The detection of molecules from highly diluted solutions with a limited amount is vital for precancer diagnosis, food safety, and forensic analysis. The sensitivity and convenience of detection techniques are the primary concerns. In this study, a hybrid superhydrophobic/-philic (SH/SHL) microporous platform is designed and fabricated by a femtosecond laser to improve surface-enhanced Raman scattering (SERS) performances. Relying on the micropores fabricated at the center of SHL patterns, sediments distributed at the central regions are avoided, leading to the further enrichment of the target molecules. The engineered micropores with high identification further improve the speed of Raman tests, and the fabricated SERS substrate shows an advantage in outdoor handheld detection and automated inspection applications. The optimized SERS sensor is sufficient for attomolar-level detection (10 −17 M) of rhodamine 6G using analyte volumes of just 5 μL, corresponding to an enhancement factor of 5.19 × 10 13 . Meanwhile, a relative standard deviation of 7.48% at 10 −10 M shows the excellent uniformity of this proposed SERS platform. This work further pushes forward the practical applications of SERS technology in ultratrace molecular detections.
The realization of integrated broadband mid-infrared (MIR) lasers has enormous impacts in promoting MIR spectroscopy for various important applications. On-chip MIR supercontinuum and frequency combs have been demonstrated based on cubic nonlinearities, but unfortunately third-order nonlinear conversions inherently have low efficiencies. Here, we propose and demonstrate for the first time a χ(2) parametric integrated device based on birefringence phase matching with a high quantum efficiency and low pump threshold. In a ZnGeP2-based integrated waveguide, an octave-spanning spectrum covering 5 - 11 μm is generated through optical parametric generation. A quantum conversion efficiency of 74% as a new record in MIR parametric processes is achieved. The threshold energy is found to be as low as ~616 pJ, reduced by more than 1-order of magnitude as compared to the state-of-the-art MIR parametric conversions. Moreover, a universal and cost-effective fabrication technique for integrated nonlinear photonics is demonstrated extendable to various other χ(2) crystals.
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