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In the last years, in order to achieve active tuning of photonic crystals devices, the possibility to use liquid crystal inside photonic crystals has been explored. On this line of argument, in this paper, we numerically investigate a tunable T-shaped waveguide diplexer, based on a two-dimensional square lattice photonic crystal composed of silicon rods in a liquid crystals. We prove that complete splitting of the entire input wavelengths range in two sub-ranges symmetrical with respect to the middle (switching) wavelength, and propagating in right and left arms respectively, can be achieved. Moreover, changing the refractive index of liquid crystals by electro-optical effect, a tuning of switching wavelength of about 60 nm can be obtained.

Rapid detection of target bacteria is crucial issue in many areas of social interest to prevent harmful contamination for humans and the environment. Porous silicon (PSi), due to its peculiar physicochemical characteristics and well-defined optical properties, was used to fabricated a label-free PSi biosensor for bacteria detection by surface hydrosilylation and bioconjugation with Protein A.

In this work we have explored the photoluminescence signal emitted by graphene oxide (GO) nanosheets infiltrated in silanized porous silicon (PSi) matrix. A strong enhancement of the PL emitted from GO by a factor of 2.5 with respect to GO on crystalline silicon was successfully demonstrated. In addition, a weak wavelength modulation of GO photoluminescence emission was observed, resulting in very attractive aspect for its exploitation in innovative optoelectronic devices and high sensible fluorescent sensors.

Photonic crystal metamaterial can exhibit negative index properties and this behaviour is well described by a resonator model. In this work, we present the experimental evidence that a Lorentz resonator correctly reconstruct data obtained with a negative refracting Photonic Crystal (PhC) by using a standard optical technique, such as ellipsometry. In particular we show that, in the frequency range in which the effective refractive index, neff, is equal to -1, the incident light couples efficiently to the guided modes in the top surface layer of the PhC metamaterial. These modes resemble surface plasmon polariton resonances. In add we present measurements by using standard technique of prism coupling evanescent wave. Once again the presence of localized plasmon-like modes at the surface of a silicon two-dimensional photonic crystal slab is demonstrated. Also in this case, in analogy with surface plasmons supported in metals in a photonic crystal metamaterial, the electromagnetic surface waves arise from a negative effective permittivity. These results opens new strategies in light control at the nanoscale, allowing on chip light manipulation in a wide frequency range and avoiding the intrinsic limits of plasmonic structures due to absorption losses in metals. Such negative index PhC materials may be of use in biosensing applications. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

In the last years, in order to achieve active tuning of photonic crystals devices, the possibility to use liquid crystal inside photonic crystals has been explored.On this line of argument, in this paper, we numerically investigate a tunable T-shaped waveguide diplexer, based on a two-dimensional square lattice photonic crystal composed of silicon rods in a liquid crystals. We prove that complete splitting of the entire input wavelengths range in two sub-ranges symmetrical with respect to the middle (switching) wavelength, and propagating in right and left arms respectively, can be achieved. Moreover, changing the refractive index of liquid crystals by electro-optical effect, a tuning of switching wavelength of about 60 nm can be obtained.

Nanostructured materials, due to their peculiar physical and chemical properties, constitute the new class of functional supports for specific innovative applications. There is a strong competition between synthetic, man-made nanostructured materials and those coming directly from nature: the first ones can be precisely tailored by properly design and fabrication; the second ones are directly available without any cost of production. In this paper, we report our latest achievements on different materials, porous silicon, zinc oxide nanowires and diatomite powders, which belong to these categories.

We investigate the tunability of a T-shaped waveguiding diplexer, based on a two-dimensional square lattice photonic crystal ( PhC) composed of silicon rods in air and in liquid crystals ( LCs), respectively. For both devices we prove that a complete splitting of the entire input wavelength range into right and left arms respectively can be achieved. Moreover, a tuning of the switching wavelength can be obtained by changing the refractive index of silicon by the thermo-optic effect for PhCs in air, and the refractive index of liquid crystals by the electro-optic effect for PhCs in LCs.