Two-color holography concept (T-CHI)

The Material Processing in the Space Program of NASA-MSFC was active in developing numerous optical techniques for the characterization of fluids in the vicinity of various materials during crystallization and/or solidification. Two-color holographic interferometry demonstrates that temperature and concentration separation in transparent (T-CHI) model systems is possible. The experiments were performed for particular (succinonitrile) systems. Several solutions are possible in Microgravity Sciences and Applications (MSA) experiments on future Shuttle missions. The theory of the T-CHI concept is evaluated. Although particular cases are used for explanations, the concepts developed will be universal. A breadboard system design is also presented for ultimate fabrication and testing of theoretical findings. New developments in holography involving optical fibers and diode lasers are also incorporated

Studies on the Generation and Detection of Orbital Angular Momentum Based on Beam-Shaping Techniques

Light carrying orbital angular momentum (OAM) has many applications ranging from optical manipulation, imaging and remote sensing, and optical communications, and can be used to perform fundamental studies in quantum mechanics and quantum information. Moreover, single photons with high-order OAM allow for increasing the amount of information carried per photon in quantum communication. This thesis describes the study of methods for the preparation and detection of OAM of light in high mode order by utilizing beam shaping techniques using spatial light modulators (SLMs). The quality of the generated high-order OAM mode is limited by optical aberrations which are induced by optical elements in realistic systems and propagation through realistic channels. In order to create and characterize the OAM modes with high quality, we investigate methods for aberration detection and correction using SLMs. These beam shaping techniques for the correction of optical aberrations allow us to generate and detect light carrying OAM with mode order ranging from l = 0 to l = 8 with good quality, and to generate high-quality superpositions of OAM modes with high mode order or in high dimensions. Furthermore, we observe low crosstalk and good levels of mode discrimination between different OAM modes of light. Our experimental setup can be applied in future studies to investigate and test different protocols in quantum information with high dimensional systems, such as high dimensional quantum state tomography

Theory and applications of free-electron vortex states

Both classical and quantum waves can form vortices: with helical phase fronts and azimuthal current densities. These features determine the intrinsic orbital angular momentum carried by localized vortex states. In the past 25 years, optical vortex beams have become an inherent part of modern optics, with many remarkable achievements and applications. In the past decade, it has been realized and demonstrated that such vortex beams or wavepackets can also appear in free electron waves, in particular, in electron microscopy. Interest in free-electron vortex states quickly spread over different areas of physics: from basic aspects of quantum mechanics, via applications for fine probing of matter (including individual atoms), to high-energy particle collision and radiation processes. Here we provide a comprehensive review of theoretical and experimental studies in this emerging field of research. We describe the main properties of electron vortex states, experimental achievements and possible applications within transmission electron microscopy, as well as the possible role of vortex electrons in relativistic and high-energy processes. We aim to provide a balanced description including a pedagogical introduction, solid theoretical basis, and a wide range of practical details. Special attention is paid to translate theoretical insights into suggestions for future experiments, in electron microscopy and beyond, in any situation where free electrons occur.Comment: 87 pages, 34 figure

Optical Fiber Communication with Vortex Modes

Internet data traffic’s capacity is rapidly reaching limits imposed by optical fiber nonlinearities [5]. Optical vortices appear in high order fiber optical mode. In this thesis, we consider multimode fibers (MMFs) that are capable of transmitting a few vortex modes. Certain types of fibers have a spatial dimension leads to space-division-multiplexing (SDM), where information is transmitted with cores of multicore fibers (MCFs) or mode-division-multiplexing (MDM), where information is transmitted via different modes of multimode fibers (MMFs). SDM by employing few-mode fibers in optical networks is expected to efficiently enhance the capacity and overcome the capacity crunch owing to fast increasing capacity demand. For generation of vortex modes, we investigate computer-generated holograms (CGHs) that are fabricated by interference technique. These components constitute the potential backbone for the high-speed network of the future. To address the capacity crunch, we study the possibility of applying modes with OAM or helicity in optical fiber communication systems. First, novel fibers (known as vortex fibers) are investigated for their maximum transmission speed and energy guiding capacities. We study the mode properties of these fibers with wave transfer matrix (T-matrix) method such that the number of guided modes, material and waveguide dispersions are determined. We optimize these fibers by changing their sizes and structures with various concentrations and types of doping for the index profile. Then an optimized profile is determined for guiding of vortex or higher order modes with a minimum total dispersion and maximum bandwidth to address the capacity crunch. During this process, the waveguide dispersion is computed from numerical results that are applied for generating fitting equations. Similarly, fitting equations are formulated for estimation of number of modes in vortex fibers. Then, the use of computer generated hologram (CGH) technique for encoding vortex modes onto signals is investigated

Development of Sound Presentation System (SPS) for Characterization of Sound Induced Displacements in Tympanic Membranes

The conventional methods for diagnosing pathological conditions of the tympanic membrane (TM) and other abnormalities require measuring its motion to an acoustic excitation for its use in a clinical environment. To obtain comprehensive quantitative diagnostic information from the motion of the entire surface of the TM, it is necessary to devise an integrated system capable of accurately recording the motion and induce an acoustic stimulus. To accomplish this goal, a sound presentation system (SPS) capable of impinging acoustic stimulus in the frequency range of 20Hz to 8 kHz at known amplitudes is synthesized in this thesis. This system is then integrated with optoelectronic digital holographic system (OEDHO) which utilizes laser interferometry to record and reconstruct phase shifted images with the help of a digital camera. The OEDHO is capable of accurately recording nanometer scale motion of the TM. The preliminary design of the SPS depends on the physical dimensions of the human ear, such as the diameter of the TM (6-9mm), depth of the ear canal (about 30mm), and also dimensions of the OEDHO system such as: diameter of tip of the otoscope head for optical access (8mm), and possible locations for integration with the OEDHO. The characteristics of the system are based on the intensity of the acoustic stimulus necessary to vibrate the TM (90-110dB SPL), and method of impinging the stimulus. To accomplish this goal, the nature of sound wave propagation through a circular pipe with known dimensions is analyzed analytically, experimentally, and by using finite element analysis (FEA). The pipe is further investigated for optimum parameters using FEA by introducing changes in the diameter (3.8mm, 6mm, 10mm), length of the pipe (30mm, 60mm, 90mm), radius of the curvature (50mm, 75mm, 100mm), and strength of the sound power source (0.2W, 0.4W, 0.6W). The comparative results provide guidelines for the design of the first version of the SPS (SPS_V1). The SPS_V1 consists of a symmetric design to impinge the acoustic stimulus towards the TM and a microphone to measure the sound pressure at the TM. The system is capable of housing a range of speakers from 2mm to 15mm in diameter. The SPS_V1 can directly interface with the standard medical speculums used for human ear testing. Also, the system is capable of interfacing with all available versions of the OEDHO. The SPS_V1 is currently being evaluated in a medical-research environment to address basic otological questions regarding TM function. The performance characterization of the system inside an artificial ear canal with two different speaker configurations is herein shown, and the potential improvements and utilization are discusse

Optical diffraction tomography: a resolution study

In the past years, optical diffraction tomography (ODT) has been used both in cell imaging and to investigate the three-dimensional refractive index (RI) of large-scale (millimetre-sized) samples. In this technique, the projections at different illumination angles are acquired through digital holography (DH) and used to estimate the complex wave fields, which can be refocused with the aid of numerical diffraction algorithms. However, real extended specimens may not completely lie on a single plane. In this case, the (refocused) projections retain a certain amount of defocus which will affect the tomographic reconstruction. For this reason, this thesis aims to study the spatial resolution of an ODT system when a point-like object is allowed to go in and out of focus and is reconstructed without numerical refocusing. Two-dimensional rotation and computational Fourier optics will be used to track and model defocus and lenses during the simulation of the projections. Spatial resolution will be assessed both qualitatively and quantitatively by numerically computing the full width at half maximum (FWHM) in relation to the maximum defocus to which a simulated point was subjected during acquisition. Lastly, deconvolution is used to remove unwanted blur

Transcranial Ultrasound Holograms for the Blood-Brain Barrier Opening

[ES] El tratamiento de enfermedades neurológicas está muy limitado por la ineficiente penetración de los fármacos en el tejido cerebral dañado debido a la barrera hematoencefálica (BHE), lo que imposibilita mejorar la salud del paciente. La BHE es un mecanismo de protección natural para evitar la difusión de agentes potencialmente peligrosas para el sistema nervioso central. No obstante, la BHE se puede inhibir mediante ultrasonidos focalizados e inyección de microburbujas de forma segura, localizada y transitoria, una tecnología empleada mundialmente. La principal ventaja es su carácter no invasivo, siendo así muy atractiva y cómoda para el paciente. Normalmente, la zona cerebral enferma se trata en su parte central empleando un único foco. Sin embargo, enfermedades como el Alzheimer o el Parkinson requieren un tratamiento sobre estructuras de geometría compleja y tamaño elevado, situadas en ambos hemisferios cerebrales. Por tanto, la tecnología actual está muy limitada al no cumplir dichos requisitos. Esta tesis doctoral tiene como objetivo el desarrollo de una técnica novedosa, basada en hologramas acústicos, para resolver las limitaciones presentes en los tratamientos neurológicos empleando ultrasonidos. Se estudian las lentes acústicas holográficas impresas en 3D, que acopladas a un transductor mono-elemento, permiten el control preciso del frente de onda ultrasónico tanto para (1) compensar las distorsiones que sufre el haz hasta alcanzar el cerebro, como (2) focalizarlo simultáneamente en regiones múltiples y de geometría compleja o formando de vórtices acústicos, proporcionando así efectividad en tiempo y coste. Por ello, la investigación desarrollada en esta tesis abre un camino prometedor en el campo de la biomedicina que permitirá mejorar los tratamientos neurológicos, además de aplicaciones en neuroestimulación o ablación térmica del tejido.[CA] El tractament de malalties neurològiques està molt limitat per la ineficient penetració del fàrmac en el teixit cerebral danyat a causa de la barrera hematoencefàlica (BHE), i així no és possible una millora de salut del pacient. La BHE és un mecanisme de protecció natural per a evitar la difusió d'agents potencialment perillosos per al Sistema Nervios Central. No obstant això, aquesta barrera es pot inhibir mitjancant una tecnologia emprada mundialment basada en ultrasons focalitzats i injeccio de microbombolles. El principal avantatge és el seu caràcter no invasiu, sent així molt atractiva i còmoda per al pacient, i permet obrir la BHE de manera segura, localitzada i transitòria. Normalment, la zona cerebral malalta es tracta en la seua part central, emprant un unic focus. No obstant això, malalties com l'Alzheimer o el Parkinson requereixen un tractament al llarg d'estructures de geometria complexa i grandària elevada, situades en tots dos hemisferis cerebrals. Per tant, la tecnologia actual està fortament limitada al no complir amb aquests requeriments. Aquesta tesi doctoral està enfocada a investigar i desenvolupar una tècnica nova, basada en hologrames acústics, per a solucionar les limitacions presents en els tractaments neurològics. Una lent acústica holograca de baix cost impresa en 3D acoblada a un transductor d'element simple permet el control precs del front d'ona ultrasònic punt per a (1) compensar les distorsions que pateix el feix en el seu camí cap al cervell, i (2) focalització simultània del feix en regions multiples i de geometria complexa, proporcionant aix un tractament efectiu en temps i cost. Per això, la investigació desenvolupada en aquesta tesi demostra la possibilitat de realitzar qualsevol tractament neurològic, a més d'aplicacions en la neuroestimulació o l'ablació tèrmica dins del camp biomèdic.[EN] Treatments for neurological diseases are strongly limited by the inefficient penetration of therapeutic drugs into the diseased brain due to the blood-brain barrier (BBB), and therefore no health improvement can be achieved. In fact, the BBB is a protection mechanism of the human body to avoid the diffusion of potentially dangerous agents into the central nervous system. Nevertheless, this barrier can be successfully inhibited by using a worldwide spread technology based on microbubble-enhanced focused ultrasound. Its main advantage is its non-invasive nature, thus defining a patient-friendly clinical procedure that allows to disrupt the BBB in a safe, local and transient manner. Conventionally, the diseased brain structure has been targeted in its center, with a single focus. However, Alzheimer's or Parkinson's Diseases do require that ultrasound is delivered to entire, complex-geometry and large-volume structures located at both hemispheres of the brain. Therefore, current technology presents several limitations as it does not fulfill these requirements. This doctoral thesis aims to develop a novel technique based on using focused ultrasound acoustic holograms to solve the existing limitations to treat neurological diseases. In this dissertation, we study 3D-printed holographic acoustic lenses coupled to a single-element transducer that allow to accurately control the acoustic wavefront to both (1) compensate distortions suffered by the beam in its path to the brain, and (2) simultaneous focusing in multiple and complex-geometry structures or acoustic vortex generation, providing a time- and cost- efficient procedure. Therefore, the research carried out throughout this thesis opens a promising path in the biomedical field to improve the treatment for neurological diseases, neurostimulation or tissue ablation applications.Acknowledgments to the Spanish institution Generalitat Valenciana, which funding grant allowed me to develop this doctoral thesis, and as well funded my research stay at Columbia University. The development of the entire thesis was supported through grant Nª. ACIF/2017/045. Particularly, the research carried out in Chapter 3 and Chapter 4 was possible thanks to and supported through grant BEFPI/2019/075. Action co-financied by the Agència Valenciana de la Innovació through grant INNVAL10/19/016 and by the European Union through the Programa Operativo del Fondo Europeo de Desarrollo Regional (FEDER) of the Comunitat Valenciana 2014-2020 (IDIFEDER/2018/022).Jiménez Gambín, S. (2021). Transcranial Ultrasound Holograms for the Blood-Brain Barrier Opening [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/171373TESI