A tunable XUV monochromatic light source based on the time preserving grating selection of high-order harmonic generation

We accomplish a laboratory facility for producing a femtosecond XUV coherent monochromatic radiation with a broad tunable spectral range of 20 eV–75 eV. It is based on spectral selected single-order harmonics from intense laser driven high harmonic generation in gas phase. The time preserving for the selected harmonic radiation is achieved by a Czerny–Turner type monochromator designed with a conical diffraction grating mount for minimizing the time broadening caused by grating diffraction and keeping a relatively high diffraction efficiency. Our measurement shows that the photon flux of the 23-order harmonic (H23) centered at 35.7 eV is 1×10⁹ photons/s approximately with a resolving power E/ΔE≈36. This source provides an ultrashort tunable monochromatic XUV beam for ultrafast studies of electronic and structural dynamics in a large variety of matters.