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Optical frequency combs are at the center of numerous applications such as LIDAR and RADAR systems, metrology, telecommunication, and spectroscopy. Among the different ways of frequency comb generation, integrated mode-locked lasers offer lower cost, smaller footprint, and easier system integration than their bulk counterparts. In this work, we demonstrate a III-V/ $\text{S}_{\mathrm {i3}}\text{N}_{4}$ hybrid integrated mode-locked laser developed for RADAR applications to fulfill the role of a frequency bank in the RF domain. Thanks to the low-loss in silicon nitride waveguides, we were able to design a cm-long cavity that enables low noise operation with a very low repetition rate of 364 MHz, which provides high precision when generating RF frequencies. In this letter, we demonstrate passive and harmonic mode locking, with an improved electrical modulation efficiency in the active chip.

In an effort to optimize both the optical properties and chemical stability of plasmonic platforms for surface-enhanced fluorescence spectroscopy, a series of multilayered heterometallic structures were prepared. Gold–silver multilayered array of prisms were designed, where the gold layers acts as protective layers for the silver and extends the spectral range of the resulting localized surface plasmon resonances. Herein, we report an experimental study of the enhanced near-field fluorescence from quantum dots deposited at the surface of these platforms. This was performed using near-field scanning optical microscopy yielding simultaneous measurements of topographical features and near-field fluorescence of the prismatic arrays. Hence, the individual localized fluorescent hot-spots could be imaged and spatially correlated with the geometry of the nanostructures for distinct polarization configuration of the excitation light with respect to the orientation of the structures. Furthermore, the fluorescence enhancement was evaluated spatially and temporally for the series of the nanoprism platforms. In particular, the quenching of the near-field fluorescence due to the metal structures was carefully evaluated for the metal–fluorophore hybrid systems.

We report a general and simple approach to take control of the color of light-emitting two-luminophore hybrid nanowires (NWs). Our strategy is based on the spatial control at the nanoscale (coaxial geometry) and the spectral selection of the two kinds of luminophores in order to restrict complex charge and energy transfers. Thus, it is possible to control the color of the photoluminescence (PL) as an interpolation of the CIE (Commission Internationale de l’Eclairage) coordinates of each luminophore. For this purpose, we selected a green-emitting semiconducting polymer and a red-emitting hexanuclear metal cluster compound, (n-Bu4N)2Mo6Br8F6, dispersed in a poly(methyl-methacrylate) (PMMA) matrix. The great potential and the versatility of this strategy have been demonstrated for two configurations. First, a yellow PL with a continuous change along the nanowire has been evidenced when the proportion of the PPV shell versusthe nanocomposite core, that is, the green/red volumic ratio, progressively shifts from 1:2 to 1:5. Second, an extremely abrupt change in the PL color with red-green-yellow segments has been achieved. A simple model corroborates the effectiveness of this strategy. PL excitation and time-resolved experiments also confirm that no significant charge and energy transfers are involved. The two-luminophore hybrid nanowires may find widespread nanophotonic applications in multicolor emitting sources, lasers and chemical and biological sensors.