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We experimentally show that the generation and erasure of femtosecond laser-induced periodic surface structures on nanoparticle-covered silicon inducted by irradiation with a single laser pulse (800 nm, 120 fs, linear polarization) depend on the pulse fluence. We propose that this is due to competition between periodic surface structuring originating from the interference of incident light with surface plasmon polaritons and surface smoothing associated with surface melting. Experimental results are supported by theoretical analysis of transient surface modifications based on combining the two-temperature model and the Drude model.

Abstract: The modulation of the spontaneous emission of Rhodamine 6G has been observed in one-dimensional periodic dielectric structure of dichromated gelatin film with refractive index contrast as low as 0.01. The spontaneous emission is enhanced at the band edges and inhibits in the band gap, which agree well with the theoretical analysis on the redistribution of the fractional local density of optical states.

The phase shifts of the extinction and refractive index gratings to the illumination pattern are revealed in doped polymethyl methacrylate (PMMA). The dynamic process of these shifts is studied via two-wave coupling at 351 nm. It is shown that these shifts are from the strain and the shrinkage inside the sample and accompanied with the photo-repolymerization process during the building process of the holographic grating. Such shifts will cause obvious energy exchange between the two recording beams and enough attention should be paid to the nonlocal property of the holographic gratings of the material in the application.

Real-time detection of NAD(P)H is particularly important for understanding physiological activities of neutrophils. We scrutinize the performance of weak light detection systems with electron multiplying CCDs (EMCCDs) with regard to the feasibility of valid investigations by autofluorescence NAD(P)H in single human neutrophils. The low-noise amplification facility of EMCCDs is indeed just adequate to permit detection at an irradiation level where neither quenching nor phototoxic effects occur. For demonstration, a neutrophil respiratory burst was triggered and observed in real time. Our low-intensity detection system fulfills all requirements for real-time investigations at high spatiotemporal resolution in the field of neutrophil physiology and pathology.

Different up-conversion luminescent spectra of Er^(3+) ions were observed in the oxyfluoride glass-ceramics. The ratio of two fluorides in the original compositions was modified in order to form different nanocrystals. The intensity of up-conversion luminescence increased sharply when the ratio of PbF2 and CdF2 was 40:10. The data of differential thermal analysis and X-ray diffraction were used to explain the optimization fluoride ratio. The intensity of up-conversion luminescence is not only decided by the crystallizability but also mainly related with the stoichiometric proportion of fluoride nanocrystals in the glass-ceramics.