
Morten Andreas GedayUniversidad Politécnica de Madrid | UPM · Centro de Materiales y Dispositivos Avanzados para TIC (Cemdatic)
Morten Andreas Geday
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Publications (159)
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...
In this paper large area flat transparent reconfigurable liquid crystal (LC) spiral diffractive lenses (SDL) are employed. These SDLs are assembled back-to-back
emulating a varifocal Fresnel lens with an optical power range of 7 diopters. The designed lens can be tuned for any desired wavelength within the visible light
spectrum. The tunability of...
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...
Tunable circular devices made of liquid crystals or other materials, like lenses, axicons, or phase plates, are often constrained by limitations in size, tunability, power, and other parameters. These constraints restrict their use and limit their applicability. In this review, a thorough study of the use of light’s orbital angular momentum in the...
Tunable circular devices made of liquid crystals or other materials, like lenses, axicons or phase plates are often constrained by limitations in size, tunability, power and other parameters. These constrains restrict their use and limit their applicability. In this review, a thorough study of the use of light orbital angular momentum in LC devices...
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 el...
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...
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 el...
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 el...
Beam expanders (BE) are optical systems that modify the diameter and angular aperture of beams. The simplest configurations consist of two confocal lenses. The lenses can be both convergent (Keplerian BE) or one divergent and one convergent (Galilean BE). In the Keplerian model, the distance between lenses is the sum of the focal distances. In the...
Liquid crystal devices are an interesting approach for electronically reconfigurable tunable photonic devices that can be used in a large number of applications. Moreover, liquid crystals have demonstrated high tolerance to harsh ionizing radiation environments, making them particularly suitable for space applications. In this work, three different...
Liquid crystal devices are an interesting approach for electronically reconfigurable photonic devices that can be used in a large number of applications. In this work, three different devices will be presented: a 2D beam steerer capable of deviating an incoming light beam with unprecedent angular resolution, a reconfigurable diffractive spiral axic...
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 –36...
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 –36...
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 writi...
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. The top layer is pat...
Vortex beams main characteristic, having a helical wavefront, plays a
crucial role in optical communications. The topological charge (TC) of the
beam, the number of twists experienced by the wavefront within a
wavelength, is a new degree of freedom that enables orbital angular
momentum multiplexing (OAM). However, vortex beams intensity distributio...
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 o...
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-resolu...
The axicon is an optical element whose main characteristic is the conversion of an incident planar wavefront into a field distribution proportional to the zero order Bessel function. In contrast to traditional lenses where light converges into the focal point, axicons focus light over a distance called depth of focus. The ability to tune this depth...
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 o...
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...
The slow response time of planar Liquid Crystal (LC)-based phase-shift metasurface and Reconfigurable Intelligent Surfaces (RIS) cells is addressed in this paper by introducing a polymer network LC (PNLC) mixture suitable at mm-wave bands. Since the conventional effective isotropic model used in optical cells for describing the PNLC is not suitable...
The use of liquid crystal materials for manufacturing tunable photonic elements has become a common practice nowadays. The effective refractive index of LCs can be controlled by external signals. A precise control of the refractive index allows the development of optical elements such as beams steerers, optical vortex generators or tunable lenses....
A new compact and cost-effective instrument for dynamic characterization of ultrawide dynamic range photodetectors is presented. The instrument is an optical pulse shaper (OPS) which has been developed as a LIDAR echo emulator (LEE). It employs a single laser diode at 1064 nm, its corresponding driver and arbitrary waveform generator (AWG), to gene...
Electrically tunable phase gratings are able to steer an incoming light beam without employing movable parts. Here, we present the design and implementation of a 2D beam steering device by cascading two orthogonal 1D liquid crystal (LC) based phase gratings, each having an array of 72 rectangular individually controlled pixels and driven by a custo...
A new concept of thin, flat, transparent variable lenses with unprecedented performance in terms of active diameter and focal distance range is presented. The diffractive lens consists of two cascaded variable liquid crystal‐based spiral diffractive lenses. Changing concertedly the topological charge changes the focal length with no mechanical moti...
The ALL project has brought together lens technology developed at a public university with an SME with experience in commercial liquid crystal electronics. The patented lens technology is based on cascading liquid crystal devices inducing optical vortices. Changing the electric addressing of the cascaded devices changes the lens focal length. The r...
In the previous chapter, we have browsed upon the optics of photographic cameras, focusing on the specific features of digital cameras and their sensors. We have also compared the camera performance with eye, including grayscale, sensitivity, dynamic range, field of view and many others. Eyes are far superior to cameras inseveral aspects, those fav...
Over the last half century, photography has evolved from photochemical reactions induced on a photosensitive film to optoelectronic devices employed in digital image. Video has done the same migration from classical film movies to optoelectronic acquisition and storage. Digitaland videocameras share optics with traditional film cameras, but the ima...
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 l...
Photonic integrated circuits (PICs) have so far got a quite modest integration level. There is a growing interest on the concept of PICs having enhanced functionality while keeping or moderately increasing their complexity. One possible route to this goal is to develop active waveguides within the PICs, by including electrooptical devices that can...
In this work, the performance of a Mach–Zehnder interferometer manufactured in silicon nitride with a liquid crystal cladding is studied. The device consists of two multi-mode interference couplers linked by two rectangular waveguides, the cladding of one of which is a liquid crystal. The structure demonstrates the potential of using liquid crystal...
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 thes...
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 (pri...
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 s...
Phase-only devices based on liquid crystals are becoming popular solutions for a high number of applications in many diverse areas. The use of an electrooptic material such as liquid crystals makes the device tunable, opening up many different possibilities of light beam manipulations: beam steering, beam shaping, modulation, focusing, generation o...
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 usi...
A Liquid Crystal Beam Steering device may be designed in either of two ways: • as a digital beam steerer (beam switches to a fixed position-phase grating) • or an analog beam steerer (continuous deviation of the beam). Analog steerers work principle is equivalent to a prisms refraction, and phase gratings, on the other hand, are diffractive element...
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...
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 devi...
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 cop...
The first steps in the development of an aptasensor for bacterial meningitis diagnosis in real time are described: slow off-rate modified aptamers (SOMAmer) selection, gravimetric sensor fabrication and functionalization of its active surface. SOMAmers polyclonal populations were generated to surface specific proteins PavA (S. pneumoniae) and FHbp...
A simple in-layer electro optical switch has been prepared by selectively curing a photocurable optical polymer with a UV laser. The core of the device is a NOA-81 multimode waveguide grown by selective laser curing. The cladding is a positive calamitic liquid crystal, which allows tunability and switching of the waveguide by external driving elect...
Policryps structures of photo-curable adhesive NOA61 and nematic liquid crystal mixture E7 have been created inside selected microchannels of photonic crystal fibers (PCF). The PCF was selectively infiltrated with the photopolymer-liquid crystal mixture for the writing of a holographic tunable grating inside specific holes of the photonic fiber. A...
Lyotropic chromonic liquid crystals (LCLC) are a kind of LCs far less known and more difficult to control than conventional thermotropic nematics. Nevertheless, LCLCs are a preferred option – often the only one– for applications where hydrophilic materials must be employed. Being water-soluble, LCLC can be used in numerous biology related devices,...
A photonic integrated circuit (PIC) or integrated optical circuit is a device that integrates multiple (at least two) photonic functions, being as such similar to electronic integrated circuits. The connections between components are made of light waveguides; these can be active themselves –i.e., light paths can be externally controlled– by using e...
Traditionally, the reproduction of patterns with micron of submicron features has been a matter of expensive microelectronic equipments and involved processes. Nanoprinting machines, usually employed for polymer castings, are a good example of these equipments. Nevertheless, it is possible to develop simple processes to make micron-size patterns in...
Photonic integrated circuits (PICs) are devices that integrate multiple photonic functions. The visible light is guided between components by light waveguides of the same order as light wavelength, i.e. 1-5μm or even less [1]. Because of the size of connections, coupling light into PICs is a challenging task previous to characterizing them. The aim...
Microbial contamination of food, water and even air supply is a permanent threat against the health of humans and livestock. This threat is particularly serious in contexts such as hospitals (Legionella contamination of air-conditioning) and in extreme situations, such as those met in the third world and in natural crisis situations where water con...
A photonic integrated circuit (PIC) or integrated optical circuit is a device that integrates multiple (at least two) photonic functions, being as such similar to electronic integrated circuits. The connections between components are made of light waveguides; these can be active themselves –i.e., light paths can be externally controlled– by using e...
Coupling light into a photonic integrated circuit (PIC) is usually the most challenging task to characterize these circuits. PIC connections between components are made of light waveguides whose section is often of the same order as light wavelength, i.e., 1-5 μm or even less. Waveguides may become active by inserting additional layers of electroop...
The Polarization Maintaing Photonic Crystal Fiber PM-1550-01 has been employed to create intermodal interferometers by splicing short (cm) portions of PCF between two single mode fiber (SMF) pigtails and PANDA fibers. It has been shown that this setup generates a intermodal interferometer. The interferometers have been made tunable by the inclusion...
Liquid crystal devices are increasingly being used in non-display applications to manufacture small devices that can be driven by low voltage electronics. LCs are low cost, light weight and avoid using mechanical components. A wide number of interesting applications involve the use of LCs for phase modulation of light. This can be done with light p...
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 ellip...
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 an...