Generation of arbitrarily patterned polarizers using 2-photon polymerization.

Patterned polarizers are prepared using liquid crystals (LC) doped with a black dichroic dye and in combination with a linear polarizer. The pattern is achieved with a nanostructured LC alignment surface, that is generated using a two-photon polymerization direct laser write (2PP-DLW). This technique creates a pattern of high-resolution grooves in the photoresist at any arbitrary angle.

Reconfigurable perfect vortex beam generator based on a liquid crystal spiral phase plate.

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.

Generation of integer and fractional vortex beams based on liquid crystal electronically reconfigurable spiral phase plates.

The manufacturing and characterization of a large-size 72-electrode liquid crystal-based reconfigurable spiral phase plate (SPP) is presented. The SPP is addressed by a custom-made driver with 72 independent channels, which allows for the generation of any arbitrary integer or fractional optical vortex beam with topological charges ranging from -24 to +24. The 25 mm diameter device is fabricated using direct laser writing, leading to a fill factor over 99%.

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.

Design and manufacture of an all-polymeric integrated multimode interferometer for visible photonics.

This work demonstrates an integrated multimode interferometer (MMI) based on a fully polymeric platform and optimized for visible range operation. The dimensions of a 2×2 MMI are first calculated analytically and simulated using finite elements method. The devices are manufactured using two layers of negative tone photoresists.

Identification of dyes and matrices for dye doped polymer waveguide emitters covering the visible spectrum.

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.

High resolution 2D beam steerer made from cascaded 1D liquid crystal phase gratings.

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.

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.

Operational strategies in US cancer centers of excellence that support the successful accrual of racial and ethnic minorities in clinical trials.

Background: Study populations in clinical research must reflect US changing demographics, especially with the rise of precision medicine. However, racial and ethnic minority groups (REMGs) have low rates of participation in cancer clinical trials.

Methods: Criteria were developed to identify cancer centers able to accrue a higher than average proportion of REMGs into clinical trials.

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.

Rapid detection of pathogens using lyotropic liquid crystals.

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.

Dynamic multilevel spiral phase plate generator.

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.

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.

Reorientation of single-wall carbon nanotubes in negative anisotropy liquid crystals by an electric field.

Single-wall carbon nanotubes (SWCNT) are anisotropic nanoparticles that can cause modifications in the electrical and electro-optical properties of liquid crystals. The control of the SWCNT concentration, distribution and reorientation in such self-organized fluids allows for the possibility of tuning the liquid crystal properties. The alignment and reorientation of CNTs are studied in a system where the liquid crystal orientation effect has been isolated.

Nematic liquid crystal reorientation around multi-walled carbon nanotubes mapped via Raman microscopy.

We have studied the formation of topological defects in liquid crystal (LC) matrices induced by multiwalled carbon nanotubes (MWCNTs) and external electric fields. The defects are ascribable to a distortion of the LC molecular director in proximity of the MWCNT surface. The system is analyzed macroscopically using spectroscopic variable angle ellipsometry.

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.

Dispersion of anomalous azimuthal rotation and circular extinction contrast in dyed K(2)SO(4) crystals.

We present measurements of the dispersion of anomalous azimuthal rotation signals from dyed crystals that are at variance with our predictions based on a model of these effects predicated on the predominance of Rayleigh scattering from isolated dye molecules (Kaminsky et al. J Phys Chem A 107:2800-2807, 2003). Here, we extend our scattering model to include the effects of the absorption and refraction of individual dyes that are inclined in a biased manner with respect to the eigenmodes of the medium.

Assessing crystallization droplets using birefringence.

In this paper, the detection of crystalline elements in protein crystallization droplets containing precipitate is illustrated using the rotating-polarizer microscope technique. The sensitivity of this automated birefringence technique enables the detection of microcrystals in a precipitate that appears to be amorphous using traditional methods of inspection. The technique is illustrated with lysozyme and glucose isomerase.

Imaging linear birefringence and dichroism in cerebral amyloid pathologies.

New advances in polarized light microscopy were used to image Congo red-stained cerebral amyloidosis in sharp relief. The rotating-polarizer method was used to separate the optical effects of transmission, linear birefringence, extinction, linear dichroism, and orientation of the electric dipole transition moments and to display them as false-color maps. These effects are typically convolved in an ordinary polarized light microscope.

Images of absolute retardance L.Deltan, using the rotating polariser method.

Modulation techniques for measuring changes in optical birefringence, such as the rotating-polariser method (Wood & Glazer, 1980, J. Appl. Crystallogr.