To generate a photonic nanojet outside a high refractive index microsphere illuminated by a Gaussian beam.

A non-resonant, concentrated, narrow beam of light emerging from an illuminated microlens is called a photonic nanojet (PNJ). According to currently prevailing opinion, microspheres and microcylinders are only able to generate a PNJ in their exterior when their refractive index ns (or refractive index contrast) is less than 2. In this Letter we demonstrate that a PNJ can emerge from a microsphere even when ns > 2: first by employing the laws of geometrical optics for a divergent light source; then, by using ray transfer matrix analysis, a mathematical condition for the Gaussian beam (GB) outside the high ns microsphere is derived.

Raman and Photoluminescence Spectroscopy with a Variable Spectral Resolution.

Raman and photoluminescence (PL) spectroscopy are important analytic tools in materials science that yield information on molecules' and crystals' vibrational and electronic properties. Here, we show results of a novel approach for Raman and PL spectroscopy to exploit variable spectral resolution by using zoom optics in a monochromator in the front of the detector. Our results show that the spectral intervals of interest can be recorded with different zoom factors, significantly reducing the acquisition time and changing the spectral resolution for different zoom factors.

Features and advantages of flexible silicon nanowires for SERS applications.

The paper reports on the features and advantages of horizontally oriented flexible silicon nanowires (SiNWs) substrates for surface-enhanced Raman spectroscopy (SERS) applications. The novel SERS substrates are described in detail considering three main aspects. First, the key synthesis parameters for the flexible nanostructure SERS substrates were optimized.