Hybrid plasmonic photonic structures combine the plasmonic response with the photonic band gap, holding promise for utilization as optical switches and sensors. Here, we demonstrate the active modulation of the optical response in such structures with two different external stimuli, e.g. laser pulses and bacteria. First, we report the fabrication of a miniaturized (5 x 5 mm) indium tin oxide (ITO) grating employing femtosecond laser micromachining, and we show the possibility to modulate the photonic band gap in the visible via ultrafast photoexcitation in the infrared part of the spectrum. Note that the demonstrated time response in the picosecond range of the spectral modulation have an industrial relevance. Moreover, we manufacture one-dimensional photonic crystals consisting of a solution-processed dielectric Bragg stack exposing a top-layer of bio-active silver. We assign the bacterial responsivity of the system to polarization charges at the Ag/bacterium interface, giving rise to an overall blue shift of the photonic band gap.
Here we report on low-threshold blue lasing from fully-transparent nanostructured porous silicon (PSi) monolithic microcavities (MCs) infiltrated with a polyfluorene derivative, namely poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO). Single-mode blue lasing is achieved at the resonance wavelength of 466 nm, with line width of ~1.3 nm, lasing threshold as low as 5 nJ (i.e. fluence of 15 μJ/cm2), and good stability under operation (i.e. 40% decay in intensity after about 7 ×105 pulses at 50 nJ).
We describe different types of photonic structures that allow tunability of the photonic band gap upon the application of external stimuli, as the electric or magnetic field. We review and compare two porous one-dimensional (1-D) photonic crystals: in the first one, a liquid crystal has been infiltrated in the pores of the nanoparticle network, whereas in the second one, the optical response to the electric field of metallic nanoparticles has been exploited. Then, we present a 1-D photonic crystal made with indium tin oxide (ITO) nanoparticles, and we propose this system for electro-optic tuning. Finally, we describe a microcavity with a defect mode that is tuned in the near-infrared by the magnetic field, envisaging a contact-less magneto-optic switch. These optical switches can find applications in information and communications technologies and electrochromic windows.
We report a study on the excited state dynamics of two symmetric squaraine dyes, carrying different side-groups attached to the squaric ring. By means of UV-VIS absorption and time-resolved fluorescence spectroscopies, we found that the photodynamic of these functional molecules depends strongly on both the steric and electro-donating properties of the side-group.