bimetallic Au/Ag self-assembled monolayers (SAMs) were constructed by using mono-dispersed Au/Ag nanospheres (Ag: 4.07%-34.53%) via evaporation-based assembly strategy. The composition-dependent surface-enhanced Raman scattering (SERS) spectroscopy revealed that the Au/Ag (Ag: 16.83%) SAMs provide maximized activity for triphenylmethane dyes detection. With the inter-metallic synergy, the optimized SAMs enable the Raman intensity of crystal violet molecules to be about 223 times higher than that of monometallic Au SAMs. Moreover, the SERS signals with excellent uniformity (<5% variation) are sensitive down to 10^-13  M concentrations because of the optimal matching between bimetallic plasmon resonance and the incident laser wavelength.