This paper reports an efficient fabrication of nanostructures on silicon substrates for surface-enhanced Raman scattering (SERS). Silicon wafer substrates in the aqueous solution of silver nitrate were machined by the femtosecond laser direct writing to achieve simultaneously in one-step the generation of grating-like nanostructures on the surface of the substrate and the formation of silver nanoparticles on the surface of the nanostructures via the laser-induced photoreduction effect. Parametric studies were conducted for the different concentrations of aqueous silver nitrate solutions and scanning speeds. The enhancement factor of the SERS is found to be higher than 10(9). The patterning technique provides an opportunity to incorporate the SERS capability in a functional microchip.

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We report a simple Fabry-Perot interferometer (FPI) embedded in a glass chip, which is capable of precisely measuring the refractive indices of liquid samples. The microdevice is the integration of a single-mode optical fiber and a microchannel in the photosensitive glass fabricated by femtosecond laser followed by thermal treatment, wet etching, and annealing. The function of the FPI is demonstrated by measuring the refractive indices of water and methanol. The interference visibility is more than 4.0 dB, which is sufficient for most sensing applications. This refractive index sensor with rigid structure could be further integrated to become a more complex 3D lab-on-a-chip for reliable biomedical applications.

The high-precision and portable nonlinear magneto-optical rotation (NMOR) atomic magnetometer has significant potential in the direction of magnetic field measurement under a geomagnetic environment. Here, we propose a single-beam NMOR atomic magnetometer with amplitude modulation based on a fiberized electro-optic modulator (EOM) for the first time, to the best of our knowledge, which provides a feasible scheme for the integrated design. A theoretical model of the system response signal as a function of the modulation amplitude is established by a Jones matrix. Based on the theoretical model, the influence mechanism of the modulation amplitude on the system response signal is further analyzed and the optimal modulation parameters can be determined. Finally, a sensitivity of 42.67 fT/Hz1/2 at 50-µT magnetic field is achieved. The proposed scheme is also applicable to other magnetometers under a geomagnetic environment.

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