Visible light communication systems can be used in a wide variety of applications, from driving to home automation. The use of wearables can increase the potential applications in indoor systems to send and receive specific and customized information. We have designed and developed a fully organic and flexible Visible Light Communication system using a flexible OLED, a flexible P3HT:PCBM-based organic photodiode (OPD) and flexible PCBs for the emitter and receiver conditioning circuits. We have fabricated and characterized the I-V curve, modulation response and impedance of the flexible OPD. As emitter we have used a commercial flexible organic luminaire with dimensions 99 × 99 × 0.88 mm, and we have characterized its modulation response. All the devices show frequency responses that allow operation over 40 kHz, thus enabling the transmission of high quality audio. Finally, we integrated the emitter and receiver components and its electronic drivers, to build an all-organic flexible VLC system capable of transmitting an audio file in real-time, as a proof of concept of the indoor capabilities of such a system.

This paper introduces a low-cost, easy-to-manufacture, dual polarization reconfigurable reflectarray antenna based on Liquid Crystal (LC) that operates at W-band. The antenna is electrically large and is capable of independently steering the beam of two orthogonal polarizations. Two different implementations of single-layer unit cells (single resonant and multi-resonant) capable of providing suitable phase range to independently control the two RF polarizations with enough isolation have been investigated. The single resonant cell was finally used to design, manufacture and test a complete reflectarray antenna made of 55×55 elements, for which an accurate and efficient modeling of the cells was implemented. The effect of the LC bias lines is minimized by following a thorough impact study. At a cell level, the measurements validate both the modeling and the capability of the LC to be locally biased at the same cell provided that the biasing network and the resonators of each polarization are properly distributed. At an antenna level, the measurements are predicted by simulations with excellent accuracy, which validates the design and modeling process. The measured antenna shows 35° of 1D scanning range with 25dBi gain and a maximum SLL of -9dB in the entire range for both polarizations at 98 GHz.

This study presents a method to realize an optically transparent beam-steering antenna. The RF and optical features of Liquid Crystal (LC) technology are used in combination with transparent metal mesh to realize the first optically transparent reconfigurable reflectarray (RA). Since the electric field of bias and Radio Frequency (RF) signals are highly non-uniform, the LC permittivity is both anisotropic and inhomogeneous thus the behavior of LC molecules needs to be obtained for accurate modeling prior to antenna design. A unit cell consisting of metallic mesh and LC is analyzed and LC director distribution is obtained. The director data are transformed into permittivity tensors in the entire LC volume and the LC is discretized in electromagnetic simulation software to perform full-wave periodic boundary simulation to model the anisotropy and inhomogeneity. The discretized model is approximated by a single dielectric block with a new permittivity range for GT7 LC material. A 10×10 RA is fabricated and measured in terms of optical and RF performance. The measured phase shift of the unit cell is 260° when the voltage is increased from 0 V to 40 V. The measured beam scans from -10° to 50° in the E-plane and from -50 to +50 in the H-plane with a 14.35 dBi maximum gain. The prototype optical performance is also measured. The benefits and drawbacks of current RF LC mixtures are discussed. It shows that with an appropriate LC mixture optimized for both RF and optical transmission, the LC-based optically transparent antennas are a viable solution for various new applications.

Polymer based photonic devices offer the possibility cost effective roll-to-roll manufacture of photonic devices. The incorporation of luminescent dopants within a solid polymer waveguide allows for the generation of light within the device avoiding tedious mechanical light coupling. However, when a dopant is embedded in a solid matrix, depending on its concentration and the nature of materials involved, the emitted light may be quenched due to aggregation effects. In this work, thin films and ridge waveguides processed by UV-photolithography have been successfully obtained from a selection of standard photopolymerizable organic monomers, SU8, EpoCore and OrmoStamp doped with a selection of standard dyes like Rhodamine-B, Coumarin-540A and Pyrromethene-580. All structures were manufactured on glass substrates. An analysis of the solubility and optical properties including band gap energy, absorption coefficient ( $$\alpha $$α ) and fluorescence of the doped photoresists at different concentrations has been performed. Photoresists doped with Rhodamine-B shows a higher energy of indirect allowed band gap transition (2.04–2.09 eV) compared to previously reported pure Rhodamine-B thin films (1.95–1.98 eV). Fabrication protocols of dye doped photoresists covering the entire visible spectrum is established.

Tunable photonic devices based on self-organized materials like liquid crystals are opening new alternatives for photonic applications, especially when several optical functions can be implemented into one device. Beam steering devices based on liquid crystals usually work either as digital beam steerers (phase gratings), or as analog steerers (prisms). Digital steerers move laser beams to fixed positions; they cannot be tuned continuously. Analog beam steerers produce a continuous angular deviation of laser beams but with very limited deviation angles. In this paper, we developed a tunable grating prism, that can work as a prism and as a phase grating at the same time. This combination of refractive and diffractive effects is achieved with multilayer indium tin oxide (ITO) electrode matrices in a liquid crystal device. This solution is completely different from previous approaches, like blaze gratings or Fresnel configurations - the tunability range here is completely continuous, or completely stepped, or a combination of both at the same time - as there are no interpixels or dead areas in the multilayer configuration. The proposed grating prism is able to deviate a light beam to a large fixed angle by diffraction, and then fine tune the beam over small angle ranges by refraction. Additionally, the light losses produced by ITO diffraction in conventional liquid crystal gratings are significantly reduced using the layered configuration.

Liquid Crystal-based mm-wave spatially fed antennas with electronic reconfiguration are a promising solution at the higher frequencies required in next generation networks. However, one of the main drawbacks of the technology in these bands stems from the high reconfigurability times they present. Through this work, a relevant step towards overcoming the temporal problem by using Dual Frequency Liquid Crystals (DFLC) is presented. This paper details, for the first time, both the electromagnetic and temporal characterization of four commercially available DFLC mixtures in W-band, enabling their use in designing faster devices. To evaluate the experimental characterization, a reflectarray surface (made of 50x50 cells) specifically designed to achieve fast switching times with a sufficient phase range has been manufactured and measured. For this cell, a preliminary addressing technique based on overdriving has been used, exhibiting reconfigurability (rise and decay) times of 20 ms, one order of magnitude faster than the current state of the art of LC-based mm-wave planar devices. The measured results match the simulations, and reveal that a precisely designed biasing technique using overdrive must be used for DFLC-cells to achieve time reduction. Additionally, the benefits of this technology compared with other LC acceleration strategies in mm-wave are discussed.