1,721,138 research outputs found
“COL CERVIELLO ET NON CON LE MANI”. New hypotheses on the Michelangelo plaster works of the Fine Arts Academy of Perugia
No full textLiquid crystal channel waveguides for optofluidic applications
No full textThe research on the integration of optics and microfluidics, better known as optofluidics, in combination with the optical properties of liquid crystals (LC) can be used to make both electrically and optically controlled cores for switchable and reconfigurable waveguides [1-2]. Several different devices were designed, simulated, developed and characterized, achieving routing capabilities in LC waveguides with electro-optical [3-6] and all-optical [7] control, and through nematicon propagation [8].
In this paper we present our recent results on light propagation in polydimethylsiloxane (PDMS) channels with LC infiltrated core. Polarization independent light transmission was observed, despite the typical LC optical anisotropy, and we measured a transmission variation due to the orientation of the LC molecules of only 0.3 dB. The experimental results were found to be consistent with both the orientation observed under a polarizing microscope and the simulations. Polarization insensitive behavior is an interesting feature which makes the proposed LC waveguides a basic structure for low cost devices, which can be used for optical interconnections or integrated with microfluidic circuits for lab on chip and sensing applications
Polarization independent liquid crystal waveguides on flexible PDMS substrates
No full textLiquid crystals (LC) and LC-composites can be successfully used in the fabrication of photonic
devices to be employed in several applications including sensors, optical communications and
imaging systems. Components in guided-wave microstructures operating at low optical and electric
powers can be engineered and produced exploiting their excellent electro-optic, thermo-optic and
nonlinear optical responses [1].
We have investigated different technological processes to make liquid crystal photonics devices
based on silica on silicon [2-5] and glass [6,7] in order to obtain new photonic components for
optofluidics circuits [8]. Our latest research activity was focused on light propagation in
polydimethylsiloxane (PDMS) channels with LC infiltrated core. Both simulation and experimental
results confirmed the presence in such waveguides of a polarization independent light transmission.
As a matter of fact, notwithstanding LC typical optical anisotropy, the measure of transmission
variation descending from LC molecules reorientation was found less than 0.3 dB, this result being
consistent with the simulations and the observations made under a polarizing microscope. This
result together with the flexibility of the PDMS channels substrate and the absence of an alignment
layer makes the proposed LC waveguides a basic structure for low cost devices, which can be used
for optical interconnections or integrated with microfluidic circuits for lab on chip and sensing
applications
Technology of optofluidic devices based on liquid crystals
No full textIn this work we investigated, both theoretically and experimentally, the light propagation in polydimethylsiloxane (PDMS) channels with LC infiltrated core
Fabrication and Characterization of Liquid Crystal Waveguides in PDMS Channels for Optofluidic Applications
No full textWe present our recent experimental results on the fabrication and the characterization of PDMS rectangular channel waveguides infiltrated with a nematic liquid crystal. Optical characterization of waveguide structures with three different widths recently implemented are reported. The particular molecular alignment inside PDMS waveguide allows polarization independent propagation despite liquid crystal anisotropy. Soft material technology based on PDMS used to fabricate liquid crystal channel waveguides is low cost and easy to implement, allowing to obtain any geometry
Facilitating Learning Through Role Inversion: The Flipped Role Methodology with AI Integration
No full textThis paper introduces the "Flipped Role" methodology applied in the undergraduate course "Digital Communication", part of the degree program in "Media, Communication, and Society". This approach redefines traditional roles in education, assigning students the responsibility of acting as educators. They develop teaching materials, quizzes, and lessons, leveraging Generative Artificial Intelligence (GenAI) as a supportive and interactive tool. The instructor’s role shifts to that of a facilitator, guiding students through a structured, phase-based process and integrating AI tools to enhance the collaborative and engaging learning experience. The primary objective of this methodology is to explore how role reversal and active engagement with AI can support deeper comprehension, improved knowledge retention, and greater awareness of GenAI’s appropriate and responsible use. By placing students at the center of content creation and decision-making, the "Flipped Role" aims to foster a collaborative and reflective educational environment while demonstrating the practical potential of AI-enhanced active learning
Passivation buffer layer for heterojunction solar cells: a-SiOx:H and a-Si:H comparison
No full textThe achievable current in a silicon based heterojunction solar cell is a limit in its conversion efficiency. This drawback depends on the optical band-gap of the sun-lighted amorphous layers, that reduces the light spectrum reaching crystalline silicon absorber. The search for new materials to overcome this hurdle is recently focusing its attention on hydrogenated amorphous silicon oxide (a-SiOx:H), which offers effective crystalline silicon surface passivation and optical band-gap larger than the commonly used hydrogenated amorphous silicon (a-Si:H). Despite a large literature on a-Si:H deposition and treatments, a-SiOx:H film obtained by plasma-enhanced chemical vapor deposition (PECVD) is relatively new in heterojunction cell application, therefore material properties should be investigated and confirmed. To obtain a-SiOx:H film, one common technique descends from dissociation of silane in hydrogen dilution by PECVD, as for a-Si:H film, introducing CO2 as source of oxygen. This addition heavily modifies the film growth, composition and hydrogen inclusion, since the new discharge conditions influence the passivation properties and also increase the amorphous layer thermal stability [1]. Recently we studied the effect of various thermal annealing and UV light soaking on a-SiOx:H layers finding out that combining together both treatments and optimizing certain process parameters allows quality increase and stability of c-Si passivation [2] [3]. In this work is presented the comparison between two heterojunction solar cells (illustrated and described in fig.1) which differ one from another only in the front side passivation layer: a-Si:H in one case, a-SiOx:H in the other case.. We monitored lifetime and implied Voc during fabrication steps and evaluated the final I-V characteristics and quantum efficiency. Furthermore, we validated the metastability proprieties of a-SiOx:H film, previously studied on single layer [2], when adopted to fabricate a complete cell structure. In particular, we established that combination of UV light exposure and thermal treatment provides a relevant performance improvement in cells having a-SiOx:H buffer, especially when compared with a-Si:H cells. In conclusion cells with a-SiOx:H show an increase of all electrical parameters: indeed Jsc and Voc were respectively 1mA/cm2 and 20mV higher in cell with a-SiOx:H than in cell with a-Si:H. The difference in voltage was also observed before cells finalization with contacts formation, by measuring the implied Voc, which was 751mV for the structure passivated both side by a-SiOx:H (Fig.2).These results will be useful for the further optimization of a-SiOx:H/c-Si heterojunction cells fabrication process
Virtual Michelangelo. Digital survey of the plaster works of the Fine Arts Academy “Pietro Vannucci” of Perugia
No full text- …
