Flat variable liquid crystal diffractive spiral axicon enabling perfect vortex beams generation.

A transparent variable diffractive spiral axicon (DSA) based on a single LC cell is presented. The manufactured DSA can be switched between 24 different configurations, 12 convergent and 12 divergent, where the output angle is varied as a function of the applied topological charge. The active area of the device is created using a direct laser writing technique in indium-tin oxide coated glass substrates.

Near-infrared, visible, and ultraviolet lidar echo emulator.

A compact and cost effective NIR-VIS-UV lidar echo emulator (LEE) was designed and manufactured as a compact breadboard. The LEE is an application specific optical pulse shaper delivering a short lidar return (echo) in the ns range overlapped with a long lidar return in the µs range with a repetition rate from 100 Hz - 500 Hz. The short echo power levels are in the range from 0.

Liquid crystal tunable claddings for polymer integrated optical waveguides.

Optical waveguides in photonic integrated circuits are traditionally passive elements merely carrying optical signals from one point to another. These elements could contribute to the integrated circuit functionality if they were modulated either by variations of the core optical properties, or by using tunable claddings. In this work, the use of liquid crystals as electro-optically active claddings for driving integrated waveguides has been explored.

An All-Organic Flexible Visible Light Communication System.

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.

Evaluation of replicas manufactured in a 3D-printed nanoimprint unit.

Nanoimprint lithography has become a useful tool to prepare elements containing nanoscale features at quite reasonable cost, especially if the fabrication elements are created in the own laboratory. We have designed and fabricated a whole nanoimprint manufacturing system and analyzed the resulting surfaces using ad hoc packages developed on an open-software AFM image analysis suite. To complete the work, a number of polymers have been thoroughly studied in order to select the best material for this implementation.

All-organic switching polarizer based on polymer waveguides and liquid crystals.

This paper reports on the design, fabrication and characterization of an all-organic photonic integrated circuit working as a switching polarizer for visible light (630nm), combining organic waveguides and liquid crystals that can be electrically driven. The device was made in commercially available epoxy by laser direct writing lithography. A device with a 2dB loss and a 20dB extinction ratio for both polarizations, was simulated; the manufactured devices proved the working principle of the design.

A 3D-printed device for polymer nanoimprint lithography.

Nanoimprint lithography (NIL) is an imprinting technique which has experienced an increasing popularity due to its versatility in fabrication processes. Commercial NIL machines are readily available achieving high quality results; however, these machines involve a relatively high investment. Hence, small laboratories often choose to perform NIL copies in a more rudimentary and cheaper way.

Thermally tunable polarization by nanoparticle plasmonic resonance in photonic crystal fibers.

A photonic crystal fiber selectively filled with silver nanoparticles dispersed in polydimethylsiloxane has been numerically studied via finite elements analysis. These nanoparticles possess a localized surface plasmon resonance in the visible region which depends on the refractive index of the surrounding medium. The refractive index of polydimethylsiloxane can be thermally tuned leading to the design of polarization tunable filters.

Electrical response of liquid crystal cells doped with multi-walled carbon nanotubes.

The inclusion of nanoparticles modifies a number of fundamental properties of many materials. Doping of nanoparticles in self-organized materials such as liquid crystals may be of interest for the reciprocal interaction between the matrix and the nanoparticles. Elongated nanoparticles and nanotubes can be aligned and reoriented by the liquid crystal, inducing noticeable changes in their optical and electrical properties.