We report here a facile approach for flexible integration of high efficiency surface enhanced Raman scattering (SERS) monitors in a continuous microfluidic channel. In our work, femtosecond laser direct writing was adopted for highly localizable and controllable fabrication of the SERS monitor through a multi-photon absorption (MPA) induced photoreduction of silver salt solution. The silver substrate could be shaped into designed patterns, and could be precisely located at the desired position of the microchannel bed, giving the feasibility for real-time detection during reactions. SEM and TEM images show that the silver substrates were composed of crystallized silver nanoplates with an average thickness of 50 nm. AFM results reveal that the substrates were about 600 nm in height and the surface was very rough. As representative tests for SERS detection, p-aminothiophenol (p-ATP) and flavin adenine dinucleotide (FAD) were chosen as probing molecules for microfluidic analysis at visible light (514.5 nm) excitation, exhibiting an enhancement factor of ∼10⁸. In addition, the combination of the SERS substrate with the microfluidic channel allows detection of inactive analytes through in situ microfluidic reactions.

It is challenging to store the exponentially increasing amount of data in the information age. The multiplexed optical data storage with merits of high data density (hundreds of terabytes/disk), low energy consumption, and long lifetime could open a new era in data storage technology. The recent progress in five-dimensional (5D) optical data storage based on anisotropic nanostructures written by femtosecond (fs) laser pulses in transparent materials reveals its potential for real-world applications, but high writing speed and density remain a major challenge. Here, we propose a method for rapid and energy-efficient writing of highly localized anisotropic nanostructures in silica glass by energy modulated megahertz-rate fs pulses. An isotropic nanovoid is initially generated with pulse energy above the microexplosion threshold and then elongated to an anisotropic nanolamella-like structure via the near-field enhancement effect by lower energy pulses, minimizing the unwanted thermal effects from megahertz-rate fs pulses. The anisotropic nanostructures are exploited for 5D data storage with a rate of 10 6 v o x e l s / s , corresponding to a demonstrated fast information recording of ∼ 225 k B / s and a potentially high-density data storage of ∼ 500 T B / d i s k .

Femtosecond laser-induced periodic subwavelength and deep-subwavelength structures (SWS; DSWS) have attracted attention due to their subdiffraction resolution of surface and inner volume patterning. Understanding of the richness of laser–matter interaction during formation of SWS and DSWS is another quest which can help to find control for nanoscale fabrication. Lack of control over SWS and DSWS formation has impacted their wider use and calls for a deeper insight into the relationship between them. Herein we present a systematic study defining a criterion for imprinting either SWS or DSWS, which is based on a competition and their mutual incompatibility discriminated by the laser fluence and pulse accumulation. Structure evolution of SWS and DSWS is highly dependent on the localized effective laser fluence, which determines the instantaneous optical permittivity by the laser-excited electrons creating an active plasma layer. The proposed universal SWS and DSWS competition mechanism involving the laser-induced plasma wave at the plasma–substrate interface ties together many previous observations and unifies the discussed mechanisms of surface nanoripple formation.

Herein, we report a facile approach for rapid and maskless production of subwavelength structured antireflective surfaces with high and broadband transmittance—direct laser interference ablation. The interfered laser beams were introduced into the surface of a bare optical substrate, where structured surfaces consisting of a micropillar array were produced by two-step laser irradiation in the time frame of seconds. A multiple exposure of the two-beam interference approach was proposed instead of multiple-beam interference to simply realize planar patterns of a high aspect ratio. Tall sinusoidal pillars were created and shaped by pulse shot number control. As an example of the application, zinc sulfide substrates were processed with the technology, from which high transmission at an infrared wavelength, over 92%, at normal incidence was experimentally achieved.