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

Abstract

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 1×10 9 photons/s approximately with a resolving power E/∆E ≈ 36. This source provides an ultrashort tunable monochromatic XUV beam for ultrafast studies of electronic and structural dynamics in a large variety of matters.

Minimum structure of high-harmonic spectra from aligned O2 and N2 molecules*

“…The experimental setup to generate harmonics has been described in our previous works. [21,35] We used a 1-kHz Ti: sapphire laser system, providing 6-mJ 35-fs pulses at 800 nm. The output laser pulse was divided into two parts.…”

Direct Coulomb explosion of N2O2+ induced by monochromatic extreme ultraviolet photons at 38.5 eV*

“…This intense infrared laser beam is then focused into a 5-cm long, 150-µm-diameter hollow fiber filled with argon gas to generate extreme ultraviolet (EUV) light via high harmonic generation (HHG). [24][25][26] After the fiber, a set of grating and pinhole are used to spectrally select the EUV photons and the monochromatic photon energy is determined from the photoelectron spectra in single ionization of helium whose binding energy is about 24.6 eV. Eventually, EUV light of ∼ 38.5 eV (25th harmonic) with a bandwidth of about 0.4 eV can be obtained and the flux converted from the photo diode is about 10 9 -10 10 photons/s.…”

Quantum interference of multi-orbital effects in high-harmonic spectra from aligned carbon dioxide and nitrous oxide*

“…The experimental setup used for generation and detection of HHG has already been described in our previous work. [32][33][34] Briefly, a Ti: sapphire laser system operating at 1 kHz repetition was used to deliver ∼ 35 fs pulses centered at 800 nm. The output pulse is divided into two parts by using a 30 : 70 beam splitter.…”