PhD position in Theory of generation of bright attosecond pulses at King's College London, UK

The creation of the shortest duration, attosecond, light pulses has been celebrated by the Nobel Prize in Physics 2023 [1]. The application of such pulses increases the temporal resolution that physical processes, such as electronic dynamics in atoms, molecules and condensed matter, can be observed with. Even more valuable is to make these ultrashort pulses strong enough to be applicable at a wider scale in the lab and to a broader range of dynamics.

One of the main ways to produce attosecond light pulses is via the interaction of an intense laser pulse with a highly nonlinear medium (atoms, molecules and solids), when many photons of the initial laser light can be converted into photons with energy which is dozens, hundreds or even thousands of times the photon energy in the initial laser pulse, a process called high-order harmonic generation (HHG) [1,2,3].

There are two ways to increase the brightness of the emitted HHG light: either playing with a choice of the generating medium (microscopically) or via taking advantage of the propagation conditions in the generating medium (macroscopically). It has been recently found out [4] that the macroscopic growth of the brightness of the HHG light is fundamentally limited. This hurdle can be jumped over if we switch from the common and well-understood HHG process to its high-order cousin – high-order frequency mixing (HFM) – by complementing the generating strong laser field with weaker low-frequency laser light [4,5].

This project will be devoted to a detailed study of the HFM process and to the optimisation of the generation conditions, such as laser frequencies, intensities, relative phase and pulse durations, which would result in the production of the shortest and brightest light pulses.

The activities involved in the project will include:

• Theoretical analysis, using analytical and numerical methods, of propagation of XUV light and its generation via high-order nonlinear processes
• Numerically model signals of HHG and HFM in the spectral and temporal domains
• Development and optimisation of software for numerical calculations, including running pre-built Mathematica (potentially Matlab, Fortran and Python) codes and their development
• Collaboration with experimental groups to propose new experiments and analyse existing data
• Attendance of conferences, workshops and summer schools

Candidate requirements:

Candidates will be judged according to how well they meet the following criteria:

• A passion for research, and eagerness to learn new skills
• Creativity and a collaborative spirit, the ability to work in a team
• Ability to formulate and test hypotheses, to generate and analyse numerical data
• The ability to clearly communicate your ideas to your colleagues and to people beyond our research team (please note that there are formal requirements on English language qualifications, which are detailed in https://www.kcl.ac.uk/study/postgraduate/apply/entry-requirements/english-language.aspx (Band D))
• A first-class honours degree to second class honours upper division (2.1) in Physics or related subjects
• Fluency with analytical methods of theoretical physics and ability to apply mathematical skills to analyse and solve problems
• A background in quantum mechanics, nonlinear optics, or light-matter interaction

The following skills are desirable but not essential:

• Experience with working in a research environment
• Basic knowledge of ultrafast physics and attosecond science
• Ability to program in one or more programming languages, such as Wolfram Language, python, Julia, C++, etc.
• Knowledge of Wolfram Mathematica or other computer algebra systems

Application Deadline: 1 May 2024

For informal enquiries and to discuss the scope of the project, please contact Margarita Khokhlova (margarita.khokhlova@kcl.ac.uk).

More information >>

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References
[1] Nobel Prize in Physics 2023. Press release and scientific background, 2023. https://www.nobelprize.org/prizes/physics/2023/press-release/
[2] D. Villeneuve, “Attosecond Science”, Contemporary Physics 59, 47 (2018).
[3] T. Popmintchev et al., “Bright Coherent Ultrahigh Harmonics in the keV X-ray Regime from Mid-Infrared Femtosecond Lasers”, Science 336, 1287 (2012).
[4] M. Khokhlova, V. Strelkov, “Highly efficient XUV generation via high-order frequency mixing”, New J. Phys. 22, 093030 (2020).
[5] V. A. Birulia, M. A. Khokhlova, V. V. Strelkov, “Macroscopic effects in generation of attosecond XUV pulses via high-order frequency mixing in gases and plasma”, arXiv:2308.02251 (2023)