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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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OP Session – Novel ultrafast sources for attosecond spectroscopy

Rocío Borrego Varillas from the Institute of Photonics and Nanotechnology at the National Research Council will give a seminar titled “Novel ultrafast sources for attosecond spectroscopy” on June 11th at 12:30 PM.

The seminar will take place in Room VII of the Trilingual Building at the University of Salamanca.

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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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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

2×1 in ultrashort laser pulses

In the last decades, ultrashort laser pulses have revolutionized our way of studying the microscopic world through the interaction of coherent light with matter. The generation and manipulation of these ephemeral electromagnetic fields allows us to access the fastest atomic phenomena in nature, occurring on the femto to attosecond (10-15-10-18 s) time scale. The rapid advancement of laser technology has made it possible, in recent years, to synthesize infrared pulses with sub-cycle durations, in which the most intense structure of the electric field of light barely has time to complete an oscillation at its central frequency. These pulses provide a unique tool for exploring electron motion in atoms and molecules, but their generation is still limited to extremely expensive and complex setups.

Recently, we demonstrated that these sub-cycle pulses can be obtained much more simply in standard systems based on the propagation of light through gas-filled hollow capillary fibers with a decreasing pressure gradient. This proposal is based on a surprising phenomenon of nonlinear optics, known as soliton self-compression, where an intense laser pulse can, by itself, simultaneously broaden and organize its frequency spectrum, reducing its duration almost to the limit. By following some scaling rules to design the fiber and input pulse parameters, this technique allows for the generation of high quality sub-cycle infrared pulses.

Not content with reaching durations of just one femtosecond, in our latest work, conducted in collaboration with researchers from Politecnico di Milano and Heriot-Watt University, we have explored the application of these sub-cycle fields to generate even shorter laser pulses in the attosecond regime. To do so, we have exploited the phenomenon of high-order harmonic generation, which arises from the interaction of an intense infrared pulse with the atoms of a gas. When the interaction is performed with a conventional laser, this process works as a production chain of attosecond pulses in the extreme ultraviolet, giving rise to a series of light flashes that occur at regular time intervals. However, if the interaction is driven by one of our previous sub-cycle pulses, the harmonic generation process is naturally confined to a single event, resulting in the direct emission of an isolated attosecond pulse. These solitary ultraviolet pulses are a highly sought-after tool in ultrafast science applications where very precise control and high temporal resolution are needed.

Thus, our study opens the door to a new generation of compact fiber-based systems in which, starting from a standard infrared laser pulse, we combine for the first time its extreme self-compression down to the sub-cycle regime and its direct application to generate extreme-ultraviolet isolated attosecond pulses.

More information in:

  1. F. Galán, J. Serrano, E. C. Jarque, R. Borrego-Varillas, M. Lucchini, M. Reduzzi, M. Nisoli, C. Brahms, J. C. Travers, C. Hernández-García, and J. San Roman, “Robust isolated attosecond pulse generation with self-compressed sub-cycle drivers from hollow capillary fibers,” ACS Photonics 11(4), 1673-1683 (2024).

https://doi.org/10.1021/acsphotonics.3c01897

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VI Photographic Contest “DAY OF LIGHT”

On the occasion of the proclamation of May 16 as the “International Day of Light and Light-Based Technologies” by the United Nations, the University Master’s Degree in Physics and Laser Technology announces the VI edition of the “Day of Light” Photographic Contest.

In the organization of the contest and the formation of the jury participate:

The contest is open to undergraduate, master’s, or doctoral students, faculty, and members of the university community of the University of Salamanca and the University of Valladolid, as well as graduates of the Master’s Degree in Physics and Laser Technology who are not part of the jury.

The participation period is open until May 31st. Each participant can submit up to two photographs for each of the established categories:

  1. Light Technologies and Optical Phenomena.
  2. The Laser.

Four prizes will be awarded:

  • First prize in the category of Light Technologies and Optical Phenomena: 200 euros.
  • Second prize in the category of Light Technologies and Optical Phenomena: 100 euros.
  • First prize in the category of The Laser: 200 euros.
  • Second prize in the category of The Laser: 100 euros.

In addition, those winners who are undergraduate, master’s, or doctoral students will receive a one-year free subscription to the Royal Spanish Society of Physics with online access to the Physics Journal. The awarded photographs will be published in the journal “Optica Pura y Aplicada” of the Spanish Society of Optics (SEDOPTICA).

The complete rules of the contest are available on the website of the Master’s Degree in Physics and Laser Technology (laser.usal.es/posgrado).

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adminVI Photographic Contest “DAY OF LIGHT”

Researchers from the Institute of Ion Beam Physics and Materials Research visited ALF-USAL

Researchers Rang Li and Chi Pang, from the Institute of Ion Beam Physics and Materials Research (Helmholtz-Zentrum Dresden-Rossendorf), conducted an experimentation campaign last week at the USAL Laser Laboratory.

These researchers are working on the development of new advanced materials for photonics applications such as nanomembrane microcavities.

They utilize various experimental devices based on ultrashort pulse lasers developed by the researchers of the ALF group, Carolina Romero, Ignacio López, Íñigo Sola, and Javier Rodríguez.

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adminResearchers from the Institute of Ion Beam Physics and Materials Research visited ALF-USAL

The President of the Junta of Castilla y León meets with researchers from the European Research Council program.

On Monday, March 18th, the President of the Junta of Castilla y León, Alfonso Fernández Mañueco, held a meeting with seven out of the nine researchers from the region selected in the European Research Council (ERC) program, among whom is Carlos Hernández García, a member of the ALF Group – USAL and principal investigator of the Attostructura project.

The news has been widely disseminated by several media outlets, which have issued press releases regarding the matter.

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adminThe President of the Junta of Castilla y León meets with researchers from the European Research Council program.