Scientific outreach


We are pleased to announce the defense of the doctoral thesis of Ana García Cabrera, titled “Efectos de las simetrías del cristal en la generación de armónicos altos en grafeno.” The defense will take place on Monday, July 29th, at 11:00 in Aula III of the Edificio Trilingüe. The thesis directors are Dr. Luis Plaja Rustein and Dr. Carlos Hernández García.

We cordially invite you to attend this important presentation, as your presence and support will be greatly appreciated.

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Visit and Collaboration of Ming-Chang Chen with the ALF Group at the University of Salamanca

We are delighted to announce that Ming-Chang Chen from the National Tsing Hua University in Hsinchu, Taiwan, visited the Laser Applications Group at the University of Salamanca (USAL) from July 8th to July 10th, 2024. During his visit, in addition to holding meetings with the group’s researchers and touring the laboratory, he delivered a lecture on July 10th titled “Advancements in Turn-Key Attosecond Light Sources and Their Application in Probing Spin Dynamics.”

The collaboration between Ming-Chang Chen and the ALF group has a long history, dating back to 2016. As a result of this collaboration, several research articles have been published, thereby strengthening the bond between both institutions and significantly advancing the field of laser technology.

  1. Chang, K.-Y., Huang, L.-C., Asaga, K., Tsai, M.-S., Rego, L., Huang, P.-C., Mashiko, H., Oguri, K., Hernández-García, C., & Chen, M.-C. (2021). High-order Nonlinear Dipole Response Characterized by Extreme-Ultraviolet Ellipsometry. Optica, 8, 484-492.
  2. Chang, K.-Y., Huang, L.-C., Asaga, K., Tsai, M.-S., Rego, L., Huang, P.-C., Mashiko, H., Oguri, K., Hernández-García, C., & Chen, M.-C. (2021). High-order Nonlinear Dipole Response Characterized by Extreme-Ultraviolet Ellipsometry. Optica, 8, 484-492.
  3. P. -C. Huang, C. Hernández-García, J. -T. Huang, P. -Y. Huang, L. Rego, C. -H. Lu, S. -D. Yang, L. Plaja, A. H. Kung, & M. -C. Chen. (2019). Realization of Polarization Control in High-Order Harmonic Generation. IEEE Journal of Selected Topics in Quantum Electronics, 25(4), 1-12.

Prof. Chen established the ATTO-EUV lab in 2013 with the goal of generating bright and coherent EUV lasers on a tabletop. His recent research is dedicated to advancing laser technology and producing the shortest and brightest high-order harmonic EUV source. Notably, he pioneered and demonstrated the complete solution for controlling the polarization of isolated attosecond pulses and invented the broadband EUV polarimeter. By introducing the highly efficient post-compression technique, CASCADE, he enabled the production of single-cycle IR pulses and isolated attosecond EUV pulses. This accessible and reliable tabletop EUV light source has opened up numerous possibilities, including pioneering EUV spectroscopic ellipsometry and achieving the brightest EUV light source for nano-imaging.

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adminVisit and Collaboration of Ming-Chang Chen with the ALF Group at the University of Salamanca

Participation of the ALF USAL Group in RNO2024

The ALF USAL group had a prominent participation in the XIV National Optics Meeting and the V National Young Optics Meeting (RNO2024) held from July 2 to 5 in Murcia, Spain.

This event, which brings together leading experts and young talents in the field of optics, has been an exceptional platform to present the latest advances in research and development in this field.

The group contributed with a series of works that address various areas of modern optics, standing out for their innovation and scientific rigor. The presented works are summarized below:

  1. Attosecond Structured Light (Invited)
    Autor: Hernández García, C.
  2. Diseño de guías de ondas superficiales optimizadas para sensado y extracción de luz en materiales cristalinos fabricadas mediante escritura directa con láser de femtosegundo (Oral)
    Autores: Arroyo Heras, V., López Quintas, I., Vázquez De Aldana, J. R., Bonduelle, M., Martín, G., & Romero Vázquez, C.
  3. Medida de pulsos ultracortos vectoriales con amplitude swing (Oral)
    Autores: Barbero, C., Alonso, B., & Sola Larrañaga, I. J.
  4. Towards an all-fiber source of isolated attosecond pulses driven by high-energy sub-cycle waveforms from soliton dynamics (Oral)
    Autores: Fernández Galán, M., Serrano, J., Conejero Jarque, E., Borrego-Varillas, R., Lucchini, M., Reduzzi, M., Nisoli, M., Brahms, C., Travers, J. C., Hernańdez-García, C., & San Román, J.
  5. Sistema óptico aplicado a la espectroscopía resuelta en tiempo en el rango de femtosegundo y picosegundo (Oral)
    Autores: Guerras, M., Lópe Quintás, I., & Sola Larrañaga, I. J.
  6. Intense and isolated polarization-controlled magnetic fields from structured laser beams to drive nonlinear magnetization dynamics (Oral)
    Autores: Martín Domene, S., Sánchez-Tejerina, L., Martín-Hernández, R., & Hernández García, C.
  7. Generation of extreme-ultraviolet high-topological charge spatiotemporal optical vortices (Oral)
    Autores: Martín-Hernández, R., Gui, G., Plaja, L., Kapteyn, H. C., Murnane, M. M., Liao, C.-T., Porras, M. Á., & Hernandez-Garcia, C.
  8. Self-interference of Hermite-Gaussian high-order harmonics simulated through machine learning (Oral)
    Autores: Pablos-Marín, J. M., Schmidt, D., De Las Heras, A., Westlake, N., Serrano, J., Lei, Y., Kazansky, P., Adams, D., Durfee, C., & Hernández García, C.
  9. Topological spectroscopy: High Harmonic Generation from Graphene irradiated by structured fields (Oral)
    Autores: Plaja, L., García Cabrera, A., Boyero-García, R., Zurrón-Cifuentes, O., Serrano, J., San Román, J., & Hernández-García, C.
  10. Improving pulse self-compression in photonic crystal fibers using particle swarm optimization algorithm. (Oral)
    Autores: Vaquero, A., Galán, M. F., Rodríguez Frías, M. D., Conejero Jarque, E., & Méndez, C.
  11. Macroscopic simulations of high-order harmonic generation assisted by artificial intelligence. (Oral)
    Autores: Serrano, J., Pablos-Marín, J. M., & Hernández García, C.
  12. Clean Temporal Pulses from All-Bulk Multipass Cells. (Oral)
    Autores: Segundo-Staels, V., Conejero Jarque, E., & San Roman, J. 
  13. Microscopía de generación de segundo armónico en cristales microestructurados con pulsos de femtosegundo: BBO y Nd:YAG. (Oral)
    Autores: Sevilla-Sierra, N., Rodríguez Vázquez de Aldana, J., Romero Vázquez, C., Mateos, X., & López Quintas, I.
  14. PW-class laser spatio-temporal characterization (Póster)
    Autores: Barbero, C., García-García, E., Mendez, C., Rodríguez Frias, M. D., López-Ripa, M., Sola Larrañaga, I. J., & Alonso Fernández, B.
  15. Fabricación de dispositivos fotónicos funcionales mediante escritura directa con láseres de femtosegundo. (Póster)
    Autores: Romero Vázquez, C., Arroyo Heras, V., Sevilla Sierra, N., López Quintás, I., & Vázquez De Aldana, J. R. 

In addition to presenting their work, the researchers from the ALF USAL group also contributed to the conference by moderating several oral communication sessions:

  • Luis Plaja, moderator of the Quantum and Nonlinear Optics session on Wednesday, July 3
  • Carlos Hernández García, moderator of the Quantum and Nonlinear Optics session on Thursday, July 4

These works reflect the ALF USAL group’s commitment to scientific excellence and their ability to lead in the field of optical research. The diversity and depth of their studies presented at RNO2024 underscore their crucial role in advancing modern optics.

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adminParticipation of the ALF USAL Group in RNO2024

Participation in the XVII National Congress on Materials CNMAT24

We are pleased to announce that three researchers from the Laser Applications and Photonics Group at the University of Salamanca have participated in the XVII Edition of the National Congress on Materials (CNMAT24). The congress took place from June 25 to 28, 2024, in the city of Málaga and brought together national and international experts in the field of materials.

Researchers Pablo Moreno Pedraz, Javier Rodríguez Vázquez de Aldana, and Ignacio López Quintás presented their latest work at this prestigious event, highlighting advancements and innovative applications in the field of photonics and laser technology.

  • Javier Rodríguez Vázquez de Aldana participated as the moderator of the Laser Material Processing symposium and also presented the poster titled “Microstructuring of transparent crystalline materials with ultrashort pulse lasers: new developments and applications.”
  • Pablo Moreno Pedraz presented the work titled “Influence of the substrate and thickness on the formation of LIPSS in thin polymer films.”
  • Ignacio López Quintás presented the work titled “Second harmonic generation in Nd crystals microstructured by laser.”

The participation of our researchers in CNMAT24 not only reinforces our group’s position at the forefront of scientific research but also demonstrates our continuous commitment to excellence and innovation in the field of photonics and laser technology.

Congratulations to Pablo, Javier, and Ignacio for their outstanding contribution and for representing our group and the University of Salamanca so well at this important event!

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adminParticipation in the XVII National Congress on Materials CNMAT24


Researchers Carlos Hernández García and Rodrigo Martín-Hernández, members of the Laser and Photonics Applications Group and the ERC Attostructura project (851201), actively participated in the Seventh International Conference on Optical Angular Momentum. This prestigious conference took place from June 10 to 13, 2024, at Kruger National Park, South Africa.

The Seventh International Conference on Optical Angular Momentum (ICOAM 2024) is a prominent event in the field of optics and photonics, focusing on the study and applications of light’s angular momentum. This event gathers scientists and experts from around the world to discuss the latest advancements and share innovative research in areas such as particle manipulation, quantum optics, generation of angular momentum beams, and biomedical and communication applications.

  • Carlos Hernández García participated as an invited speaker with his work titled “Attosecond vortex pulse trains”.

The landscape of ultrafast structured light pulses has recently evolved thanks to the capability of high-order harmonic generation (HHG) to nonlinearly convert orbital angular momentum (OAM) from infrared to extreme-ultraviolet/soft X-rays. Up to now, HHG has been demonstrated to produce harmonic vortex pulses on the femtosecond scale through various studies, where higher-order harmonics exhibit distinct OAM content. This characteristic, a result of OAM conservation rules, has hindered the emission of vortex beams with attosecond pulse durations.

In this work, we demonstrate, both theoretically and experimentally, the generation of attosecond vortex pulse trains – a succession of light pulses each with a temporal duration of hundreds of attoseconds, and a similar helical wavefront. This achievement is realized by synthesizing a comb of high-order harmonics with identical OAM. To our knowledge, these are the first vortex pulses produced on the attosecond scale.

To achieve this, we drove HHG with an infrared bifurcated polarization tilt-angle grating, resulting from the non-collinear superposition of two counter-rotating circularly polarized beams with opposite OAM. The simultaneous conservation of linear momentum, spin angular momentum, and orbital angular momentum in the HHG process leads to two spatially-separated circularly polarized high-order harmonic beams with OAM independent of the order. Our work paves the way towards attosecond-resolved light-matter interactions at the natural timescale of electronic dynamics in atoms, molecules, or solids.

  • Rodrigo Martín-Hernández participated in the poster session with the work titled “How to generate spatiotemporal optical vortices in the extreme-ultraviolet/x-ray regime.”

The generation of spatiotemporal optical vortices (STOVs) in the near-infrared regime has been successfully studied in recent years, both theoretically and experimentally. However, their extension to higher-frequency regimes has not yet been demonstrated. Over the last decade, it has been shown that high-order harmonic generation (HHG) can successfully transfer longitudinal optical vortices from the near-infrared to the extreme-ultraviolet (EUV) and X-ray regimes. Following an immediate analogy, one might think that HHG driven by STOVs would result in high-frequency STOVs with high topological charge. However, this scenario offers much richer possibilities.

In this work, we explore the nonlinear conversion of STOVs from the near-infrared to EUV/X-rays using HHG. Depending on the driving beam configuration, we identify two scenarios that lead to strongly differentiated phenomena.

Firstly, if HHG is driven by a canonical, elliptical, single-charged STOV focused on a gas target, high-frequency harmonic STOVs with the same topological charge as the driving field are generated. Our theoretical calculations unequivocally demonstrate that this result depends heavily on the non-perturbative nature of the HHG process. Thus, these results not only provide harmonic combs of low-topological charge STOVs in the EUV/X-ray range but also open the door to investigating some of the most fundamental questions about the intrinsic non-perturbative nature of the HHG process.

Secondly, if the driving beam is designed to deliver a canonical (elliptical), single-charged STOV at the gas target, high-order harmonic STOVs with high topological charge are generated. We demonstrate that in this scenario, the resulting topological charge of the harmonic STOVs increases according to the harmonic order multiplied by the fundamental topological charge, following the same well-known conversion rule as in longitudinal optical vortices.

Carlos Hernández García and Rodrigo Martín-Hernández’s participation in ICOAM 2024 underscores the Laser and Photonics Applications Group’s commitment to cutting-edge research and international collaboration in the field of optics and photonics. Their work not only contributes to the advancement of scientific knowledge but also opens new opportunities for innovative technological applications.

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ALF-USAL drives innovations in biomedical implants with MELTIO’s 3D technology.

The research group ALF-USAL from the University of Salamanca is participating in the ATILA project, which focuses on developing new applications for biomedical implants. This project, led by AIDIMME and also involving the FIHGUV foundation, uses MELTIO’s metal 3D printing technology.

ALF-USAL is responsible for initial studies on the parameters needed to create models simulating the additive manufacturing process. These studies are crucial for improving implant biocompatibility and customization.

The project faces challenges in material precision and adaptability but has made significant progress in creating personalized, biocompatible implants.

For more details, visit the COPE press release.

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adminALF-USAL drives innovations in biomedical implants with MELTIO’s 3D technology.

OP SESSION – Heat Transfer Mechanisms in Nanoscale Materials

Rosa Pilar Merchán Corral, a colleague from the Laser and Photonics Applications Group, will give a seminar titled “Heat Transfer Mechanisms in Nanoscale Materials” on June 17 at 12:30 PM.

The seminar will take place in classroom VI of the Trilingual Building at the University of Salamanca.

In this talk, a brief review of main heat equations will be presented, starting with the classical Fourier’s law and advancing into the Maxwell-Cattaneo-Vernotte and Guyer-Krumhansl equations. Furthermore, key heat conduction regimes (diffusive, hydrodynamic, ballistic) in nano-scale materials will be analysed. Finally, a possible experimental setup in semiconductors will be shown, along with some current studies and their key outcomes.

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adminOP SESSION – Heat Transfer Mechanisms in Nanoscale Materials

Isolated and intense polarization-controlled optical magnetic fields

Usually, when talking about laser-matter interaction, only the electric field associated with such electromagnetic radiation is taken into account. One of the reasons for this is that the excitations induced by the magnetic field are orders of magnitude smaller than those driven by the electric field. However, the interest in coherently probing magnetic systems on specific time and space scales, outside the scope of traditional magnetic field sources such as electromagnets, demonstrates the need to develop new schemes for the design and control of the electromagnetic field that forms light. This is possible thanks to the large structured light zoo, being able to manipulate different degrees of freedom such as intensity, phase or polarization state. Although there are several studies that address the separation of the magnetic field from the associated electric field in a light beam, in most cases it is necessary the interaction with matter to induce electrical currents for the creation of a sufficiently intense and isolated longitudinal linearly polarized magnetic field.

With our theoretical study we go one step further in this scenario, looking for a magnetic field whose polarization state can be controlled, ranging from linear to circular through elliptical. When such optical magnetic field with cylindrical symmetry along the beam propagation axis is introduced into Maxwell’s equations that govern classical electromagnetism, the result is an extremely complex associated electric field distribution. This consists of an optical vortex (a beam in which the phase or wavefront forms a helix as it propagates; this is known as the orbital angular momentum of light) with a single polarization component along the propagation axis. This challenging solution is beyond the current laser technology, so other more realistic schemes need to be adopted.

In our work we propose the coherent superposition of several dephased structured beams, in a way that only by their optical manipulation one can have direct control over the polarization state of the resulting isolated magnetic field in a given region of space. On one hand, we use azimuthally polarized vector beams as drivers to exploit their magnetic longitudinal component linearly polarized along the axis where the electric field is zero due to the polarization singularity. By tightly-focusing them with a large numerical aperture optical system outside the paraxial regime, this component can be confined and intensified starting from relatively low intensity lasers. By combining two or four of these focused beams in a cross geometry with the respective focus at the same point and applying the corresponding phase shifts, it is possible to achieve an intense magnetic field, isolated from the electric field and with circular polarization laying in the plane in which the driving beams are arranged, in a sub-wavelength region.

Our results obtained from a a feasible experimental setup point of view open the doors to new perspectives in such wide applications as optical and magnetic spectroscopy, force microscopy or ultrafast magnetization dynamics. In particular, the inspection of magnetic interactions with intense lasers in the ultrafast regime with phenomena such as the nonlinear dynamics of magnetization in ferromagnetic samples, the study of chiral materials or applications in the potential improvement of spatial resolution in the optical interaction with magnetic systems are particularly attractive.

More info at:

Sergio Martín-Domene, Luis Sánchez-Tejerina, Rodrigo Martín-Hernández, Carlos Hernández-García; Generation of intense, polarization-controlled magnetic fields with non-paraxial structured laser beams. Appl. Phys. Lett. 20 May 2024; 124 (21): 211101.

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adminIsolated and intense polarization-controlled optical magnetic fields

Announcement of defense of doctoral thesis – Alba de la Heras

On May 24th, Alba de las Heras Muñoz will present her doctoral thesis titled “Study of Multielectron Dynamics and Structured Laser Beams in Attosecond Physics” supervised by Dr. Carlos Hernández García and Dr. Luis Plaja Rustein.

The defense will take place at 11:00 AM in Room III of the Trilingual Building.

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adminAnnouncement of defense of doctoral thesis – Alba de la Heras

Attostructura participates in Pint of Science 24

Carlos Hernández García, the principal researcher of the Attostructura project, will be part of the exciting Pint of Science24 event. This international festival, held annually in bars, pubs, and other informal venues across multiple countries around the world, offers a unique experience where scientists and researchers share their knowledge in engaging and accessible talks for all audiences.

During Pint of Science, the exchange of ideas flows in a relaxed and social atmosphere, aiming to bring science closer to society and foster dialogue between experts and the general public.

Don’t miss Carlos’ participation on May 13th with his fascinating talk “Life in a Trillionth of a Second,” starting at 8:00 PM at Manolita (C/ Palominos 21). An unmissable opportunity to explore the mysteries of our universe in an informal and enjoyable setting!

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adminAttostructura participates in Pint of Science 24