WE2C —  Working Group C: Compact Light Sources   (30-Aug-23   11:00—12:30)
Chair: C.-Y. Tsai, HUST, Wuhan, People’s Republic of China
Paper Title Page
WE2C1
 Population Inversion X-ray Laser Oscillator at LCLS and LCLS-II  
 
  • A. Halavanau, A. Aquila, U. Bergmann, C. Pellegrini
    SLAC, Menlo Park, California, USA
  • A.I. Benediktovitch
    DESY, Hamburg, Germany
  • N. Majernik
    UCLA, Los Angeles, California, USA
  • N. Rohringer
    Max Planck Institute for the Physics of Complex Systems, Dresden, Germany
  • N.B. Welke
    UW-Madison/PD, Madison, Wisconsin, USA
  
  The advancement of X-ray Free Electron Lasers (XFELs) has created revolutionary new research opportunities, owing to their high peak and average power, transverse coherence, and short pulse duration. Despite their remarkable capabilities, XFEL pulses lack longitudinal coherence and are not transform-limited, which limits their utilization, e.g. in quantum optics and precision interferometry. We explore the development of coherent, transform-limited pulses through alternative strategies, namely, X-ray lasers based on population inversion. We propose a novel approach relying on the principle of stimulated emission in the hard X-ray regime, using the XFEL as a pump. We will specifically discuss the case of the X-ray Laser Oscillator (XLO) at the LCLS copper linac and the planed LCLS-II-HE. Our recent work has shown the feasibility and performance characteristics of these systems, which can operate over a broad wavelength range from 5 to 12 keV. Future applications at LCLS-II-HE might allow for transform-limited XLO pulses with repetition rates up to tens of kHz. We show that XLO is experimentally feasible and discuss its projected performance and photon pulse properties operating at the Copper K-alpha1 line. Finally, we discuss possible first experiments with XLO.  
slides icon Slides WE2C1 [2.756 MB]  
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WE2C2
 Harmonic Generation from keV-electron-excited Nano-grating  
 
  • Y.-C. Huang
    NTHU, Hsinchu, Taiwan
  
  Funding: MOST 111-2221-E-007-001, Taiwan
There has been a recent interest in using free electrons to interact with photonic structures and generate light. The envisaged dielectric accelerator on a chip is a low-current electron source driven by a laser. The generated electron beam contains a few electrons in each optical cycle repeating at the driver laser frequency. We perform a feasibility study in this paper on the harmonic generation of a periodic array of single electrons with keV energy atop a dielectric grating waveguide. The device is a 31 um long silicon grating on top of a glass substrate, having a 400 nm thickness and 310-nm period. The structure is designed to have a Bragg resonance at 1.5 um in wavelength or 0.2 PHz in frequency for the radiation mode. We use the simulation code CST to study the radiation from a periodic array of 25 electrons. The electrons have 50 keV energy, injected one by one at 0.1 PHz at 100 nm above the grating. The transit time of the 50 keV electrons over the 31 um long silicon grating is 0.25 ps. Cherenkov radiation is guided in the silicon waveguide layer. Smith-Purcell (SP) radiation is generated in the vacuum region above the grating. We show in simulation a ring-down of the generated coherent radiations from both ends of the grating waveguide, indicating that a grating waveguide is a good Bragg resonator. The field pattern in the waveguide region satisfies the Bragg condition, i.e. structure periodicity = half of the longitudinal wavelength. The Fourier transform of the generated radiation wave has a narrow radiation spectrum at 0.2 PHz. A discrete spectrum of SP radiation mediated by the waveguide modes is also observed from simulation in the vacuum space above the grating waveguide. This study shows the feasibility of generating harmonic radiation from a nano-photonic structure driven by keV periodic electrons. 		 
slides icon Slides WE2C2 [3.982 MB]  
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