Ricerc@Sapienza

Polydimethylsiloxane (PDMS), characterized by high optical transparency and low surface energy, electric constant, and Young’s modulus, is widely recognized as an interesting, high-quality organic material for micro- and opto-fluidic functional systems. Other advantage of applying PDMS is its cheap and easy processing owning to the fact that PDMS-based photonic devices are typically fabricated with use of reliable technology based on a standard soft photolithography.

We present optoelectronic tunable and switchable devices for integrated optics based on easy-to-build optical waveguides. The devices take advantage of the spontaneous homeotropically alignment of liquid crystals (LC) molecules to the surface of a polydimethylsiloxane (PDMS) microfluidic channel (LC:PDMS). This behaviour was investigated by means of Monte Carlo simulations, which allowed to evaluate the molecular organization and ordering inside the cell.

In this paper, studies are presented on electrical tuning of optical channels formed by the PDMS-based waveguides infiltrated with a liquid crystalline material. In particular, preliminary results are demonstrated of numerical simulations demonstrating changes in optical parameters of the waveguide channels when influenced by electric field applied via flat and IPS electrodes in order to fabricate photonic switches based on optical directional couplers. The first experimental trials of sputtering the ITO layer on PDMS substrate are also shown.

In this work, the tunable properties of nematic liquid crystals are exploited in order to design a Fabry-Perot cavity (FPC) leaky-wave antenna (LWA) with beam steering capability at fixed frequency in the THz range. The considered design is a grounded dielectric slab covered with a multistack of alternating layers of low- and high- permittivity dielectric materials, consisting of nematic liquid crystals and alumina thin films, respectively. The former allows for achieving the beam-steering capability at a fixed frequency.

Liquid crystals (LC) can be successfully adopted as waveguides for photonic devices and optofluidic systems, while poly(dimethylsiloxane) (PDMS) is a cheap and easy to implement soft material which allows the making of any geometry. Modelization and making of several LC embedded in PDMS photonic devices are presented in this work. The theoretical study of the waveguides’ inner structure was performed by Monte Carlo simulations of the molecular ordering inside the microchannel.

We present photonic devices based on a nematic liquid crystals (NLC) infiltrated in polydimethylsiloxane (PDMS) channels, named LC:PDMS waveguides, for flexible photonic integrated circuits. A simulation study of the NLC ordering and possible defects under an electric field between coplanar gold electrodes has been carried out by a Monte Carlo approach.

We have performed a detailed Monte Carlo study of photonic devices based on nematic liquid crystal infiltrated in polydimethylsiloxane (PDMS) and in Silicon-Organic Hybrid (SOH) channels, to be used as waveguides. The simulations of a simple model of these slot waveguide shifters have shown the effect of an applied electric external field in two cases with different surface alignments, i.e. planar SOH and homeotropic PDMS. We have investigated the effect of the external field on the optical transmission and the ordering across the cell.

This paper reports on optical waveguides using liquid crystals (LC) as core. Such optical waveguides have the advantage to be controlled by a low voltage electric field or by using an optical beam by exploiting the highly efficient electro-optic or nonlinear optical effects, respectively. Optical switches based on LC embedded in silicon grooves have been reported with on–off contrast over 40 dB by applying about 8 V.

Metamaterials have provided applications in spectral ranges covering radio frequencies and ultraviolet. However, most applications have been extrapolated to the visible or near-infrared after being developed at the GHz level. This is due to technological reasons since fabrication of microwave antennas is not as demanding as THz resonators or plasmonic nanostructures. Accordingly, this book has been divided into three parts. In the first part, fundamentals of metamaterials and metadevices are discussed, while describing recent advances in the field.