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High fashion jewelry in non-linear optics

Sterling silver jewelry, rose gold with exclusive designs, rings, earrings, bracelets… made out of light? Like a high fashion jewelry workshop, the Laser and Photonics Applications research group of the University of Salamanca (ALF-USAL) focuses its efforts on designing light jewels through non-linear optics. Jewels, not only for their beauty in the form of high-frequency lasers, but also for their usefulness in observing and controlling unknown processes in nature. In fact, the design of coherent and high-frequency laser light beams (towards the X-rays) has become a unique tool to access processes that take place in very small sizes (nanometers) and in very short times (trillionths of seconds).

The theoretical-experimental collaboration between ALF-USAL and the group of Profs. Murnane and Kapteyn at the University of Colorado at Boulder (USA) have been developing fine jewelry for the last few years. After generating high-frequency rings with properties never seen before (see references [1,2]), the researchers have gone a step further, entering the world of necklaces. The design of an infrared laser in the form of a necklace allows to control the frequency and divergence (or spatial size) of the X-rays that are produced after the non-linear process of high-order harmonic generation. In this work, published in the journal Science Advances, the researchers also demonstrate that the spectral content of these X-ray lasers can be calibrated by means of the number of beads in the necklace. One more step in the high fashion jewelry with lasers that tries to help in the understanding of the fastest processes of nature.

More information in:

“Necklace-structured high harmonic generation for low-divergence, soft X-ray harmonic combs with tunable line spacing”, Laura Rego, Nathan J. Brooks, Quynh L. D. Nguyen, Julio San Román, Iona Binnie, Luis Plaja, Henry C. Kapteyn, Margaret M. Murnane, Carlos Hernández-García, Science Advances 8, eabj7380 (2022).

References::

[1] “Generation of extreme-ultraviolet beams with time-varying orbital angular momentum”, Laura Rego, Kevin M Dorney, Nathan J Brooks, Quynh Nguyen, Chen-Ting Liao, Julio San Román, David E Couch, Allison Liu, Emilio Pisanty, Maciej Lewenstein, Luis Plaja, Henry C Kapteyn, Margaret M Murnane, Carlos Hernández-García, Science 364, eaaw9486 (2019).

[2] “Controlling the polarization and vortex charge of attosecond high-harmonic beams via simultaneous spin-orbit momentum conservation”, Kevin M. Dorney, Laura Rego, Nathan J. Brooks, Julio San Román, Chen-Ting Liao, Jennifer L. Ellis, Dmitriy Zusin, Christian Gentry, Quynh L. Nguyen, Justin. M. Shaw, Antonio Picón, Luis Plaja, Henry C. Kapteyn, Margaret M. Murnane, Carlos Hernández-García, Nature Photonics 13, 123–130 (2019).

25 April, 2022 admin ALF results, Review No comments

OP Session – Applications of photo-registration laser for astrophotonics and spectrometry

Guillermo Martin, from the Institut de Planetologie et d’Astrophysique de Grenoble (FRANCE), will give the Seminar “Applications of photo-registration laser for astrophotonics and spectrometry“.

The seminar will take place on Tuesday, April 5 at 12:00 in E2 room in the Sciences School of the University of Salamanca

31 March, 2022 admin OP Session No comments

IV Photo Contest “Day of Light”

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

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

the ATTOSTRUCTURA project (funded by the European Innovation Council in the framework of the European Commission’s Horizon 2020 research program on innovation under the grant agreement ERC 851201).
the Salamanca Local Section of the Royal Spanish Society of Physics.
the Spanish Society of Optics SEDOPTICA.
the magazine Óptica Pura y Aplicada.
the University Association OSAL Student Chapter.
the Supernova University Association.
the Physics League University Association.

The contest is open to undergraduate, master’s or doctoral students, professors 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 Laser Physics and Technology who are not part of the jur

The participation period is open until May 3. Each participant can send up to two photographs to each of the established categories:

Technologies of light and Optical Phenomena
The laser

4 prizes will be awarded:

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

In addition, all the winners will receive one year of free subscription to the Royal Spanish Physics Society with online access to the Physics Journal. The winning photographs will be published in the Pure and Applied Optics magazine of the Spanish Optical Society (SEDOPTICA).

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

21 March, 2022 admin News, Scientific outreach No comments

Jila Press Release – A Necklace Made of Doughnuts

Our friends and frequent collaborators from JILA (University of Colorado) echo the paper “Necklace-structured high-harmonic generation for low-divergence, soft x-ray harmonic combs with tunable line spacing” recently published in ScienceAdvances.

You can read his review at the following link: https://jila.colorado.edu/news-events/articles/necklace-made-doughnuts

More information at:

Rego, L., Brooks, N. J., Nguyen, Q. L. D., San Roman, J., Binnie, I., Plaja, I., Kapteyn, H. C., Murnane, M. M., & Hernández-García, C. (2022). Necklace-structured high-harmonic generation for low-divergence, soft x-ray harmonic combs with tunable line spacing. Science Advances, 8(5), eabj7380. https://doi.org/10.1126/sciadv.abj7380

24 February, 2022 admin ALF results, Press release No comments

OP Session – How do Photons Combine in Non-perturbative Physics?

Matthieu Guer, a member of the École Nórmale Supérieure de Lyon who is doing a research stay in the Laser and Photonics Applications group (ALF – USAL), will give the seminar entitled “How do photons combine in non-perturbative physics?”.

The seminar will take place on Thursday, February 24 at 09:15 in Aula VII in the Trilingual Building of the University of Salamanca.

22 February, 2022 admin OP Session No comments

Compressing light pulses in pressure gradients

In spite of having an extremely short life, of just a few quadrillionths of a second, ultrashort femtosecond laser pulses have become an indispensable tool in many areas of science and technology, as they allow to probe the most fundamental properties of matter on ultrafast time scales.

Generating these such short pulses of light in a controlled manner and with a good quality is not an easy task, and in the last years various strategies have been proposed. The main idea is to generate a very wide light spectrum, made up of many frequencies, by means of nonlinear processes starting from a narrower one, and then correcting its phase to synchronize all the frequencies, giving rise to an ultrashort pulse. A widely used method to achieve this large spectral broadening is to propagate an initial light pulse through a hollow cylindrical fiber filled with a gas. In this case, one of the parameters that most influences the propagation is the pressure of the filling gas, which allows for a continuous tuning of the dispersion and the intensity of the nonlinear effects experienced by the pulse. In particular, if the fiber and gas parameters are carefully chosen, the incident pulse can broaden its spectrum while correcting its phase due to the interaction between the linear and nonlinear processes. In this way, the pulse reduces its duration on its own, in a process known as soliton self-compression.

Usually, these experiments are carried out keeping the gas at constant pressure, homogeneously filling the fiber. However, in one of our latest studies we have shown that applying a decreasing pressure gradient, causing the gas concentration to gradually decrease during propagation, can improve the quality of the self-compressed pulses and reduce their duration even more than constant pressure.

You can look up for all the details of this work at:

F. Galán, E. C. Jarque, and J. San Roman, Optimization of pulse self-compression in hollow capillary fibers using decreasing pressure gradients, Optics Express 30(5), 6755–6767 (2022). https://doi.org/10.1364/OE.451264

Download the full paper at Gredos @Universidad de Salamanca: http://hdl.handle.net/10366/148576

21 February, 2022 admin ALF results, Review No comments

PhD Student Position on Artificial Intelligence Applied to the Physics of Attosecond Laser Pulses

The University of Salamanca (Spain) invites application for a 3-year PhD Student position to obtain a PhD degree in Physics, starting in September 2022. The position is part of the project ATTOSTRUCTURA, “Structured attosecond pulses for ultrafast nanoscience”, funded by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement No. 851201), supervised by Dr. Carlos Hernández-García, and with a duration of 5 years.

Application deadline: May ^2nd 2022

Project information

The PhD candidate will enroll the project “Structured attosecond pulses for ultrafast nanoscience” at the Laser Applications and Photonics Research group (ALF-USAL) at University of Salamanca (https://laser.usal.es/alf/en/home/). The candidate will find a dynamic and international working environment, and will enrol in the theoretical group. ALF-USAL is an interdisciplinary Optics research group with expertise in both theory (strong-field physics, nonlinear optics, ultrafast phenomena, attosecond science) and experiments (ultrashort pulse characterization, pulse shaping, photonic crystals, ultrashort micro-machining). The candidate will explore the generation and ultrashort structured pulses and their application in ultrafast magnetism, an emerging field that is opening exciting scenarios in laser-matter interaction at the most fundamental level, merging the fields of Optics and Magnetism.

Some of the recent results have been published in high impact factor scientific journals:

-“Generation of extreme-ultraviolet beams with time-varying orbital angular momentum”, L. Rego, K. M. Dorney, N. J. Brooks, Q. Nguyen, C-T. Liao, J. San Román, D. E. Couch, Allison Liu, E. Pisanty, M. Lewenstein, L. Plaja, H. C. Kapteyn, M. M. Murnane, C. Hernández-García, Science 364, eaaw9486 (2019). Highlighted in the media:

Physicists discover croissant-shaped twists of light. National Geographic (USA)
Twisted light gains angular momentum through ‘self-torque’. PhysicsWorld (UK)
Descubierta una nueva propiedad de la luz. El País (Spain)
Físicos españoles descubren una nueva propiedad de la luz. El Mundo (Spain)

-“Controlling the polarization and vortex charge of attosecond high-harmonic beams via simultaneous spin-orbit momentum conservation”, K. M. Dorney, L. Rego, N. Brooks, J. San Román, C-T. Liao, J. L. Ellis, D. Zusin, C. Gentry, Q. Nguyen, J. M. Shaw, A. Picón, L. Plaja, H. C. Kapteyn, M. M. Murnane, C. Hernández-García, Nature Photonics 13, 123–130 (2019).

-“Extreme-Ultraviolet Vector-Vortex Beams from High Harmonic Generation“, Alba de las Heras, Alok P. Pandey, Julio San Román, Javier Serrano, Elsa Baynard, Guillaume Dovillaire, Moana Pittman, Charles Durfee, Luis Plaja, Sophie Kazamias, Olivier Guilbaud, Carlos Hernández-García, Optica 9, 71-79 (2022).

-“Necklace-structured high harmonic generation for low-divergence, soft X-ray harmonic combs with tunable line spacing”, Laura Rego, Nathan J. Brooks, Quynh L. D. Nguyen, Julio San Román, Iona Binnie, Luis Plaja, Henry C. Kapteyn, Margaret M. Murnane, Carlos Hernández-García, Science Advances 8, eabj7380 (2022).

Job profile

The candidate will explore the application of Artificial Intelligence to the Physics behind the generation of ultrashort structured pulses, an emerging field that is opening exciting scenarios in laser-matter interaction at the most fundamental level, merging the fields of Optics and Computing Sciences. The candidate will be advised thus by two experts in each of those fields:

Dr. Javier Serrano (expert in high performance computing, artificial intelligence)
Dr. Carlos Hernández-García (expert in ultrashort structured laser pulses and nonlinear optics)

Job Functions

Development and implementation of theoretical methods to describe the interaction of femtosecond and attosecond structured laser pulses with atomic and solid systems.
Usage of Artificial Intelligence libraries like Keras / Tensorflow for the design, training and application of neural networks to the generation of ultrashort structured pulses.
Development and improvement of software using C/C++ or Fortran to simulate high harmonic generation, taking advantage of HPC resources and technologies like OpenMP, MPI and CUDA.
Application of the developed codes to explore the limits of sub-attosecond pulse generation, with possibilities to interact with experimental collaborators.

Candidate Requirements

University degree in Physics or Computing Sciences.
Master program, Physics-related or Computing Sciences-related.
Programming skills in Python, C/C++ and/or Fortran.
Advanced level of English: higher than B2 according to the Common European Framework of Reference for Languages or equivalent.
Candidates should be able to demonstrate a promising track record of achievements appropriate to their career stage.

Contract conditions

Type of contract:
- PhD contract.
- Limited to 3,5 years, until the end of the project. Contract to be renewed annually.
- Full-time employee (37,5 hours a week)
Economic compensation:
- Gross salary of:
  - 1.300 €/month (14 salaries), during the first and second years.
  - 1.384 €/month (14 salaries), during the third year.
- Research Project:
  - ATTOSTRUCTURA, “Structured attosecond pulses for ultrafast nanoscience”, funded by the European Research Council (ERC)
- Workplace:
  - Laser Applications and Photonics Research group (ALF-USAL) at University of Salamanca (https://laser.usal.es/alf/en/home/), Spain.
- Estimated starting date: September 2022.

Interested candidates should send a CV (maximum 3 pages), a complete list of grades during his/herdegree and Master program, a personal statement with interests and reasons for applying, and two recommendation letters to Dr. Carlos Hernández-García at alf@usal.es.

For further information and inquiries see Euraxess web page, or contact Dr. Carlos Hernández-García at alf@usal.es.

SELECTION PROCESS

The selection process is governed by the principles of publicity, equality, merit, and ability, constituting the effect one selecting body composed of representatives of the group of research of USAL.

The selection process will consist of two phases:

Analysis phase and curricular value of all nominations received, classified on the basis of better adaptation of the Curriculum vitae to the profile established and compliance with the requirements.
Personal interview: the three candidates with the highest scores in the Phase 1 will be selected for a personal interview.

SELECTION COMMISSION

The selection commission will be made up of the two co-advisors, Dr. Javier Serrano and Dr. Carlos Hernández-García, and one member of the research team Laser Applications and Photonics Research group (ALF-USAL) at Universidad de Salamanca.

More information about the project, the position and the application process can be found Euraxess web page.

17 February, 2022 admin Attostructura_En, Job position, Post_Eng No comments

Innovadores supplement of El Mundo echoes the new research into ultraviolet structured light

The newspaper El Mundo in its supplement Innovadores Castilla y León publishes a report on the new investigation being carried out by the ALF – USAL Group.

This research demonstrates the production of a type of laser beam in the extreme ultraviolet with a special design in phase and polarization.

In this type of beam, the polarization distribution is linked to the phase structure. These light forms are called vector vortices, because the structure is analogous to that of a whirlpool with different directions of vibration. It is, therefore, a light beam that combines the properties of the orbital angular momentum of light associated with the optical vortices with those of the spin angular momentum of the light particles, which defines the polarization.

The study from which the results presented in the publication have been obtained is the result of the collaboration between the ALF – USAL Group with the Paris-Saclay University and the Colorado School of Mines and is part of the European project ERC ATTOSTRUCTURA (851201)

You can read the article below and consult the review published on the article on our website.

9 February, 2022 admin Attostructura_En, Press release No comments

Attostructura Seminar – Structuring ultrafast laser light through highly nonlinear physics

On February 2nd, Carlos Hernández García, Ramón y Cajal researcher, member of the Laser and Photonic Applications research group and principal investigator of the Attostructura project (ERC 851201) gave the seminar “Structuring ultrafast laser light through highly nonlinear physics” within the cycle of seminars of the Rocasolano Institute of the CSIC.

The degree of control we have achieved over the manipulation of light is truly amazing. Initiated by our Greek ancestors using mirrors to guide light, we live in a world where the most advanced laser technology allows us to create and sculpt light beams with great precision. In particular, nowadays we can create ultrashort attosecond pulses (with durations of trillionths of a second), of very high frequencies (up to the soft X-rays), and with increasingly complex spatial structures thanks to our ability to harness their angular momentum. In this talk we will review our recent work in the generation of structured ultrashort laser pulses. Thanks to the highly nonlinear process of high harmonic generation, we can tailor the spin and orbital angular momentum properties of extreme ultraviolet/soft x-ray laser pulses directly at their generation. By properly controlling the process of high harmonic generation, from the driving laser beam to the target (gas or solid), different families of structured ultrashort laser beams can be created: self-torqued beams, vector-vortex beams, tunable high-frequency combs, or hexagonal harmonic beams. These new optical tools allow us to fantasize of new laser-matter interaction processes at the nanoscale, whose physical laws are yet to be discovered. For example, structured laser pulses offer an appealing alternative to study sub-femtosecond magnetization dynamics, where a complete understanding of the electronic and spin interactions remains unexplored

You can see the full video of the seminar on this page or on Youtube channel of the Rocasolano Institute.

3 February, 2022 admin Attostructura_En, Seminar, Video No comments

The University of Salamanca leads a pioneering international research project on ultraviolet structured light

Several media outlets have echoed the publication of a new research article by the ALF – USAL Group in the prestigious Optica magazine. It demonstrates the production of a type of laser beam in the extreme ultraviolet with a special design in phase and polarization.

In this type of beam, the polarization distribution is linked to the phase structure. These light forms are called vector vortices, because the structure is analogous to that of a whirlpool with different directions of vibration. It is, therefore, a light beam that combines the properties of the orbital angular momentum of light associated with the optical vortices with those of the spin angular momentum of the light particles, which defines the polarization.

The authors explain that “the fundamental idea is to control the properties of ultraviolet light by acting on the initial infrared light, thanks to the fact that all the information is encoded in the physical laws of conservation.” In fact, in this study a new conserved quantity is also discovered in the harmonic generation process, the Pancharatnam topological charge, which includes in its definition both the spin and the orbital angular momentum of the light beam.

The study from which the results presented in the publication have been obtained is the result of the collaboration between the ALF – USAL Group with the Paris-Saclay University and the Colorado School of Mines and is part of the European project ERC ATTOSTRUCTURA (851201)

Full report can be read at Salamanca24horas or Divulgación Científica de la USAL web page.

Article review published on the article can be consulted on our website.

17 January, 2022 admin Attostructura_En, Press release No comments

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