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Title: Observation of Reverse Saturable Absorption of an X-ray Laser

A nonlinear absorber in which the excited state absorption is larger than the ground state can undergo a process called reverse saturable absorption. It is a well-known phenomenon in laser physics in the optical regime, but is more difficult to generate in the x-ray regime, where fast nonradiative core electron transitions typically dominate the population kinetics during light matter interactions. Here, we report the first observation of decreasing x-ray transmission in a solid target pumped by intense x-ray free electron laser pulses. The measurement has been made below the K-absorption edge of aluminum, and the x-ray intensity ranges are 10 16 –10 17 W=cm 2. It has been confirmed by collisional radiative population kinetic calculations, underscoring the fast spectral modulation of the x-ray pulses and charge states relevant to the absorption and transmission of x-ray photons. The processes shown through detailed simulations are consistent with reverse saturable absorption, which would be the first observation of this phenomena in the x-ray regime. These light matter interactions provide a unique opportunity to investigate optical transport properties in the extreme state of matters, as well as affording the potential to regulate ultrafast x-ray freeelectron laser pulses.
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  1. Inst. of Basic Science, Gwangju (Korea, Republic of); Gwangju Inst. of Science and Technology (Korea, Republic of)
  2. Intl Atomic Energy Agency (IAEA), Vienna (Austria)
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  4. Academy of Sciences of the Czech Republic (ASCR), Prague (Czech Republic). Inst. of Physics
  5. Univ. of Oxford (United Kingdom)
  6. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  7. Univ. of California, Berkeley, CA (United States)
  8. Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
  9. European X-ray Free-Electron Laser (XFEL), Schenefeld (Germany)
Publication Date:
Grant/Contract Number:
IBS-R012-D1; NRF-2016R1A2B4009631; NRF-2015R1A5A1009962; EP/H035877/1; EP/L000849/1; AC02-76SF00515
Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 119; Journal Issue: 7; Journal ID: ISSN 0031-9007
American Physical Society (APS)
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1375496