RESUMEN
In this work, we design and experimentally demonstrate a novel terahertz (THz) filter exhibiting a flattened spectral response in the atmospheric transmission window around the central frequency of 300 GHz. The innovative concept behind this filter is the coupling of Fabry-Perot and guided mode resonances. The latter arise from a two-dimensional patch array patterned on an aluminum layer deposited on a low loss cyclo-olefin polymer. The filter experimental performance shows high transmittance in the flat-top band, with less than 3 dB losses, and high out-of-band rejection, as theoretically expected. This kind of component provides a cost-effective, functional solution for narrowband filtering in emerging THz devices and systems with possible applications in wireless telecommunications.
RESUMEN
Although the first nanoseconds to microseconds rule the resulting process yield of laser ablation in liquid, a comprehensive view involving combination of time-resolved measurement techniques is still lacking. In this paper, fundamental aspects of laser ablation of metals in water during the production of nanoparticles are discussed. Three fast diagnostic methods have been applied simultaneously. These are Optical Emission Spectroscopy for the plasma characterization, fast shadowgraph for plasma and cavitation bubble dynamics and laser scattering for the mechanisms of delivery of the produced materials in the liquid. Moreover, in order to validate the discussion, the effect on cavitation dynamics of the ablation of bulk and wire-shaped targets has been investigated together with the relative nanoparticles production yield. Unusual arrow-bow ejection phenomena between the cavitation bubble and the wire result in suppressed material back-deposition, causing efficient ejection of ablated matter into the liquid. The presented nanosecond and microsecond-resolved analysis allows estimating the timescale and role of the basic mechanisms involved in laser ablation in liquids as well as the thermodynamic characteristics of the processes.
RESUMEN
The sub-wavelength concentration and propagation of electromagnetic energy are two complementary aspects of plasmonics that are not necessarily co-present in a single nanosystem. Here we exploit the strong nanofocusing properties of stacked optical antennas in order to highly concentrate the electromagnetic energy into a 5 nm metal-insulator-metal (MIM) cavity and convert free radiation into guided modes. The proposed nano-architecture combines the concentration properties of optical nanoantennas with the propagation capability of MIM systems, paving the way to highly miniaturized on-chip plasmonic waveguiding.