Abstract
The development of linac–based narrow–band THz sources with sub–picosecond, mu J-level radiation pulses is in demand from the scientific community. Intrinsically monochromatic emitters such as coherent Smith–Purcell radiation sources appear as natural candidates. However, the lack of broad spectral tunability continues to stimulate active research in this field. We hereby present the first experimental investigation of coherent grating diffraction radiation (GDR), for which comparable radiation intensity with central frequency fine–tuning in a much wider spectral range has been confirmed. Additionally, the approach allows for bandwidth selection at the same central frequency. The experimental validation of performance included the basic spectral, spatial and polarization properties. The discussion of the comparison between GDR intensity and other coherent radiation sources is also presented. These results further strengthen the foundation for the design of a tabletop wide–range tunable quasi–monochromatic or multi–colour radiation source in the GHz–THz frequency range.
Highlights
The development of linac–based narrow–band THz sources with sub–picosecond, μJ-level radiation pulses is in demand from the scientific community
We demonstrate the first experimental observation of coherent grating diffraction radiation (GDR) which includes the investigation of the basic spectral, spatial and polarization properties in addition to a discussion on GDR intensity in comparison with coherent Smith-Purcell radiation (SPR) and coherent diffraction radiation (CDR)
We measured the spectral–angular distribution and polarization properties of the radiation produced by the 8 MeV, 25 pC single electron bunch with 0.15 mm rms length passing below the 4 mm period, 30 × 60 mm[2], N0 = 15, echelette profile grating (Fig. 1b,c)
Summary
The development of linac–based narrow–band THz sources with sub–picosecond, μJ-level radiation pulses is in demand from the scientific community. Implementation of large angle radiation emission may be considered in a “diffraction radiation”–like arrangement This should lead to different radiation polarization maps, intensities and directivity profiles, the approach offers wide–range monochromatic spectral tunability which still follows Eq 1. Radiation generated in this case, by analogy with the grating transition radiation[22,23,24], has significant spectral tunability but without the drawback of the destructive interaction of the electron beam with the grating material. This radiation is referred to as the “grating diffraction radiation” (GDR)
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