Search

Extending the photon energy range of bright high-harmonic generation to cover the entire soft X-ray region is important for many applications in science and technology. The concept of critical ionization fraction has been essential, because it dictates the maximum driving laser intensity that can be used while preserving bright harmonic emission. In this work, we reveal a second, nonadiabatic critical ionization fraction that substantially extends the maximum phase-matched high-harmonic photon energy, that arises due to strong reshaping of the intense driving laser field. We validate this understanding through a systematic comparison between experiment and theory, for a wide range of pulse durations and driving laser wavelengths. In particular, high harmonics driven by intense few-cycle pulses experience the most pronounced spectral reshaping, significantly extending the bright photon energy range. We also present an analytical model that predicts the spectral extension that can be achieved for different driving lasers. This reveals an increasing role of nonadiabatic critical phase matching when driven by few-cycle mid-infrared lasers. These findings are important for the development of high-brightness soft X-ray sources for applications in spectroscopy and imaging., Comment: 18 pages, 4 figures

Funding European Research Council (851201); Ministerio de Ciencia de Innovación y Universidades, Agencia Estatal de Investigaci ́on and European Social Fund (PID2019106910GB-I00, RYC-2017-22745); Junta de Castilla y León and FEDER Funds (SA287P18); Université ParisSaclay (2012-0333TOASIS, 50110000724-OPTX, PhOM REC-2019-074-MAOHAm); Conseil Régional, I ˆle-de-France (501100003990); Barcelona Supercomputing Center (FI2020-3-0013)., Vigorous efforts to harness the topological properties of light have enabled a multitude of novel applications. Translating the applications of structured light to higher spatial and temporal resolutions mandates their controlled generation, manipulation, and thorough characterization in the short-wavelength regime. Here, we resort to high-order harmonic generation (HHG) in a noble gas to upconvert near-infrared (IR) vector, vortex, and vector-vortex driving beams that are tailored, respectively, in their spin angular momentum (SAM), orbital angular momentum (OAM), and simultaneously in their SAM and OAM. We show that HHG enables the controlled generation of extreme-ultraviolet (EUV) vector beams exhibiting various spatially dependent polarization distributions, or EUV vortex beams with a highly twisted phase. Moreover, we demonstrate the generation of EUV vector-vortex beams (VVB) bearing combined characteristics of vector and vortex beams. We rely on EUV wavefront sensing to unambiguously affirm the topological charge scaling of the HHG beams with the harmonic order. Interestingly, our work shows that HHG allows for a synchronous controlled manipulation of SAM and OAM. These EUV structured beams bring in the promising scenario of their applications at nanometric spatial and sub-femtosecond temporal resolutions using a table-top harmonic source.

The extreme nonlinear optical process of high-harmonic generation (HHG) makes it possible to map the properties of a laser beam onto a radiating electron wave function and, in turn, onto the emitted x-ray light. Bright HHG beams typically emerge from a longitudinal phased distribution of atomic-scale quantum antennae. Here, we form a transverse necklace-shaped phased array of linearly polarized HHG emitters, where orbital angular momentum conservation allows us to tune the line spacing and divergence properties of extreme ultraviolet and soft x-ray high-harmonic combs. The on-axis HHG emission has extremely low divergence, well below that obtained when using Gaussian driving beams, which further decreases with harmonic order. This work provides a new degree of freedom for the design of harmonic combs—particularly in the soft x-ray regime, where very limited options are available. Such harmonic beams can enable more sensitive probes of the fastest correlated charge and spin dynamics in molecules, nanoparticles, and materials., The JILA team graciously acknowledges support from the Department of Energy BES Award No. DE-FG02-99ER14982 for the experimental implementation, a MURI grant from the Air Force Office of Scientific Research under Award No. FA9550-16-1-0121 for the mid-infrared laser soft x-ray research, and a National Science Foundation Physics Frontier Center grant PHY-1734006 for theory. N.J.B. acknowledges support from National Science FoundationGraduate Research Fellowships (grant no. DGE-1650115). Q.L.D.N. acknowledges support from National Science Foundation Graduate Research Fellowships (grant no. DGE-1144083). J.S.R., L.P., and C.H.-G. acknowledge support from Ministerio de Ciencia e Innovación (FIS2016-75652-Pand PID2019-106910GB-I00). This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement no. 851201). J.S.R., L.P., and C.H.-G. also acknowledge support from Junta de Castilla y León FEDER funds (project no. SA287P18). L.R. acknowledges support from Ministerio de Educación, Cultura y Deporte (FPU16/02591). C.H.-G. acknowledges Ministerio de Ciencia, Innovación, y Universidades for Ramón y Cajal contract (RYC-2017-22745), cofunded by the European Social Fund. L.R., J.S.R., L.P., and C.H.-G. thankfully acknowledge the computer resources at MareNostrum and the technical support provided by Barcelona Supercomputing Center (FI-2020-3-0013).

Ultrafast laser pulses provide unique tools to manipulate magnetization dynamics at femtosecond timescales, where the interaction of the electric field -- such as excitation of spin carriers to non-equilibrium states, generation of localized charge currents, demagnetization, or inverse Faraday effect -- dominates over the magnetic field. Recent proposals using structured laser beams have enlightened the possibility to generate intense femtosecond magnetic fields, spatially isolated from the electric field. Here we demonstrate the relevance of this novel scenario to femtomagnetism, unveiling the purely precessional, non-linear, chiral response of the magnetization when subjected to circularly polarized magnetic fields. This fundamental result not only opens an avenue in the study of laser-induced ultrafast magnetization dynamics, but also sustains technological implications as a route to promote all-optical non-thermal magnetization switching both at shorter timescales -- towards the attosecond regime -- and at THz frequencies.

Symmetries and conservation laws of energy, linear momentum and angular momentum play a central role in physics, in particular in nonlinear optics. Recently, light fields with non trivial topology, such as polarization M\"obius strips or torus-knot beams, have been unveiled. They cannot be associated to well-defined values of orbital and spin angular momenta (OAM and SAM), but are invariant under coordinated rotations, i.e. rotational symmetries that are generated by the generalized angular momentum (GAM) operator, a mixture of the OAM and SAM operators. The discovery of the GAM, which at variance with integer-valued OAM and SAM, can have arbitrary value, and raises the question of its conservation in nonlinear optical processes. By driving high harmonic generation with a polarization M\"obius strip and implementing novel OAM characterization methods in the XUV range, we experimentally observe the conservation of the GAM, each harmonic carrying a precise half-integer GAM charge equal to that of the fundamental field multiplied by the harmonic order. The GAM is thus revealed as the appropriate quantum number to describe nonlinear processes driven by light fields containing topological polarization singularities., Comment: 4 figures in the main text and 13 in the supplemental document

Memoria ID-040 Ayudas de la Universidad de Salamanca para la innovación docente, curso 2020-2021.

The extreme nonlinear optical process of high-harmonic generation (HHG) makes it possible to map the properties of a laser beam onto a radiating electron wavefunction, and in turn, onto the emitted x-ray light. Bright HHG beams typically emerge from a longitudinal phased distribution of atomic-scale quantum antennae. Here, we form a transverse necklace-shaped phased array of HHG emitters, where orbital angular momentum conservation allows us to tune the line spacing and divergence properties of extreme-ultraviolet and soft X-ray high harmonic combs. The on-axis HHG emission has extremely low divergence, well below that obtained when using Gaussian driving beams, which further decreases with harmonic order. This work provides a new degree of freedom for the design of harmonic combs, particularly in the soft X-ray regime, where very limited options are available. Such harmonic beams can enable more sensitive probes of the fastest correlated charge and spin dynamics in molecules, nanoparticles and materials., Comment: Submitted to Science Advances

Datos de investigación en: http://hdl.handle.net/10366/148373, Few-electron atoms interacting with electromagnetic fields provide for privileged scenarios for disentangling elemental correlation mechanisms. We demonstrate that high-order harmonic generation (HHG) from neutral helium presents a distinctive trace of correlation back reaction in the electron dynamics prior to ionization. We identify a mechanism in which the field interacts with one of the electrons, while the second is excited to a Rydberg level through the Coulomb interaction. As back response to this correlated excitation, the first electron is knocked down to a lower level, from which it ionizes to generate high-order harmonics. Unlike other multielectron phenomena, where the electron-field interaction is modified by cross correlations with the rest of the interacting electrons, back reaction is a mechanism of autocorrelation. Our numerical simulations reveal back reaction as a relevant aspect in HHG from correlated two-electron systems, and paves the way to disentangle valence electron-electron correlation dynamics using high-harmonic spectroscopy., We acknowledge fruitful discussions with Tenio Popmintchev. We also acknowledge support from Junta de Castilla y León FEDER funds (Project No. SA287P18) and Ministerio de Ciencia e Innovación (FIS2016-75652-P and PID2019-106910GB-I00). C.H.-G. acknowledges Ministerio de Ciencia, Innovación, y Universidades for a Ramón y Cajal contract (RYC-2017-22745), co-funded by the European Social Fund. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 851201).

[ES]Durante las últimas dos décadas, el avance en el campo de los láseres ultraintensos y ultracortos ha mejorado nuestra comprensión de la materia sometida a campos láser intensos. A diferencia de otros campos no perturbativos de la física, la disponibilidad de la tecnología de láseres intensos en laboratorios de tamaño medio a nivel mundial ha proporcionado una fructífera interacción entre la teoría y los experimentos. Esta tesis es un ejemplo de esta interacción.La radiación electromagnética intensa induce una fuerte respuesta no lineal en la materia. Los electrones atómicos adquieren energía del campo láser, que puede ser posteriormente liberada en forma de radiación coherente de alta frecuencia, en un proceso conocido como generación de armónicos de orden elevado (HHG, procedente de sus siglas en inglés). La ausencia de láseres convencionales a estas frecuencias elevadas ha impulsado el interés tecnológico en el desarrollo de HHG como herramienta para conseguir fuentes coherente de luz de longitud de onda corta. Hasta hace muy poco, la tecnología de láseres ultraintensos se limitaba a longitudes de onda del infrarrojo cercano (alrededor de 800 nm) y la conversión en armónicos de orden elevado se limitaba a la región del ultravioleta lejano (XUV). Actualmente, con la mejoría de las técnicas de inversión paramétrica, este límite se encuentra en los rayos X blandos. Sin embargo, desde el inicio se reconocieron las aplicaciones potenciales del proceso HHG, más allá de las naturales de una radiación coherente de alta frecuencia. El espectro de HHG consiste en un peine de armónicos que se extienden hasta la denominada frecuencia de corte. En la región espectral cercana a este corte, los armónicos tienen intensidades similares y, lo que es más interesante aún, su distribución de fase espectral es suave. Con estas dos premisas, tras filtrar el espectro de baja frecuencia, la radiación resultante se corresponde a un tren de pulsos ultracortos en la región XUV, con duraciones en torno a unos cuantos centenares de attosegundos (1 attosegundo = 10-18 segundos), espaciadas regularmente cada medio ciclo del láser incidente. Tras su confirmación experimental a comienzos del siglo XXI, éstos son considerados los pulsos de luz coherente más cortos jamás creados. Esta tecnología está dando sus primeros frutos, pues ya se han identificado distintas aplicaciones para discriminar procesos ultrarrápidos (en el régimen de los attosegundos) en la dinámica de sistemas físicos, químicos y biológicos.El objetivo de esta tesis es realizar una contribución novedosa y original en este campo. El núcleo principal de este estudio consiste en el desarrollo de métodos teóricos para simular los experimentos. Esta estrategia contiene una vertiente doble. En primer lugar, la teoría se utiliza para comprender los resultados obtenidos experimentalmente. Para ello hemos desarrollado nuestros propios experimentos, que contrastamos directamente con los resultados teóricos y, además, hemos colaborado con dos grupos experimentales a nivel internacional con el objetivo de simular sus experimentos. En segundo lugar, hemos aplicado nuestra teoría para predecir nuevos procesos físicos y, de este modo servir de guía para la realización de nuevos experimentos. El punto de partida de esta tesis se basa en la teoría SFA+, desarrollada previamente en el área de óptica de la Universidad de Salamanca, para el cálculo del proceso de generación de armónicos de orden elevado en un solo átomo, a nivel microscópico. Este método, así como una extensa introducción al proceso HHG, se expone a lo largo del capítulo 1. Nuestro primer objetivo ha sido desarrollar un esquema de propagación de los armónicos de orden elevado que permite la simulación del proceso a escala macroscópica, de manera que la teoría sea comparable a los experimentos. Para ello, hemos implementado una nueva técnica de propagación basada en la aproximación dipolar discreta. Esta técnica, así como los fundamentos para la comprensión de la propagación de armónicos de orden elevado, se desarrollan en el capítulo 2.En el capítulo 3 estudiamos la propagación de armónicos de orden elevado generados por campos láser de longitud de onda en el infrarrojo cercano, focalizados en chorros o celdas de gas de baja densidad. Como primer test, hemos analizado teórica y experimentalmente el cambio en las condiciones de ajuste de fases que resulta de situar el chorro de gas en distintas posiciones a lo largo del eje de propagación. Una vez validado nuestro método teórico experimentalmente, proponemos una alternativa para acortar los pulsos de attosegundo, mediante su detección bajo distintos ángulos desde el eje de propagación. Posteriormente presentamos un estudio de la longitud de coherencia transversal, comparando nuestros resultados teóricos y experimentales. Finalmente, hemos implementado la geometría de una celda de gas semi-infinita en nuestro código de propagación, con el objetivo de comprender los resultados experimentales obtenidos por el grupo de M. Kovacev, en la Universidad de Hannover (Alemania). En el capítulo 4 hemos modificado nuestro método para estudiar la generación armónicos de orden ultra-elevado, producidos utilizando láseres de longitud de onda en el infrarrojo medio (aproximadamente de 4 µm), en colaboración con el grupo teórico de A. Becker y A. Jaron-Becker, del JILA, en la Universidad de Colorado (EEUU). El resultado principal de este trabajo consiste en la demostración de la coherencia temporal de los rayos X con energía de kiloelectronvoltio obtenidos en el grupo experimental de M. Murnane y H. Kapteyn en el JILA, Universidad de Colorado (EEUU), que lideró una colaboración internacional en la que también participaron la Universidad Técnica de Viena (Austria), la Universidad de Cornell (EEUU) y nuestro grupo. Como continuación a este trabajo, y gracias al desarrollo de nuestros métodos teóricos, hemos derivado un camino para obtener pulsos de luz de rayos X en el régimen de los zeptosegundos (1 zeptosegundo=10-21 segundos)., [EN]During the past two decades, progress in the field of ultra-intense and ultra-short lasers has improved our understanding of the subject under intense laser fields. Unlike other nonperturbative fields of physics, the availability of intense laser technology in medium-sized laboratories worldwide has provided a fruitful interaction between theory and experiment. This thesis is an example of this interaction.Intense electromagnetic radiation induces a strong nonlinear response in the subject. The atomic electrons gain energy from the laser field, which can be subsequently released as high-frequency coherent radiation, a process known as generation of high order harmonics (HHG, from its acronym in English). Conventional lasers absence of these higher frequencies has fueled interest in developing technology as a tool for HHG coherent light sources of short wavelength. Until recently, ultra-intense laser technology was limited to wavelengths of near infrared (around 800 nm) and conversion into higher-order harmonics was limited to the far-ultraviolet region (XUV). Currently, with the improvement of the parametric inversion techniques, this limit is in soft X-rays.However, from the beginning recognized the potential applications of HHG process, beyond a natural high frequency coherent radiation. HHG spectrum consists of a comb of harmonics which extend to the so-called cutoff frequency. In the spectral region near this cut harmonics have similar intensities and, even more interestingly, the spectral phase distribution is smooth. With these two assumptions, after filtering the low frequency spectrum, the resulting radiation corresponds to a train of ultrashort pulses in the XUV region, lasting about a few hundred attoseconds (1 attosecond = 10-18 sec), spaced regularly every half cycle of the laser incident. Following early experimental confirmation of the century, they are considered coherent light pulses shorter ever created. This technology is starting to pay off, as already identified different applications for discriminating ultrafast processes (in the attosecond regime) in the dynamics of physical systems, chemical and biological.The aim of this thesis is to make a new and original contribution in this field. The core of this study is the development of theoretical methods to simulate the experiments. This strategy contains a double aspect. First, the theory used to understand the results obtained experimentally. We have developed our own experiments, we contrast directly with the theoretical results and also we have worked with two experimental groups at the international level in order to simulate their experiments. Second, we have applied our theory to predict new physical processes and thus serve as a guide for conducting new experiments.The starting point of this thesis is based on the theory SFA +, previously developed in the area of ​​optics at the University of Salamanca, for calculating the process of generating high order harmonics in a single atom, a microscopic level. This method, as well as an extensive introduction to the HHG process, is exposed along the chapter 1. Our first objective was to develop a propagation scheme of higher order harmonics which allows the simulation of the process on a macroscopic scale, so that the theory is comparable to the experiments. To do this, we implemented a new propagation technique based on the discrete dipole approximation. This technique, as well as the basics for understanding the propagation of high-order harmonics, are developed in chapter 2.In Chapter 3, studied the propagation of a high order harmonic fields generated by laser wavelength in the near infrared, targeted cells jets or low density gas. As a first test, we analyzed theoretically and experimentally the change in conditions of phase adjustment that results from positioning the gas stream at various positions along the axis of propagation. Once experimentally validated our theoretical method, we propose an alternative to shorten attosecond pulses, by detecting different angles from the axis of propagation. We then present a study of the transverse coherence length, comparing our theoretical and experimental results. Finally, we implemented the cell geometry of a semi-infinite gas in our propagation code, in order to understand the experimental results obtained by the group of M. Kovacev, University of Hannover (Germany).In Chapter 4 we have modified our method to study the harmonics generation ultra-high, produced using wavelength lasers in the mid-infrared (approximately 4 microns), in collaboration with the theoretical group A. Becker and A. Jaron-Becker, of JILA, University of Colorado (USA). The main result of this paper is the demonstration of the temporal coherence of X-rays with energy kiloelectronvoltio obtained in the experimental group M. Murnane and H. Kapteyn at JILA, University of Colorado (USA), who led an international collaboration which also included the Technical University of Vienna (Austria), Cornell University (USA) and our group. Further to this work, and thanks to the development of our theoretical methods, we have derived a way to obtain light pulses in the X-ray regime zeptosegundos (1 zeptosegundo = 10 to 21 seconds).

Twisted light fields carrying orbital angular momentum (OAM) provide powerful capabilities for applications in optical communications, microscopy, quantum optics and microparticle rotation. Here we introduce and experimentally validate a new class of light beams, whose unique property is associated with a temporal OAM variation along a pulse: the self-torque of light. Self-torque is a phenomenon that can arise from matter-field interactions in electrodynamics and general relativity, but to date, there has been no optical analog. In particular, the self-torque of light is an inherent property, which is distinguished from the mechanical torque exerted by OAM beams when interacting with physical systems. We demonstrate that self-torqued beams in the extreme-ultraviolet (EUV) naturally arise as a necessary consequence of angular momentum conservation in non-perturbative high-order harmonic generation when driven by time-delayed pulses with different OAM. In addition, the time-dependent OAM naturally induces an azimuthal frequency chirp, which provides a signature for monitoring the self-torque of high-harmonic EUV beams. Such self-torqued EUV beams can serve as unique tools for imaging magnetic and topological excitations, for launching selective excitation of quantum matter, and for manipulating molecules and nanostructures on unprecedented time and length scales., Comment: 24 pages, 4 figures

Memoria ID-120. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2018-2019.

Resumen basado en el de la publicación Título, resumen y palabras clave en español y en inglés Se muestra cómo el fracaso escolar y el abandono escolar temprano, se han convertido en una preocupación de dimensiones internacionales que afecta a los sistemas educativos de todos los países. Las muestras, compuestas por 856 escolares de tercero y cuarto de la ESO con edades comprendidas entre los 15 y 16 años y otra de 748 padres. A lo largo de diferentes apartados, se analiza la evolución del fracaso y del abandono escolar prematuro en España, realizando una comparativa con los países de su entorno. También, se hace referencia a los distintos factores que influyen sobre los malos rendimientos académicos, distinguiendo entre factores internos y externos al sistema educativo. ESP

Memoria ID-0250. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2015-2016.

Memoria ID-0089. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2015-2016.

[EN][The visualization of collagen-based tissues imaged with second harmonic generation (SHG) microscopy strongly depends on the polarization state of the scanning laser beam. This has been often explored using spatially homogeneous states (mainly linear or circular). However, vector beams (i.e. laser beams with spatially non-uniform polarization states) have become a powerful tool in different research field and technological applications. In particular, radially polarized vector beams are known to provide a tight focal spot and lateral resolution enhancement. Here we propose the use of radially polarized beams to improve the quality of SHG microscopy images. The performance of this particular type of vector beam is compared to that obtained with a circularly polarized light beam for different non-stained specimens and depth locations. Results show that independently of the sample’s thickness, the efficiency of SHG processes is increased when using the radially polarized beam, also leading to a higher image quality. Our results open the route for using vector beams to get a better visualization of biological details within the imaged areas, especially at deeper locations., This work was supported by Ministerio de Ciencia e Innovación, Spain, Agencia Estatal de Investigación to J. M. B. (PID2020-113919RB-I00). R. M. O. was granted by a fellowship from Agencia Estatal de Investigación, Spain (BES-2017-081691). C.H-.G. acknowledges support from Ministerio de Ciencia e Innovación, y Universidades, Spain for a Ramón y Cajal contract (RYC-2017-22745), and the European Research Council (ERC) under Grant Agreement No. 851201.

Trabajo de fin de Grado. Grado en Física. Curso académico 20---20, [ES]Los haces de luz pueden presentar una rotación conforme se desplazan por el espacio. Esta rotación está asociada al momento angular, uno de cuyos tipos es el momento angular orbital (OAM). Los haces portadores de OAM se denominan "vórtices ópticos" o "haces helicoidales" por la característica forma de su perfil de fase e intensidad. La fase de un vórtice óptico sigue una distribución azimutal en torno al centro del haz, donde hay una singularidad de fase y, por tanto, un cero de la intensidad. Por su parte, los frentes de onda forman hélices a lo largo de su propagación por el espacio, siguiendo la distribución de la fase. El parámetro l, denominado carga topológica, está directamente relacionado con el valor de OAM y con el número de "vueltas" que la fase da en torno al origen a lo largo de la coordenada azimutal. La carga topológica es un número entero. Este amplio espacio de cargas topológicas hace al momento angular orbital muy interesante para ciertas aplicaciones. El objetivo de este trabajo es exponer diversas técnicas para caracterizar los haces con OAM en distintos rangos de frecuencias., [EN]Light beams can display a rotation as they move through space. This rotation is associated to angular momentum, one type of which is the orbital angular momentum (OAM). OAM-carrying beams are called "optical vortices" or "helical beams" due to the characteristic shape of their phase and intensity profile. The phase of an optical vortex follows an azimutal distribution around the beam centre, where a phase singularity is located and, as a consequence, an intesity of zero appears. As for the phase fronts, they form an helix as they propagate through space, following the phase distribution. The parameter l, named topological charge, is directly related to the OAM value and the number of times that the phase "rotates" around the origin along the azimutal coordinate. The topological charge is a whole number. This wide space of topological charge makes the orbital angular momentum very interesting for certain applications. The aim of this work is to showcase techniques for the characterisation of OAM beams in different frequency ranges.

Trabajo de fin de Grado. Grado en Física. Curso académico 2018-2019, [ES]En el año 2010, un grupo de científicos brasileños publicó un artículo donde mostraban como los patrones de difracción de una apertura triangular podían ser útiles para visualizar el momento angular orbital del haz difractado. Este artículo se centraba en el estudio de haces de luz con un frente de ondas helicoidal, es decir, ondas que se propagaban con la forma de un sacacorchos. En este trabajo, implementamos un modelo teórico que nos permite simular estos haces y, estudiar cómo se comportan al difractarse en la región de Fraunhofer por diferentes aperturas para poder caracterizar su momento angular orbital. Probaremos diferentes tamaños y tipos de aperturas para ver cuál es el método más óptimo para esta caracterización, así como estudiaremos los límites de ese procedimiento. Finalmente indagaremos en cómo funciona esta técnica para diferentes zonas del espectro electromagnético (diferentes longitudes de onda)., [EN]In 2010, a group of Brazilian scientists published an paper showing how diffraction patterns of a triangular aperture could be useful to visualize the orbital angular momentum of the diffracted beam. This paper focused on the study of light beams with a helical wave front, i.e. waves that propagate in the shape of a corkscrew. In this work, we implemented a theoretical model that allows us the simulation of these beams and the study of how they behave when diffracted in the Fraunhofer region through different openings, in order to characterize their orbital angular momentum. We will test different sizes and types of apertures in order to determine which is the most optimal method for this characterization, as well as to explore the limits of this procedure. Finally we will investigate how this technique works for different zones of the electromagnetic spectrum (different wavelengths).