Marina Fernández Galán from the Laser and Photonics Applications Group and the LUMES Excellence Unit at the University of Salamanca will give a seminar titled “Colliding Pulses: A Route to Generating Ultrashort Pulses in the Ultraviolet” on February 21 at 1:00 PM.
The seminar will take place in Room V of the Trilingual Building at the University of Salamanca.
Víctor W. Segundo Staels from the Laser and Photonics Applications Group and the LUMES Excellence Unit at the University of Salamanca will give a seminar titled ‘Understanding the Space-Spectral Homogeneity in Multipass Cells’ on February 11 at 1:00 PM.
The seminar will take place in Room III of the Trilingual Building at the University of Salamanca.
Sandra Gómez, from the Department of Chemistry at the Autonomous University of Madrid, will deliver the seminar titled “Quantum dynamics of excited states in simplified graphene systems” on February 4 at 12:00.
The seminar will take place in Room VII of the Trilingual Building at the University of Salamanca.
Marcos García Barriopedro, from the Complex Systems group at the Polytechnic University of Madrid, will deliver the seminar titled “Quantum Zeno effect and Zeno dynamics: application to particle teleportation and its optical implementation” on December 5 at 12:00.
The seminar will take place in Room IV of the Trilingual Building at the University of Salamanca.
This talk is part of the visit of Marcos García-Barriopedro, Isabel Gonzalo, and Miguel Ángel Porras within the framework of the FASLIGHT network (Fundamental and Applications of Structured Light), a Spanish network dedicated to the study of structured light.
FASLIGHT (RED2022-134391-T) is supported by the Ministry of Science and Innovation and the State Research Agency (MCIN/AEI / 10.13039/501100011033).
Elsa Abreu, from the Quantum Material Dynamics Institute for Quantum Electronics at ETH Zurich, will deliver the seminar titled “THz dynamics of quantum materials, also under pressure” on November 29 at 12:00.
The seminar will take place in Room IV of the Trilingual Building at the University of Salamanca.
Yago Radziunas Salinas, from the Photonics4Life group of the Department of Applied Physics at the University of Santiago de Compostela, will deliver the seminar titled “Laser structuring of devices for biological applications” on November 28 at 10:00.
The seminar will take place in the seminar room of the Laboratories in the Trilingual Building at the University of Salamanca.
This talk is part of the visit of Yago Radziunas Salinas and María Teresa Flores Arias within the framework of the FASLIGHT network (Fundamental and Applications of Structured Light), a Spanish network dedicated to the study of structured light.
FASLIGHT (RED2022-134391-T) is supported by the Ministry of Science and Innovation and the State Research Agency (MCIN/AEI / 10.13039/501100011033).
In this paper, published in collaboration with researchers from the Politecnico di Milano, ETH Zürich, and Lund University, we explore an innovative approach to generate isolated attosecond pulses using a semi-infinite gas cell. Traditionally, experiments generating these extremely short pulses employ gas jets or short gas cells at high pressures, ensuring the necessary phase matching for efficient high-order harmonic generation. However, longer, lower-pressure media have not been used due to the difficulties in achieving good phase matching over such a long distance, often leading to less effective results.
Our work challenges this conventional view by demonstrating that it is possible to efficiently generate isolated attosecond pulses in an extended medium configuration, such as a semi-infinite gas cell (SIGC) filled with a noble gas at low pressure. Our results show that the incident infrared field, during its nonlinear propagation through the SIGC, creates a plasma channel in the final part that plays a crucial role in self-regulating its spatiotemporal structure and facilitating the phase matching conditions necessary to produce these isolated attosecond pulses.
Experiments, conducted by our collaborators at the Politecnico di Milano, have managed to characterize, for the first time and clearly in an extended medium, isolated pulses with a duration of 180 attoseconds and a continuous spectrum in the 20-45 eV energy range, making them very useful for ultrafast spectroscopy experiments.
Supporting the experiments, we present detailed simulations developed by our team that provide a better understanding of the mechanisms involved. These simulations, which combine the atomic-level quantum dynamics of the harmonic generation process with the nonlinear propagation of the incident laser pulse, confirm the experimental findings. One of the most important aspects we observe is that the gradual increase in gas pressure in the cell creates a temporal window of phase matching during which the emission of attosecond pulses is especially efficient. As the pressure increases, this window is reduced, allowing the generation of a single attosecond pulse in half a cycle of the incident laser.
In summary, our work demonstrates that long media configurations, such as the semi-infinite gas cell, are not only viable for generating isolated attosecond pulses but, under the right conditions, can overcome some of the traditional limitations of short media, opening up new possibilities for experiments requiring extremely high temporal resolution. This advance could have applications in fields such as ultrafast spectroscopy and studies of electronic dynamics in complex materials.
More information in:
Vismarra, M. F. Galán, D. Mocci, L. Colaizzi, V. W. Segundo, R. Boyero-García, J. Serrano, E. C. Jarque, M. Pini, L. Mai, Y. Wu, H. J. Wörner, E. Appi, C. L. Arnold, M. Reduzzi, M. Lucchini, J. San Roman, M. Nisoli, C. Hernández-García, and R. Borrego-Varillas, “Isolated attosecond pulse generation in a semi-infinite gas cell driven by time-gated phase matching,” Light Sci. Appl. 13, 197 (2024). https://doi.org/10.1038/s41377-024-01564-5
In this work, we explore a novel theoretical approach to enhance our understanding of ultrashort laser pulse compression in gas-filled hollow-core fibers. These pulses are essential in ultrafast science, where they are used to study atomic and molecular dynamics on extremely short timescales. However, compressing these pulses to very short durations without the appearance of relevant secondary structures (pre-pulses and/or post-pulses) is a significant technical challenge. To address this challenge, we apply a method called “reverse nonlinear propagation,” which allows us to predict the ideal shape of the input pulse to achieve an optimal compressed pulse at the output. The key to this approach is that, instead of directly designing the input pulse, we simulate what an ideal pulse would look like at the output and reverse its propagation in the fiber to determine the characteristics the initial pulse should have.
The process of pulse compression typically involves using a hollow capillary filled with gas in which a laser pulse is coupled to broaden its spectrum during propagation, mainly due to self-phase modulation, a nonlinear effect that generates new frequencies very efficiently. Then, the phase of the new spectrum obtained at the output of the capillary is adjusted in an external compressor, composed of dispersive elements, to shorten the temporal duration of the pulse. The problem is that compressed pulses often exhibit undesired secondary structures, such as additional peaks that distort the pulse shape. Our method allows us to design an input pulse that minimizes or eliminates these secondary structures.
One of the most interesting findings is that the ideal pulse predicted by the reverse propagation technique has a characteristic profile: its spectrum always presents small modulations around the main peak. Our simulations demonstrate that these initial spectral modulations allow compensating for the nonlinear effects that occur inside the capillary during the pulse propagation to produce the clean pulse at the output.
The reverse propagation method is not new, but its application in this context presents particular challenges due to the high energy losses of hollow-core fibers and the symmetries of the equation that describes the nonlinear propagation of ultrashort pulses. Despite these complications, we demonstrate that it is possible to numerically reverse the pulse propagation and accurately predict the characteristics of the input pulse required to obtain optimal compression.
Furthermore, our study highlights the high sensitivity of the compression process to small changes in the phase and amplitude profile of the input pulse. Even slight variations in the initial phase or amplitude can lead to significantly different results at the output, underlining the importance of controlling both aspects in the design of experiments.
In summary, this work proposes a new theoretical tool that can guide the design of ultrashort pulse compression experiments in laboratories. While some of our results still need to be experimentally validated, we believe that this method opens the door to generating clean and ultrashort pulses that could improve applications in ultrafast spectroscopy, strong-field physics, and other areas of ultrafast science.
More information in:
F. Galán, E. C. Jarque, and J. San Roman, “Reverse design of the ideal pulse for hollow capillary fiber post-compression schemes,” Phys. Rev. Res. 6(2), 023111 (2024). https://doi.org/10.1103/PhysRevResearch.6.023111
Gonçalo Figueira from the Department of Physics & GoLP/IPFN at Instituto Superior Técnico in Lisbon (Portugal) will deliver a seminar titled “Ultrafast Laser Research at IST Lisbon” on October 24 at 1:00 p.m.
The seminar will take place in Room V of the Edificio Trilingüe at the University of Salamanca.
The seminar will take place in Classroom V of the Edificio Trilingüe at the University of Salamanca
