EUV – X-ray Quantum Optics

Quantum Optics Meets Attosecond Strong Field Physics:

Novel Regimes of Coherent X-ray Generation with Strong Electron Correlation Dynamics and Attosecond Rabi Oscillations

Ultrafast imaging and spectroscopies using coherent EUV – X-ray light based on the nonlinear process of high harmonic generation are already addressing grand challenges in complex molecular systems, plasmas, and advanced nanomaterials. The exquisite quantum control of the attosecond dynamics of the rescattering electrons in this extreme frequency upconversion makes it possible to sculpt the classical and quantum properties of the light with unprecedented tunability of the spectral, spatial, temporal shape, and spin and orbital angular momentum state. The superb coherence of this unique light allows for multi-dimensional imaging at the space-time extreme with 4D resolution of nanometers and femtoseconds, including access to an effective 5th dimension – the periodic table of elements – due to the X-ray absorption fingerprinting with elemental and chemical specificity.

In a new research thrust, Popmintchev LABS and collaborators from Salamanca, Spain, and Vienna, Austria, have uncovered two novel quantum regimes of coherent X-ray generation where the design of the light properties is dominated by the dynamics of the entangled electrons in a simple He atomic system. Interestingly, the physics of these regimes extends beyond the well-established three-step high harmonic model.

In the first regime, using strong UV laser fields, the entangled electron dynamics yield a characteristic plateau in the X-ray spectral region, extending well beyond the conventional cutoff. This is due to simultaneous double electron recombination where a single high-energy X-ray photon is emitted only in atomic systems with strongly correlated electrons. This low probability phenomenon paves a way to a sensitive attosecond spectroscopy as a probe of highly correlated interactions, for the first time. Similar physics of high harmonics from solids might be able to characterize electron correlations in phase transition materials and nanosystems of relevance to quantum computing and superconductivity.

In the second extreme regime, using intense EUV driving fields tuned to a resonance frequency of He can result in very bright harmonic emission in the X-ray regime. Favorable quantum dynamics of the electron wavepackets, and phase and group velocity matching of the light fields enhance the X-ray yield. Furthermore, record-fast attosecond Rabi oscillations are predicted, for the first time, to suppress the depletion of the ground state, which otherwise terminates the emission of X-ray photons.

These new advances in quantum control over the coherent X-ray emission enable first spectroscopic insights into complex entangled electron dynamics and applications in nanoscience and quantum technology.

  1. Siyang Wang, Jieyu Yan, Alba de las Heras, Sirius Song, Aleksandar Prodanov, Zhihan Wu, Carlos Hernández-García, Luis Plaja, Dimitar Popmintchev, Tenio Popmintchev, “Double Electron Recombination in Strongly Correlated System: Extended Secondary Plateau in UV-Driven High Harmonic Generation in the Soft X-ray Regime”, Frontiers in Optics + Laser Science 2023 (FiO, LS) Technical Digest Series (Optica Publishing Group, 2023), paper FTh3C.6. https://doi.org/10.1364/FIO.2023.FTh3C.6
  2. Siyang Wang, Jieyu Yan, Alba de las Heras, Sirius Song, Aleksander Prodanov, Zhihan Wu, Carlos Hernández-García, Luis Plaja, Dimitar Popmintchev, and Tenio Popmintchev, “Quantum Optics Regime of Coherent X-ray Generation with Strongly Correlated Electron Dynamics in Helium Atoms”, (to be submitted) (2023).
  3. Alba de las Heras, Carlos Hernández-García, Dimitar Popmintchev, Tenio Popmintchev, Luis Plaja, “Quantum Optics Regime of Coherent EUV – X-ray Generation with Attosecond Rabi Oscillations using Extreme UV Lasers”, (to be submitted) (2023).
  4. A de las Heras, C Hernández-García, J Serrano, T Popmintchev, L Plaja, “Attosecond Rabi oscillations in bright high harmonic emission in the X-ray regime driven by XUV pulses’, Frontiers in Optics, FTu1C. 3, (2022). https://doi.org/10.1364/FIO.2022.FTu1C.3
  5. Alba de las Heras, Carlos Hernández-García, Javier Serrano, Tenio Popmintchev, and Luis Plaja, “Attosecond Rabi oscillations revealed in EUV-driven high harmonic spectroscopy”, Conference on Lasers and Electro-Optics/Europe (CLEO/Europe 2023) and European Quantum Electronics Conference (EQEC 2023), Technical Digest Series (Optica Publishing Group, 2023), Paper ee_3_5. https://opg.optica.org/abstract.cfm?URI=EQEC-2023-ee_3_5