The design and characterisation of a reconfigurable multi-level spiral phase plate is shown. The device is based on a pie-shape liquid-crystal structure with 24 slices driven by custom electronics that allow independent excitation control of each electrode. The electrooptical cell was manufactured using maskless laser ablation lithography and has shown an unprecedented high fill factor. The topological charge can be dynamically changed between 1, 2, 3, 4, 6, 8 and 12. The device has been calibrated and characterised at 632.8 nm but can be employed at any wavelength in the visible and near infrared spectrum, just modifying the driving parameters of the electrodes. The experimental results have been compared to predictions derived from simulations. An excellent correspondence between theoretical and experimental result has been found in all cases.

Lyotropic liquid crystals play an important role in many biological environments, such as micelles, liposomes, and phospholipid bilayers of cell membranes. In this work, we explore the performance of lyotropic liquid crystals as biosensors for macromolecules, proteins and whole microorganisms in hydrophilic media, i.e., the natural media where these specimens exist. The aim is to detect specific targets employing simple, unpowered sensors that can be used in the field, with minimum additional equipment. A number of different structures have been explored. The novelty in this work is the inclusion of a new optical effect, flow enhanced amplification, that allows for the semiquantitative detection of microscopic targets in lyotropic liquid crystal cells using the naked eye only.

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.

Optical beam steering (BS) has multiple applications in fields like target seeking and tracking, optical tweezers, billboard displays and many others. In this work, a two-dimensional beam deflector based on blaze gratings is presented. Phase-only 1D blaze gratings have been prepared using maskless Direct Laser Writing (DLW) resulting in high-resolution structures in indium-tin oxide (ITO) coated glass wafers. The device is composed of two identical 1D liquid crystal (LC) cells cascaded orthogonally back-to-back, with a resultant active area of 1.1 × 1.1 mm². The 1D cells have been prepared with 144 pixels each with a 7.5 µm pitch. The total 288 pixels are driven by a custom made 12-bit Pulse Width Modulation (PWM) electronic driver, allowing for an arbitrarily high resolution. The system performance is documented, and the efficiency of the system has been tested. A maximum diagonal steering angle of ± 3.42° was achieved.

A transmissive adaptable optical setup to generate a range of perfect vortex beams (PVBs) carrying different topological charges (TC) without using moving parts is presented. The setup is composed of an ad hoc transparent reconfigurable liquid crystal (LC) spiral phase plate (SPP), a refractive axicon and a convergent refractive lens. The LC SPP electrodes are manufactured ablating indium-tin oxide (ITO) glass substrates using direct laser writing (DLW) resulting in a very high fill factor device. In-house tailored electronics drive the 72 LC SPP electrodes giving rise to 72 different configurations with orbital angular momentum. In this work, the generation of PVBs with 36 positive or 36 negative TCs using this optical setup is accomplished.