Ricerc@Sapienza

The waveguide losses from a range of surface plasmon and double metal waveguides for Ge/Si1−xGex THz quantum cascade laser gain media are investigated at 4.79 THz (62.6 µm wavelength). Double metal waveguides demonstrate lower losses than surface plasmonic guiding with minimum losses for a 10 µm thick active gain region with silver metal of 21 cm−1 at 300 K reducing to 14.5 cm−1 at 10 K.

This paper presents the integration on the same glass substrate of an amorphous silicon photodiode and a diffused waveguide, to achieve an integrated evanescent waveguide sensor. Simulations performed with COMSOL Multiphysics show that the coupling efficiency between the waveguide and the photosensor is strongly affected by the presence of the passivation layer, and by thickness and refractive index of the transparent electrode of the photodiode. A first prototype has been fabricated using standard microelectronics techniques in a 6-masks process flow.

We present the design of an integrated optoelectronic device based on an evanescent waveguide sensor with a-Si:H photodiodes and ion-exchange diffused glass waveguides for on-chip biomolecular detection.

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.

We present detailed Monte Carlo simulations of a simple model of a nematic liquid crystal channel waveguide investigating the effect of an applied electric external field. The simulations are based on the Lebwohl-Lasher lattice spin model with boundary conditions chosen to mimic the homeotropic anchoring appropriate for PDMS polymer walls. The external field is modeled by adding an additional term to the Hamiltonian which describes its coupling to the mesogenic molecules. We have investigated the effect of the external field on the optical transmission and the ordering across the cell.

Simple Riemann waves (RWs), solutions of the Inviscid Burgers’ Equation (IBE), are of fundamental importance to study shock formation in different physical frameworks beyond hydrodynamics [1]. Recently, RW signatures in time domain have been reported in the context of nonlinear optical fibres [2-4]. Nevertheless, only limited control was demonstrated on the propagation of these peculiar optical pulses [5]. Here, we describe a method to control the nonlinear dynamics of their spatial counterpart, i.e., Riemann beams (RBs).

Here we present the design of an amorphous silicon photodetector integrated with an ion-exchanged waveguide on the same glass substrate in order to obtain an evanescent waveguide sensor for on-chip biomolecular recognition in Lab-on-Chip applications. We studied the behaviour of a monochromatic light in a channel waveguide and its coupling into the thin-film sensor, using COMSOL Multiphysics. Simulations show that the presence of the photodiode’s insulation layer and transparent electrode strongly affects the coupling efficiency between the waveguide and the sensor.

The use of liquid crystals (LC) as cladding in optical switching applications enables large phase shifts with low power consumption, due to the possibility of changing the orientation of
LC’s molecules by applying an external electric field. As a result, variations of such a driving electric field, leads to changes in the effective refractive index of the LC and, consequently, in the optical phase at the output of such waveguides. Establishing an appropriate molecular organization inside the cells is thus fundamental for the function and optimization of such devices.